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a
Mixed-Signal Front-End (MxFETM) Processor for Broadband Communications AD9860/AD9862*
FUNCTIONAL BLOCK DIAGRAM
VIN+A VIN-A 1x PGA ADC BYPASSABLE LOW-PASS DECIMATION FILTER VIN+B VIN-B SIGDELT 1x PGA ADC RxB DATA [0:11] HILBERT FILTER RxA DATA [0:11]
FEATURES Mixed-Signal Front-End Processor with Dual Converter Receive and Dual Converter Transmit Signal Paths Receive Signal Path Includes: Two 10-/12-Bit, 64 MSPS Sampling A/D Converters with Internal or External Independent References, Input Buffers, Programmable Gain Amplifiers, Low-Pass Decimation Filters, and a Digital Hilbert Filter Transmit Signal Path Includes: Two 12-/14-Bit, 128 MSPS D/A Converters with Programmable Full-Scale Output Current, Channel Independent Fine Gain and Offset Control, Digital Hilbert and Interpolation Filters, and Digitally Tunable Real or Complex Up-Converters Delay-Locked Loop Clock Multiplier and Integrated Timing Generation Circuitry Allow for Single Crystal or Clock Operation Programmable Output Clocks, Serial Programmable Interface, Programmable Sigma-Delta, Three Auxiliary DAC Outputs and Two Auxiliary ADCs with Dual Multiplexed Inputs APPLICATIONS Broadband Wireless Systems Fixed Wireless, WLAN, MMDS, LMDS Broadband Wireline Systems Cable Modems, VDSL, PowerPlug Digital Communications Set-Top Boxes, Data Modems GENERAL DESCRIPTION
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LOGIC LOW
AD9860/AD9862
SPI REGISTERS SPI INTERFACE
AUX_DAC_A AUX_DAC_B AUX_DAC_C
AUX DAC AUX DAC AUX DAC Rx PATH TIMING Tx PATH TIMING AUX ADC
CLOCK DISTRIBUTION BLOCK
DLL 1 ,2 ,4
OSC1 OSC2
AUX_ADC_A1 AUX_ADC_A2 AUX_ADC_B1 AUX ADC AUX_ADC_B2
CLKOUT1 BYPASSABLE DIGITAL QUADRATURE MIXER CLKOUT2
BYPASSABLE DIGITAL QUADRATURE MIXER IOUT+A IOUT-A IOUT+B IOUT-B PGA DAC FS/4 FS/8 PGA DAC
HILBERT FILTER
Tx DATA [0:13]
BYPASSABLE LOW-PASS INTERPOLATION FILTER
NCO
range for both channels. The output data bus can be multiplexed to accommodate a variety of interface types. The AD9860/AD9862 transmit path (Tx) consists of two channels that contain high performance, 12-/14-bit, 128 MSPS digital-to-analog converters (DAC), programmable gain amplifiers (TxPGA), interpolation filters, a Hilbert filter, and digital mixers for complex or real signal frequency modulation. The Tx latch and demultiplexer circuitry can process real or I/Q data. Interpolation rates of 2 and 4 are available to ease requirements on an external reconstruction filter. For single channel systems, the digital Hilbert filter can be used with an external quadrature modulator to create an image rejection architecture. The two 12-/14-bit, high performance DACs produce an output signal that can be scaled over a 20 dB range by the TxPGA. A programmable delay-locked loop (DLL) clock multiplier and integrated timing circuits enable the use of a single external reference clock or an external crystal to generate clocking for all internal blocks and also provides two external clock outputs. Additional features include a programmable sigma-delta output, four auxiliary ADC inputs and three auxiliary DAC outputs. Device programmability is facilitated by a serial port interface (SPI) combined with a register bank. The AD9860/AD9862 is available in a space saving 128-lead LQFP.
The AD9860 and AD9862 (AD9860/AD9862) are versatile integrated mixed-signal front-ends (MxFE) that are optimized for broadband communication markets. The AD9860/AD9862 are cost effective, mixed signal solutions for wireless or wireline standards based or proprietary broadband modem systems where dynamic performance, power dissipation, cost, and size are all critical attributes. The AD9860 has 10-bit ADCs and 12-bit DACs; the AD9862 has 12-bit ADCs and 14-bit DACs. The AD9860/AD9862 receive path (Rx) consists of two channels that each include a high performance, 10-/12-bit, 64 MSPS analogto-digital converter (ADC), input buffer, Programmable Gain Amplifier (RxPGA), digital Hilbert filter, and decimation filter. The Rx can be used to receive real, diversity, or I/Q data at baseband or low IF. The input buffers provide a constant input impedance for both channels to ease impedance matching with external components (e.g., SAW filter). The RxPGA provides a 20 dB gain
*Protected by U.S.Patent No. 5,969,657; other patents pending. MxFE is a trademark of Analog Devices, Inc.
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Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2002
V V 10%, = = 4 k , 50 Normal Mode, 2 AD9860/AD9862-SPECIFICATIONS (V = 3.3Timing5%, V = 3.3DLL=Setting, fRGain.)128 MHz, f RxPGA = +6 dB Gain, TxPGA +20 dB
A D DAC SET
ADC
= 64 MHz DAC Load,
Tx PARAMETERS 12-/14-BIT DAC CHARACTERISTICS Resolution Maximum Update Rate Full-Scale Output Current Gain Error (Using Internal Reference) Offset Error Reference Voltage (REFIO Level) Negative Differential Nonlinearity (-DNL) Positive Differential Nonlinearity (+DNL) Integral Nonlinearity (INL) Output Capacitance Phase Noise @ 1 kHz Offset, 6 MHz Tone Crystal and OSC IN Multiplier Enabled at 4 Output Voltage Compliance Range TRANSMIT TxPGA CHARACTERISTICS Gain Range Step Size Accuracy Step Size Tx DIGITAL FILTER CHARACTERISTICS Hilbert Filter Pass Band (<0.1 dB Ripple) 2 /4 Interpolator Stop Band2 DYNAMIC PERFORMANCE (AOUT = 20 mA FS, f = 1 MHz) Differential Phase Differential Gain AD9860 Signal-to-Noise Ratio (SNR) AD9860 Signal-to-Noise and Distortion Ratio AD9860 Total Harmonic Distortion (THD) AD9860 Wideband SFDR (to Nyquist) 1 MHz Analog Out, IOUT = 2 mA 1 MHz Analog Out, IOUT = 20 mA 6 MHz Analog Out, IOUT = 20 mA AD9860 Narrowband SFDR (1 MHz Window) 1 MHz Analog Out, IOUT = 2 mA 1 MHz Analog Out, IOUT = 20 mA AD9862 Signal-to-Noise Ratio (SNR) AD9862 Signal-to-Noise and Distortion Ratio AD9862 Total Harmonic Distortion (THD) AD9862 Wideband SFDR (to Nyquist) 1 MHz Analog Out, IOUT = 2 mA 1 MHz Analog Out, IOUT = 20 mA 6 MHz Analog Out, IOUT = 20 mA AD9862 Narrowband SFDR (1 MHz Window) 1 MHz Analog Out, IOUT = 2 mA 1 MHz Analog Out, IOUT = 20 mA Rx PARAMETERS RECEIVE BUFFER Input Resistance (Differential) Input Capacitance (Each Input) Maximum Input Bandwidth (-3 dB) Analog Input Range (Best Noise Performance) Analog Input Range (Best THD Performance) RECEIVE PGA CHARACTERISTICS Gain Error Gain Range Step Size Accuracy Step Size Input Bandwidth (-3 dB, Rx Buffer Bypassed) 10-/12-BIT ADC CHARACTERISTICS Resolution Maximum Conversion Rate
Temp NA Full 25C 25C 25C 25C 25C 25C 25C 25C Full 25C 25C 25C Full Full 25C 25C Full Full Full 25C 25C 25C 25C 25C Full Full Full 25C 25C 25C 25C 25C
Test Level NA I I I I III III III III III II III III III II II III III I I I III I III III I I I I III I III III I
Min
AD9860/AD9862 Typ 12/14
Max
Unit Bits MSPS mA %FS %FS V LSB LSB LSB pF dBc/Hz V dB dB dB
128 2 -5.5 -1 1.15
+0.5 0.0 1.22 -0.5/-0.5 1/2 1/ 3 5 -115
20 +5.5 +1 1.28
-0.5 20 0.1 0.08 12.5
+1.5
38 38 <0.1 <1 70.7 66.1 -74.5 70.6 75 75 70.2 90 72.0 69.8 -75.5 70.6 76.0 76.0 70.2 90
% fDATA1 % fDATA Degree LSB dB dB dB dBc dBc dBc dBc dBc dB dB dB dBc dBc dBc dBc dBc
68.2 62.5
-64.0
64.4
83 68.9 64.75
-65.0
64.9
83
Full Full Full Full Full 25C 25C 25C 25C 25C NA Full
III III III II II I I I I III NA I
200 5 140 2 1 0.3 20 0.2 1 250 10/12 64
W pF MHz V p-p Diff V p-p Diff dB dB dB dB MHz Bits
19
21
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AD9860/AD9862
Rx PARAMETERS (continued) DC ACCURACY Differential Nonlinearity Integral Nonlinearity Offset Error Gain Error Aperture Delay Aperture Uncertainty (Jitter) Input Referred Noise Reference Voltage Error REFT-REFB Error (1 V) Temp 25C 25C 25C 25C 25C 25C 25C 25C Test Level III III III III III III III I I I I I I I I I III III 59.0 56.0 70.3 62.6 62.5 77.09 Min AD9860/AD9862 Typ Max 0.3/ 0.4 1.2/ 5 0.1 0.2 2.0 1.2 250 1 60.66 58.0 -76.5 81.0 64.2 64.14 -79.22 85.13 >90 >80 4 Unit LSB LSB %FSR %FSR ns ps rms V mV dBc dBc dBc dBc dBc dBc dBc dBc dB dB
AD9860 DYNAMIC PERFORMANCE (AIN = -0.5 dBFS, f = 5 MHz) Signal-to-Noise Ratio 25C Signal-to-Noise and Distortion Ratio 25C Total Harmonic Distortion 25C Spurious Free Dynamic Range 25C AD9862 DYNAMIC PERFORMANCE (AIN = -0.5 dBFS, f = 5 MHz) Signal-to-Noise Ratio 25C Signal-to-Noise and Distortion Ratio 25C Total Harmonic Distortion 25C Spurious Free Dynamic Range 25C CHANNEL-TO-CHANNEL ISOLATION Tx-to-Rx (AOUT = 0 dBFS, fOUT = 7 MHz) Rx Channel Crosstalk (f1 = 6 MHz, f2 = 9 MHz) PARAMETERS CMOS LOGIC INPUTS Logic "1" Voltage, VIH Logic "0" Voltage, VIL Logic "1" Current Logic "0" Current Input Capacitance CMOS LOGIC OUTPUTS (1 mA Load) Logic "1" Voltage, VOH Logic "0" Voltage, VOL POWER SUPPLY Analog Supply Currents Tx (Both Channels, 20 mA FS Output) Tx Powered Down Rx (Both Channels, Input Buffer Enabled) Rx (Both Channels, Input Buffer Disabled) Rx (32 MSPS, Low Power Mode, Buffer Disabled) Rx (16 MSPS, Low Power Mode, Buffer Disabled) Rx Path Powered Down DLL Digital Supply Current AD9860 Both Rx and Tx Path (All Channels Enabled) 2 Interpolation, fDAC = fADC = 64 MSPS AD9862 Both Rx and Tx Path (All Channels Enabled) 2 Interpolation, fDAC = fADC = 64 MSPS Tx Path (fDAC = 128 MSPS) Processing Blocks Disabled 4 Interpolation 4 Interpolation, Coarse Modulation 4 Interpolation, Fine Modulation 4 Interpolation, Coarse and Fine Modulation 25C 25C 25C 25C 25C 25C 25C 25C 25C
-70.5
-73.2
II II II II III II II
DRVDD - 0.7 0.4 12 12 3 DRVDD - 0.6 0.4
V V A A pF V V
25C 25C 25C 25C 25C 25C 25C 25C
I I I III III III I III
70 2.5 275 245 155 80 5.0 12
76 5.0 307
6.0
mA mA mA mA mA mA mA mA
25C 25C 25C 25C 25C 25C 25C
I I III III III III III
92 104 45 90 110 110 130
112 124
mA mA mA mA mA mA mA
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AD9860/AD9862
PARAMETERS (continued) POWER SUPPLY (continued) Rx Path (fADC = 64 MSPS) Processing Blocks Disabled Decimation Filter Enabled Hilbert Filter Enabled Hilbert and Decimation Filter Enabled Temp Test Level Min AD9860/AD9862 Typ Max Unit
25C 25C 25C 25C
III III III III
9 15 16 18.5
mA mA mA mA
NOTES 1 % fDATA refers to the input data rate of the digital block. 2 Interpolation filter stop band is defined by image suppression of 50 dB or greater. Specifications subject to change without notice.
TIMING CHARACTERISTICS
(20 pF Load) Minimum Reset Pulsewidth Low (tRL) Digital Output Rise/Fall Time DLL Output Clock DLL Output Duty Cycle Tx-/Rx-Interface (See Figures 11 and 12) TxSYNC/TxIQ Setup Time (tTx1, tTx3) TxSYNC/TxIQ Hold Time (tTx2, tTx4) RxSYNC/RxIQ/IF to Valid Time(tRx1, tRx3) RxSYNC/RxIQ/IF Hold Time (tRx2, tRx4) Serial Control Bus (See Figures 1 and 2) Maximum SCLK Frequency (fSCLK) Minimum Clock Pulsewidth High (tHI) Minimum Clock Pulsewidth Low (tLOW) Maximum Clock Rise/Fall Time Minimum Data/SEN Setup Time (tS) Minimum SEN/Data Hold Time (tH) Minimum Data/SCLK Setup Time (tDS) Minimum Data Hold Time (tDH) Output Data Valid/SCLK Time (tDV) AUXILARY ADC Conversion Rate Input Range Resolution AUXILARY DAC Settling Time Output Range Resolution ADC TIMING Latency (All Digital Processing Blocks Disabled) DAC Timing Latency (All Digital Processing Blocks Disabled) Latency (2 Interpolation Enabled) Latency (4 Interpolation Enabled) Additional Latency (Hilbert Filter Enabled) Additional Latency (Coarse Modulation Enabled) Additional Latency (Fine Modulation Enabled) Output Settling Time (TST) (to 0.1%)
Specifications subject to change without notice.
Temp NA 25C 25C 25C 25C 25C 25C 25C Full Full Full Full Full Full Full Full Full 25C 25C 25C 25C 25C 25C 25C 25C 25C 25C 25C 25C 25C 25C
Test Level NA III III III III III III III III III III III III III III III III III III III III III III III III III III III III III III
Min 5 2.8 32
AD9860/AD9862 Typ Max 4 128 50
Unit Clock Cycles ns MHz % ns ns ns ns MHz ns ns ms ns ns ns ns ns MHz V Bits ms V Bits Cycles Cycles Cycles Cycles Cycles Cycles Cycles ns
3 3 5.2 0.2 16 30 30 1 25 0 25 0 30 1.25 3 10 8 3 8 7 3 30 72 36 5 8 35
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AD9860/AD9862
ABSOLUTE MAXIMUM RATINGS 1 EXPLANATION OF TEST LEVELS
Power Supply (VAS, VDS) . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 V Digital Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . 5 mA Digital Inputs . . . . . . . . . . . . . . . . -0.3 V to DRVDD + 0.3 V Analog Inputs . . . . . . . . . . . . . . -0.3 V to AVDD (IQ) + 0.3 V Operating Temperature2 . . . . . . . . . . . . . . . . . -40 C to +70 C Maximum Junction Temperature . . . . . . . . . . . . . . . . . 150 C Storage Temperature . . . . . . . . . . . . . . . . . . . -65 C to +150 C Lead Temperature (Soldering 10 sec) . . . . . . . . . . . . . . 300 C
NOTES 1 Absolute maximum ratings are limiting values, to be applied individually, and beyond which the serviceability of the circuit may be impaired. Functional operability under any of these conditions is not necessarily implied. Exposure to absolute maximum rating conditions for extended periods of time may affect device reliability. 2 The AD9860/AD9862 have been characterized to operate over the industrial temperature range (-40 C to +85 C) when operated in Half Duplex Mode.
I.
Devices are 100% production tested at 25C and guaranteed by design and characterization testing for the extended industrial temperature range (-40C to +70C). Parameter is guaranteed by design and/or characterization testing.
II.
III. Parameter is a typical value only. NA. Test level definition is not applicable.
THERMAL CHARACTERISTICS Thermal Resistance
128-Lead LQFP
JA
= 29C/W
ORDERING GUIDE
Model AD9860BST AD9862BST AD9860PCB AD9862PCB
Temperature Range -40C to +70C* -40C to +70C*
Package Description 128-Lead Low Profile Plastic Quad Flatpack (LQFP) 128-Lead Low Profile Plastic Quad Flatpack (LQFP) Evaluation Board with AD9860 Evaluation Board with AD9862
Package Option ST-128B ST-128B
*The AD9860/AD9862 have been characterized to operate over the industrial temperature range (-40 C to +85 C) when operated in Half Duplex Mode.
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD9860/AD9862 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
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AD9860/AD9862
PIN CONFIGURATION
128 AUX_ADC_A2 127 AUX_ADC_REF 126 AUX_ADC_B1 125 AUX_ADC_B2
120 REFB_A
121 REFT_A
115 VIN+A
116 AGND
109 AGND
107 VIN+B
114 VIN-A
108 VIN-B
122 AGND
119 AGND
113 AGND
112 AGND
110 AGND
106 AGND
124 AVDD
118 AVDD
105 AVDD
103 AGND
123 AVDD
117 AVDD
104 AVDD
111 VREF
AUX_ADC_A1 AGND AVDD AVDD SIGDELT AUX_DAC_A AUX_DAC_B AUX_DAC_C AGND
1 2 3 4 5 6 7 8 9
PIN 1 IDENTIFIER
102 REFB_B 101 REFT_B 100 AGND 99 AVDD 98 AVDD 97 AUX_SPI_csb 96 AUX_SPI_clk 95 AUX_SPI_do 94 DGND 93 DVDD 92 RxSYNC 91 D9/D11B (MSB) 90 D8/D10B 89 D7/D9B 88 D6/D8B 87 D5/D7B 86 D4/D6B 85 D3/D5B 84 D2/D4B 83 D1/D3B 82 D0/D2B 81 NC/D1B 80 NC/D0B 79 D9/D11A (MSB) 78 D8/D10A 77 D7/D9A 76 D6/D8A 75 D5/D7A 74 D4/D6A 73 D3/D5A 72 D2/D4A 71 D1/D3A 70 D0/D2A 69 NC/D1A 68 NC/D0A 67 DGND 66 DVDD 65 CLKOUT1
TxSYNC 51 DVDD 53 SCLK 54 SDO 55 SDIO 56 SEN 57 DGND 58 DVDD 59 DGND 60 DVDD 61 MODE/TxBLANK 62 CLKOUT2 64 Tx9/11 39 Tx8/10 40 DGND 52 RESETB 63 NC/Tx1 49 NC/Tx0 50 Tx7/9 41 Tx6/8 42 Tx5/7 43 Tx4/6 44 Tx3/5 45 Tx2/4 46 Tx1/3 47 Tx0/2 48
DLL_Lock 10 AGND 11 NC 12 AVDD 13 OSC1 14 OSC2 15 AGND 16 CLKSEL 17 AVDD 18 AGND 19 AVDD 20 REFIO 21 FSADJ 22 AVDD 23 AGND 24 IOUT-A 25 IOUT+A 26 AGND 27 AGND 28 IOUT+B 29 IOUT-B 30 AGND 31 AVDD 32 DVDD 33 DGND 34 DGND 35 DVDD 36 Tx11/13 (MSB) 37 Tx10/12 38
AD9860/AD9862
TOP VIEW (Not to Scale)
NC = NO CONNECT
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AD9860/AD9862
PIN FUNCTION DESCRIPTIONS
Pin No.
Mnemonic Receive Pins
Function
Pin No.
Mnemonic Clock Pins
Function
68/70-79 D0A to D9A/D11A 80/82-91 D0B to D9B/D11B 92 RxSYNC 98, 99, AVDD 104, 105, 117, 118, 123, 124, 100, 103, AGND 106, 109, 110, 112, 113, 116, 119, 122, 101 REFT_B 102 107 108 111 114 115 120 121 REFB_B VIN+B VIN-B VREF VIN-A VIN+A REFB_A REFT_A
10-/12-Bit ADC Output of Receive Channel A 10-/12-Bit ADC Output of Receive Channel B Synchronization Clock for Channel A and Channel B Rx Paths Analog Supply Pins
10 11, 16 12 13 14 15 17 64
DLL_Lock AGND NC AVDD OSC1 OSC2 CLKSEL CLKOUT2
Analog Ground Pins 65 CLKOUT1
DLL Lock Indicator Pin DLL Analog Ground Pins No Connect DLL Analog Supply Pin Single Ended Input Clock (or Crystal Oscillator Input) Crystal Oscillator Input Controls CLKOUT1 Rate Clock Output Generated from Input Clock (DLL Multiplier Setting and CLKOUT2 Divide Factor) Clock Output Generated from Input Clock (1 if CLKSEL = 1 or /2 if CLKSEL = 0)
Top Reference Decoupling for Channel B ADC Bottom Reference Decoupling for Channel B ADC Receive Channel B Differential (+) Input Receive Channel B Differential ( ) Input Internal ADC Voltage Reference Receive Channel A Differential ( ) Input Receive Channel A Differential (+) Input Bottom Reference Decoupling for Channel A ADC Top Reference Decoupling for Channel A ADC
Various Pins 1 3, 4, 13 2, 9 5 6 7 8 33, 36, 53, 59, 61, 66, 93 34, 35, 52, 58, 60, 67, 94 54 55 56 57 63 95 96 97 128 126 125 127 AUX_ADC_A1 AVDD AGND SIGDELT AUX_DAC_A AUX_DAC_B AUX_DAC_C DVDD Auxiliary ADC A Input 1 Analog Power Pins Analog Ground Pins Digital Output from Programmable Sigma-Delta Auxiliary DAC A Output Auxiliary DAC B Output Auxiliary DAC C Output Digital Power Supply Pin
DGND
Digital Ground Pin
Transmit Pins 18, 20 23, 32 19, 24, 27, 28, 31 21 22 25 AVDD AGND REFIO FSADJ IOUT-A Analog Supply Pins Analog Ground Pins
Reference Output, 1.2 V Nominal Full-Scale Current Adjust Transmit Channel A DAC Differential ( ) Output 26 IOUT+A Transmit Channel A DAC Differential (+) Output 29 IOUT+B Transmit Channel B DAC Differential (+) Output 30 IOUT-B Transmit Channel B DAC Differential ( ) Output 37-48/50 Tx11/Tx13 12-/14-Bit Transmit DAC Data to Tx0 (Interleaved Data when Required) 51 TxSYNC Synchronization Input for Transmitter 62 MODE/ Configures Default Timing Mode, TxBLANK* Controls Tx Digital Power Down
*The logic level of the Mode/TxBLANK pin at power up defines the default timing mode; a logic low configures Normal Operation, logic high configures Alternate Operation Mode.
Serial Bus Clock Input Serial Bus Data Bit Serial Bus Data Bit Serial Bus Enable Reset (SPI Registers and Logic) Optional Auxiliary ADC Serial Bus Data Out Bit AUX_SPI_clk Optional Auxiliary ADC Serial Bus Data Out Latch Clock AUX_SPI_csb Optional Auxiliary ADC Serial Bus Chip Select Bit AUX_ADC_A2 Auxiliary ADC A Input 2 AUX_ADC_B1 Auxiliary ADC B Input 1 AUX_ADC_B2 Auxiliary ADC B Input 2 AUX_ADC_REF Auxiliary ADC Reference
SCLK SDO SDIO SEN RESETB AUX_SPI_do
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AD9860/AD9862
DEFINITIONS OF SPECIFICATIONS Differential Nonlinearity Error (DNL, No Missing Codes) Aperture Delay
An ideal converter exhibits code transitions that are exactly 1 LSB apart. DNL is the deviation from this ideal value. Guaranteed no missing codes to 10-bit resolution indicate that all 1024 codes respectively, must be present over all operating ranges.
Integral Nonlinearity Error (INL)
The aperture delay is a measure of the Sample-and-Hold Amplifier (SHA) performance and specifies the time delay between the rising edge of the sampling clock input to when the input signal is held for conversion.
Aperture Uncertainty (Jitter)
Linearity error refers to the deviation of each individual code from a line drawn from "negative full scale" through "positive full scale." The point used as "negative full scale" occurs 1/2 LSB before the first code transition. "Positive full scale" is defined as a level 1 1/2 LSB beyond the last code transition. The deviation is measured from the middle of each particular code to the true straight line.
Phase Noise
Aperture jitter is the variation in aperture delay for successive samples and is manifested as noise on the input to the ADC.
Input Referred Noise
The rms output noise is measured using histogram techniques. The ADC output code's standard deviation is calculated in LSB and converted to an equivalent voltage. This results in a noise figure that can be referred directly to the input of the AD9860/ AD9862.
Signal-to-Noise and Distortion (S/N+D, SINAD) Ratio
Single-sideband phase noise power is specified relative to the carrier (dBc/Hz) at a given frequency offset (1 kHz) from the carrier. Phase noise can be measured directly in Single Tone Transmit Mode with a spectrum analyzer that supports noise marker measurements. It detects the relative power between the carrier and the offset (1 kHz) sideband noise and takes the resolution bandwidth (rbw) into account by subtracting 10 log(rbw). It also adds a correction factor that compensates for the implementation of the resolution bandwidth, log display, and detector characteristic.
Output Compliance Range
S/N+D is the ratio of the rms value of the measured input signal to the rms sum of all other spectral components below the Nyquist frequency, including harmonics but excluding dc. The value for S/N+D is expressed in decibels.
Effective Number of Bits (ENOB)
For a sine wave, SINAD can be expressed in terms of the number of bits. Using the following formula:
N=
(SINAD - 1.76 dB)
6.02
The range of allowable voltage at the output of a current-output DAC. Operation beyond the maximum compliance limits may cause either output stage saturation or breakdown, resulting in nonlinear performance.
Spurious-Free Dynamic Range (SFDR)
it is possible to get a measure of performance expressed as N, the effective number of bits. Thus, effective number of bits for a device for sine wave inputs at a given input frequency can be calculated directly from its measured SINAD.
Signal-to-Noise Ratio (SNR)
The difference, in dB, between the rms amplitude of the DAC's output signal (or ADC's input signal) and the peak spurious signal over the specified bandwidth (Nyquist bandwidth unless otherwise noted).
Pipeline Delay (Latency)
SNR is the ratio of the rms value of the measured input signal to the rms sum of all other spectral components below the Nyquist frequency, excluding harmonics and dc. The value for SNR is expressed in decibels.
Total Harmonic Distortion (THD)
The number of clock cycles between conversion initiation and the associated output data being made available.
Offset Error
First transition should occur for an analog value 1/2 LSB above -full scale. Offset error is defined as the deviation of the actual transition from that point.
Gain Error
THD is the ratio of the rms sum of the first six harmonic components to the rms value of the measured input signal and is expressed as a percentage or in decibels.
Power Supply Rejection
The first code transition should occur at an analog value 1/2 LSB above -full scale. The last transition should occur for an analog value 1 1/2 LSB below the nominal full scale. Gain error is the deviation of the actual difference between first and last code transitions and the ideal difference between first and last code transitions.
Power supply rejection specifies the converter's maximum full-scale change when the supplies are varied from nominal to minimum and maximum specified voltages.
Channel-to-Channel Isolation (Crosstalk)
In an ideal multichannel system, the signal in one channel will not influence the signal level of another channel. The channelto-channel isolation specification is a measure of the change that occurs to a grounded channel as a full-scale signal is applied to another channel.
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Typical Performance Characteristics-AD9860/AD9862
0 -10 -20
MAGNITUDE - dBm MAGNITUDE - dBm
0
fDATA = 32MSPS
4 INTERPOLATION
0
-10 -20
fDATA = 32MSPS
4 INTERPOLATION
-10 -20
fDATA = 32MSPS
4 INTERPOLATION
MAGNITUDE - dBm
-30 -40 -50 -60 -70 -80 -90
-30 -40 -50 -60 -70 -80 -90
-30 -40 -50 -60 -70 -80 -90
-100 0 20 40 60 80 100 110 120 140 FREQUENCY - MHz
-100 0 20 40 80 100 110 120 140 60 FREQUENCY - MHz
-100 0 20 40 80 100 110 120 140 60 FREQUENCY - MHz
TPC 1. AD9862 Tx Output 6 MHz Single Tone; CLKIN = 32 MHz; DLL 4 Setting
TPC 2. AD9862 Tx Output 6 MHz Single Tone; CLKIN = 64 MHz; DLL 2 Setting
TPC 3. AD9862 Tx Output 6 MHz Single Tone; CLKIN = 128 MHz; DLL 1 Setting
0
0
0
fDATA = 32MSPS
-20 1 INTERPOLATION
fDATA = 32MSPS
4 INTERPOLATION
MAGNITUDE - dBm
fDATA = 32MSPS
-20 4 INTERPOLATION
-20 MAGNITUDE - dBm -40
MAGNITUDE - dBm
-40
-40
-60
-60
-60
-80
-80
-80
-100 -120 0 20 40 60 80 100 110 120 140 FREQUENCY - MHz
-100 -120 0 20 40 60 80 100 110 120 140 FREQUENCY - MHz
-100 -120 7.90 7.92 7.94 7.96 7.98 8.00 8.02 8.04 8.06 8.08 FREQUENCY - MHz
TPC 4. TxDAC Generating an OFDM Signal; CLKIN = 64 MHz, DLL 2 Setting
TPC 5. TxDAC Generating an OFDM Signal; CLKIN = 64 MHz, DLL 2 Setting
TPC 6. Zoomed in Plot of Four Notched Carriers of OFDM Signal; CLKIN = 64 MHz, DLL 2 Setting
-60 -65 -70 THD 2nd 3rd
74
fDATA = 64MSPS
2 INTERPOLATION
fDATA = 64MSPS
73 2 INTERPOLATION
-50 -55 -60 -65
IMD - dBc
fDATA = 64MSPS
2 INTERPOLATION
AD9862
72
SNR - dB
THD - dBc
-75 -80 -85 -90 5 10 15 20 25 fOUT - MHz 30 35
71
-70 -75 -80
70
69
AD9860
-85 -90
AVDD = 3.0V AVDD = 3.3V AVDD = 3.6V 5 20 10 15 25 CARRIER FREQUENCY - MHz 30
68 0 5 10 15 20 FREQUENCY - MHz 25 30
-95
TPC 7. TxDAC Harmonic Distortion vs. fOUT
TPC 8. Signal-to-Noise Ratio (SNR) vs. fOUT
TPC 9. Two Tone Intermodulation vs. fOUT1 (fOUT2 = fOUT1 + 1 MHz)
REV. 0
-9-
AD9860/AD9862
0 -20 0 -20 0 -20
FFT MAGNITUDE - dBFS
FFT MAGNITUDE - dBFS
-40
FFT MAGNITUDE - dBFS
-40
-40
-60
-60
-60
-80
-80
-80
-100 -120 0 5 20 10 15 25 FFT OUTPUT - MHz 30
-100 -120 0 5 10 15 25 20 FFT OUTPUT - MHz 30
-100 -120 0 5 10 15 20 25 FFT OUTPUT - MHz 30
TPC 10. ADC Dual Tone FFT with Buffer Tones at 4.5 MHz and 5.5 MHz
TPC 11. ADC Dual Tone FFT without Buffer Tones at 4.5 MHz and 5.5 MHz
TPC 12. ADC Dual Tone FFT (undersampling) without Buffer Tones at 69.5 MHz and 70.5 MHz
68 66 64 62 60 58 56 54 52 50 0 50 100
BUFFERED 2V INPUT, 1 GAIN BUFFERED BYPASS 1V INPUT, 2 GAIN BUFFERED BYPASS 2V INPUT, 1 GAIN
11.0 10.5
70 68 66 64
LOW POWER MODE 1, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN BUFFER BYPASSED, 2V p-p, 1 RxPGA GAIN
70 68 66 64
SINAD - dBc
LOW POWER MODE 2, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN BUFFER BYPASSED, 2V p-p, 1 RxPGA GAIN LOW POWER MODE 2, BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
SINAD - dBc
10.0
62 60 58 56 54
LOW POWER MODE 1, BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
62 60 58 56 54
9.5
9.0
8.5
BUFFERED 1V INPUT, 2 GAIN
BUFFER ENABLED,
BUFFER ENABLED,
52 1V p-p INPUT,
8.0 250 300
52 1V p-p INPUT, 50
150 200 fIN - MHz 250 300
2 RxPGA GAIN
50 0
2
RxPGA GAIN
200 150 fIN - MHz
50
100
0
50
100
150
200
250
300
fIN - MHz
TPC 13. AD9862 Rx SINAD vs. fIN at 64 MSPS
TPC 14. AD9862 Rx SINAD vs. fIN at 32 MSPS
TPC 15. AD9862 Rx SINAD vs. fIN at 16 MSPS
62 60 58 56 54
BUFFERED BYPASS 1V INPUT, 2 GAIN
10.0 9.5
62 60 58
LOW POWER MODE 1, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN BUFFER BYPASSED, 2V p-p, 1 RxPGA GAIN
62 60 58 56
LOW POWER MODE 2, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN BUFFER BYPASSED, 2V p-p, 1 RxPGA GAIN
SINAD - dBc
9.0
56 54 52 50 48 LOW POWER MODE 1, BUFFER ENABLED, 46 1V p-p INPUT, 2 RxPGA GAIN 44 0 50 100 150
BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
SINAD - dBc
54 52 50 48 LOW POWER
MODE 2, BUFFER ENABLED, 46 1V p-p INPUT, 2 RxPGA GAIN BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
8.5 52 50 48 46 44 0 50 100 150 200 250 7.0 300
BUFFERED 1V INPUT, 2 GAIN BUFFERED 2V BUFFERED BYPASS INPUT, 1 GAIN 2V INPUT, 1 GAIN
8.0
7.5
44 200 250 300
0
50
100
150
200
250
300
fIN - MHz
fIN - MHz
fIN - MHz
TPC 16. AD9860 Rx SINAD vs. fIN at 64 MSPS
TPC 17. AD9860 Rx SINAD vs. fIN at 32 MSPS
TPC 18. AD9860 Rx SINAD vs. fIN at 16 MSPS
-10-
REV. 0
AD9860/AD9862
-50 -55 -60 -65
BUFFERED BYPASS 2V INPUT, 1 GAIN BUFFERED 2V INPUT, 1 GAIN
-50 AD9860 LOW POWER -55 ENABLED,
MODE 1, BUFFER 1V p-p INPUT,
-60 2 RxPGA GAIN
THD - dBc
AD9862 LOW POWER MODE 1, BUFFER ENABLED , 1V p-p INPUT, 2 RxPGA GAIN
-50 AD9860 LOW POWER -55 ENABLED,
MODE 2, BUFFER 1V p-p INPUT,
-60 2 RxPGA GAIN
THD - dBc
THD - dBc
-70 -75 -80 -85 -90 -95
BUFFERED 1V INPUT, 2 GAIN BUFFERED BYPASS 1V INPUT, 2 GAIN
-65 -70 -75 -80 -85 -90
AD9862 LOW POWER MODE 1, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN AD9860 LOW POWER MODE 1, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN
-65 -70 -75 -80 -85 -90
AD9862 LOW POWER MODE 2, BUFFER ENABLED , 1V p-p INPUT, 2 RxPGA GAIN
AD9860 LOW POWER MODE 2, BUFFER BYPASSED, 2Vp-p INPUT, 1 RxPGA GAIN AD9862 LOW POWER MODE 2, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN
-100 0 10 100 INPUT FREQUENCY - MHz 1000
0
50
100
150 200 fIN - MHz
250
300
0
50
100
150 200 fIN - MHz
250
300
TPC 19. Rx THD vs. fIN, FADC = 64 MSPS
TPC 20. Rx THD vs. fIN, FADC = 32 MSPS
TPC 21. Rx THD vs. fIN, FADC = 16 MSPS
-50 -55 -60 -65
BUFFERED BYPASS 1V INPUT, 2 GAIN BUFFERED BYPASS 2V INPUT, 1 GAIN
-50 -55 -60 -65
AD9862 LOW POWER MODE 1, BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
-50 -55 -60 -65 SFDR - dBc -70 -75 -80 -85
SFDR - dBc
-70 -75 -80 -85 -90 -95
SFDR - dBc
-70 -75 -80 -85
AD9860 LOW POWER MODE 1, AD9860 BUFFER BYPASSED, LOW POWER MODE 1, 2V p-p INPUT, BUFFER ENABLED, 1 RxPGA GAIN 1V p-p INPUT, 2 RxPGA GAIN
AD9860 LOW POWER MODE 2, BUFFER BYPASSED, 1V p-p INPUT, 2 RxPGA GAIN AD9860 LOW POWER MODE 2, BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
AD9862 LOW POWER MODE 2, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN AD9862 LOW POWER MODE 2, BUFFER ENABLED, 1V p-p INPUT, 2 RxPGA GAIN
BUFFERED 2V INPUT, 1 GAIN
BUFFERED 1V INPUT, 2 GAIN
-90 -95
AD9862 LOW POWER MODE 1, BUFFER BYPASSED, 2V p-p INPUT, 1 RxPGA GAIN
-90 -95
300
-100 0 10 100 INPUT FREQUENCY - MHz 1000
0
50
100
150
200
250
0
50
100
150
200
250
300
fIN - MHz
fIN - MHz
TPC 22. Rx SFDR @ 64 MSPS
TPC 23. Rx SFDR @ 32 MSPS
TPC 24. Rx SFDR @ 16 MSPS
1 0
280 270
800 700 NOMINAL
RELATIVE ATTENUATION - dB
Rx ANALOG POWER - mW
260
INPUT IMPEDANCE -
-1 -2 -3 -4 -5 -6 1 10 100 INPUT FREQUENCY - MHz 1000 NO BUFF 2V BUFF 1V 2 BUFF 2V 1 1
600 500 32MSPS LP MODE 400 300 16MSPS LP MODE 200 100 0
250 240 230 220 210 200 190 180 0 20 40 60 fIN - MHz 80 100
0
10
20
30
40
50
60
70
fADC - MSPS
TPC 25. Rx Input Attenuation
TPC 26. Rx Input Buffer Impedance vs. fIN
TPC 27. Rx Analog Power Consumption
REV. 0
-11-
AD9860/AD9862
REGISTER MAP (0x00-0x3F) 1
Register Name Address
General Rx Power Down Rx A Rx B Rx Misc Rx I/F Rx Digital RSV Tx Power Down RSV Tx A Offset Tx A Offset Tx B Offset Tx B Offset Tx A Gain Tx B Gain Tx PGA Gain Tx Misc Tx I/F Tx Digital Tx Modulator NCO Tuning Word NCO Tuning Word NCO Tuning Word DLL CLKOUT Aux ADC A2 Aux ADC A2 Aux ADC A1 Aux ADC A1 Aux ADC B2 Aux ADC B2 Aux ADC B1 Aux ADC B1 Aux ADC Control Aux ADC Clock Aux DAC A Aux DAC B Aux DAC C Aux DAC Update Aux DAC DAC Control SigDelt SigDelt ADC Low Power RSV 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 49, 50 44-62 63 Input Control ADC Div 2 Clock CLKOUT2 Divide Factor Inv2 Aux ADC A2 Data [1:0] Aux ADC A1 Data [1:0] Aux ADC A1 Data [9:2] Aux ADC B2 Data [1:0] Aux ADC B2 Data [9:2] Aux ADC B1 Data [1:0] Aux SPI SelBnot A Refsel B Aux ADC B1 Data [9:2] Select B Start B Aux DAC A Aux DAC B Aux DAC C Slave Enable Inv C Sigma-Delta Control Word [3:0] Sigma-Delta Control Word [11:4] Low Power Register for Rx Path Operation below 32 MSPS Reserved for Future Use Chip Rev ID Update C Update B Update A Power Down C Power Down B Power Down A Inv B Inv A Flag Refsel A Select A Start A CLK/4 Reserved
2
Bit 7
SDIO BiDir VREF (diff) Byp Buffer A Byp Buffer B
Bit 6
LSB First VREF
Bit 5
Soft Reset Rx Digital
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Purpose
SPI Setup
Rx Channel B Rx Channel A Buffer B Buffer A All Rx RxPGA A RxPGA B HS Duty Cycle Shared Ref Clk Duty Three State Rx Retime Twos Inv RxSync Mux Out Complement 2 Channel Keep -ve Hilbert Decimate Reserved for Future Use Alt Timing TxOff Enable Tx Digital Tx Analog Power Down [2:0] Mode Reserved for Future Use DAC A Offset [1:0] DAC A Offset Direction DAC A Offset [9:2] DAC B Offset [1:0] DAC B Offset Direction DAC B Offset [9:2] DAC A Coarse Gain DAC A Fine Gain DAC B Coarse Gain DAC B Fine Gain Tx PGA Gain Slave Enable Tx PGA Fast Tx Retime Q/I Order Inv TxSync Twos Inverse 2 Edges Interleaved Complement Sample 2 Data Paths Keep -ve Hilbert Interpolation Control Neg. Fine Tune Fine Mode Real Mix Neg. Coarse Tune Coarse Modulation FTW [7:0] FTW [15:8] FTW [23:16] DLL Multiplier Dis2 Aux ADC A2 Data [9:2] DLL Power Down Inv1 DLL FAST Dis1
Receive Path Setup
Transmit Path Setup
NCO Setup
Clock Setup
Auxiliary ADC Data and Setup
Auxiliary DAC Data and Setup
SigmaDelta Data and Setup Rx Low Power Reserved Chip ID
NOTES 1 When writing to a register with unassigned register bit(s), a logic low must be written to the unassigned bit(s). By default, after power up or RESET, all registers are set low, except for the bits in the shaded boxes, which are set high. 2 Decimal
-12-
REV. 0
AD9860/AD9862
REGISTER BIT DEFINITIONS REGISTER 0: GENERAL BIT 7: SDIO BiDir (Bidirectional)
high speed applications when clock duty cycle affects noise and distortion performance the most. This bit should be set high in conjunction with Clk Dut Enable register bit.
BIT 1: Shared Ref
Default setting is low, which indicates SPI serial port uses dedicated input and output lines (i.e., 4-wire interface), SDIO and SDO Pins, respectively. Setting this bit high configures the serial port to use the SDIO Pin as a bidirectional data pin.
BIT 6: LSB First
Default setting is low, which indicates MSB first SPI Port Access Mode. Setting this bit high configures the SPI port access to LSB first mode.
BIT 5: Soft Reset
Setting this bit high forces the dual receive ADCs into a mode to share their differential references to provide superior gain matching. When this option is enabled, the REFT of Channel A and Channel B should be connected together off-chip and the REFB of both channels should be connected.
BIT 0: Clk Duty
Writing a high to this register resets all the registers to their default values and forces the DLL to relock to the input clock. The Soft Reset Bit is a one shot register and is cleared immediately after the register write is completed.
REGISTER 1: Rx PWRDWN BIT 7: VREF, diff (Power-Down)
Setting this bit high enables an on-chip duty cycle stabilizer (DCS) circuit to generate the internal clock for the Rx block. This option is useful for adjusting for high speed input clocks with skewed duty cycle. The DCS Mode can be used with ADC sampling frequencies over 40 MHz.
REGISTER 5: Rx I/F (INTERFACE) BIT 4: Three-state
Setting this bit high will power down the ADC's differential references (i.e., REFT and REFB).
BIT 6: VREF (Power-Down)
Setting this bit high will force both Rx data output buses, including the RxSYNC Pin, into a three-state mode.
BIT 3: Rx Retime
Setting this register bit high will power down the ADC reference circuit (i.e., VREF).
BIT 5: Rx Digital (Power-Down)
Setting this bit high will power down the digital section of the receive path of the chip. Typically, any unused digital blocks are automatically powered down.
BIT 4/3: Rx Channel B/Rx Channel A (Power-Down)
The Rx path can use either of the clock outputs, CLKOUT1 or CLKOUT2, to latch the Rx output data. Since CLKOUT1 and CLKOUT2 have slight phase offsets, this provides some timing flexibility with the interface. By default, this bit is low and the Rx output latches use CLKOUT1. Setting this bit will force the Rx output latches to use CLKOUT2.
BIT 2: Twos Complement
Either ADC or both ADCs can be powered down by setting the appropriate register bit high. The entire Rx channel is powered down, including the differential references, input buffer, and the internal digital block. The bandgap reference remains active for quick recovery.
BIT 2/1: Buffer B/Buffer A (Power-Down)
Default data format for the Rx data is straight binary. Setting this bit high will generate two's complement data.
BIT 1: Inv RxSync
Setting either of these bits high will power down the input buffer circuits for the respective channel. The input buffer should be powered down when bypassed. By default, these bits are low and the input buffers are enabled.
BIT 0: All Rx (Power-Down)
When the receive data is multiplexed onto one data port (i.e., Mux Mode Enabled), the RxSYNC Pin can be used to decode which channel generated the current output data at the active port. Default condition is that RxSYNC is high when Channel A is at the output and is low when Channel B is at the output. Setting this bit high reverses this synchronization.
BIT 0: Mux Out
Setting this bit high powers down all circuits related to the receive path.
REGISTER 2/3: Rx A/Rx B BIT 7: Bypass Buffer A/Bypass Buffer B
Setting this bit high enables the Rx Mux Mode. Default setting is low, which is Dual Port Mode, (i.e., non Rx Mux Mode). When in Rx Mux Mode, both Rx channels share the same output data bus, pins D0A to D9A (for AD9860) or D0A to D11A (for AD9862). The other Rx output bus (pins D0B to D9B or D0B to D11B) outputs a low logic.
REGISTER 6: Rx Digital BIT 3: 2 Channel
Setting either of these bits high will bypass the respective input buffer circuit. When the buffer is bypassed, the input signal is routed directly to the switched capacitor SHA input of the RxPGA. When operating with buffer bypassed, it should be powered down.
BIT 0-4: RxPGA A/RxPGA B
Setting this bit low disables the Rx B output data port (pins D0B to D9B or D11B), forcing the output pins to zero. By default, the bit is high and both data paths are active.
BIT 2: Keep -ve
These 5-bit straight binary registers (Bit 0 is the LSB, Bit 4 is the MSB) provide control for the programmable gain amplifiers in the dual receive paths. A 0 dB to 20 dB gain range is accomplished through a switched capacitor network with fast settling of a few clock cycles. The step size is approximately 1 dB. The register default setting is minimum gain or hex00. The maximum setting for these registers is hex14.
REGISTER 4: Rx MISC BIT 2: HS (High Speed) Duty Cycle
This bit selects whether the receive Hilbert filter will filter positive or negative frequencies, assuming the filter is enabled. By default this bit is low, which passes positive frequencies. Setting this bit high will configure the filter to pass negative frequencies.
BIT 1: Hilbert
This bit enables or disables the Hilbert filter in the receive path. By default, this bit is low, which disables the receive Hilbert filter. Setting this bit high enables the receive Hilbert filter.
BIT 0: Decimate
Setting this bit high optimizes duty cycle of the internal ADC sampling clock. It is recommended that this bit be set high in REV. 0
This register enables or disables the decimation filters. By default, the register setting is low and the decimation filter is disabled. -13-
AD9860/AD9862
Setting this bit high enables the decimation filters and decimates the receive data by two.
REGISTER 8: Tx PWRDWN BIT 5: Alt Timing Mode DAC A/DAC B Offset Direction
The timing section in the data sheet describes two timing modes, the "Normal Operation" and the "Alternate Operation" modes. At power up, the default configuration is established from the logic level of the Mode/TxBlank pin. If Mode/TxBlank is logic low, the Normal Operation mode is the default; if the Mode/ TxBlank pin is held at a logic high, the Alternative Operation mode is configured at power-up (the DLL is forced to multiply by 4 at power-up by default in this mode). After power up, the operation mode can be configured so that the Mode/TxBlank pin can be used for other functions. To allow this, set this bit high.
BIT 4: TxOff Enable
This bit determines to which of the differential output pins for the selected channel the offset current will be applied. Setting this bit low will apply the offset to the negative differential pin. Setting this bit high will apply the offset to the positive differential pin.
REGISTER 14/15: DAC GAIN A/B BIT 6, 7: DAC A/DAC B Coarse Gain Control
These register bits will scale the full-scale output current (IOUTFS) of either Tx channel independently. IOUT of the Tx channels is a function of the RSET resistor, the TxPGA setting, and the Coarse Gain Control setting. MSB, LSB 10 or 11 01 00 Tx Channel Current Scaling Does not scale output current Scales output current by 1/2 Scales output current by 1/11
By default, the Mode/TxBlank pin is not used for any transmit synchronization. The Mode/TxBlank pin input can be used to serve two functions, blanking the DAC outputs and slaving the TxPGA gain control. When this bit is set high, a logic high on the Mode/TxBlank pin forces the Tx digital block to stop clocking. In this mode, the Tx outputs will be static, holding their last update values. To slave the TxPGA gain control to the Mode/TxBlank pin input, register Slave Enable (Register 17, Bit 1) needs to also be programmed. See that register for more information.
BIT 3: Tx Digital (Power-Down)
BIT 5-0: DAC A/DAC B Fine Gain
The DAC output curve can be adjusted fractionally through the Gain Trim Control. Gain trim of up to 4% can be achieved on each channel individually. The Gain Trim register bits are a twos complement attention control word. MSB, LSB 100000 111111 000000 000001 011111 Maximum positive gain adjustment Minimum positive gain adjustment No adjustment (default) Minimum negative gain adjustment Maximum negative gain adjustment
By default this bit is low, enabling the transmit path digital to operate as programmed through other registers. By setting this bit high, the digital blocks are not clocked to reduce power consumption. When enabled, the Tx outputs will be static, holding their last update values.
BIT 0-2: Tx Analog (Power-Down)
REGISTER 16: TxPGA GAIN BIT 0-7: TxPGA Gain
Three options are available to reduce analog power consumption for the Tx channels. The first two options disable the analog output from Tx channel A or B independently, and the third option disables the output of both channels and reduces the power consumption of some of the additional analog support circuitry for maximum power savings. With all three options, the DAC bias current is not powered down so recovery times are fast (typically a few clock cycles). The list below explains the different modes and settings used to configure them. Tx Analog Power-Down Bits Setting [2:0]
This 8 bit, straight binary (Bit 0 is the LSB, Bit 7 is the MSB) register controls for the Tx programmable gain amplifier (TxPGA). The TxPGA provides a 20 dB continuous gain range with 0.1 dB steps (linear in dB) simultaneously to both Tx channels. By default, this register setting is hex00. MSB, LSB 000000 111111 Minimum gain scaling -20 dB Maximum gain scaling 0 dB
REGISTER 17: Tx MISC BIT 1: Slave Enable
Power-Down Option
Power-Down Tx B Channel Analog Output [1 0 0] Power-Down Tx A Channel Analog Output [0 1 0] Power-Down Tx A and Tx B Analog Outputs [1 1 1]
REGISTER 10/11/12/13: DAC OFFSET A/B DAC A/DAC B Offset
The TxPGA Gain is controlled through register TxPGA Gain setting and by default is updated immediately after the register write. If this bit is set, the TxPGA Gain update is synchronized with the rising edge of a signal applied to the Mode/TxBlank pin. Setting TxOff enable in Register 8 is also required.
BIT 0: TxPGA Fast (Update Mode)
These 10-bit, twos complement registers control a dc current offset that is combined with the Tx A or Tx B output signal. An offset current of up to 12% IOUTFS (2.4 mA for a 20 mA fullscale output) can be applied to either differential pin on each channel. The offset current can be used to compensate for offsets that are present in an external mixer stage, reducing LO leakage at its output. Default setting is hex00, no offset current. The offset current magnitude is set using the lower nine bits. Setting the MSB high will add the offset current to the selected differential pin, while an MSB low setting will subtract the offset value.
The TxPGA Fast bit controls the update speed of the TxPGA. When Fast Update mode is enabled, the TxPGA provides fast gain settling within a few clock cycles. Default setting for this bit is low, which indicates Normal Update mode. Fast mode is enabled when this bit is set high.
REGISTER 18: Tx IF (INTERFACE) BIT 6: Tx Retime
The Tx path can use either of the clock outputs, CLKOUT1 or CLKOUT2, to latch the Tx input data. Since CLKOUT1 and CLKOUT2 have slight phase offsets, this provides some timing flexibility with the interface. By default, this bit is high and the Tx input latches use CLKOUT1. Setting this bit low will force the Tx latches to use CLKOUT2.
-14-
REV. 0
AD9860/AD9862
BIT 5: Q/I Order BIT 3: Real Mix Mode
This register indicates the order of received complex transmit data. By default this bit is low, representing I data preceding Q data. Alternatively, if this bit is set high, the data format is defined as Q data preceding I data.
BIT 4: Inv TxSync
This register identifies how the first and second data sets are identified in a complex data set using the TxSYNC bit. By default this bit is low, and TxSYNC low indicates the first data set is at the Tx port; TxSYNC high indicates the second data set is at the Tx port. Setting this bit high inverts the TxSYNC bit. TxSYNC high indicates the first of the data set, and TxSYNC low indicates the second of the data set.
BIT 3: Twos Complement
This bit determines if the coarse modulation (controlled by register Coarse Modulation, will perform a separate real mix on each channel or a complex mix using the dual channel data. By default, this bit is set low and a complex mix will be performed. Setting this bit high will enable the Real Mix mode. Note, the Fine Modulator Block only performs complex mixing.
BIT 2: Negative Coarse Tune
When this bit is low (default), the coarse modulator provides positive shifts in frequency. Setting this bit high will shift the coarse modulator processed data negative in frequency.
BIT 1,0: Coarse Modulation
The default data format for Tx data is straight binary. Set this bit high when providing twos complement Tx data.
BIT 2: Inverse Sample
These bits control what coarse modulation processing will be performed on the transmit data. A setting of binary 00 (default) will bypass the modulation block, a setting of binary 01 will shift the transmit data by fDAC/4, and a setting of binary 10 will shift the transmit data by fDAC/8.
REGISTER 21/22/23: NCO TUNING WORD FTW [23:0]
By default, the transmit data is sampled on the rising edge of the CLKOUT. Setting this bit high will change this, and the transmit data will be sampled on the falling edge.
BIT 1: 2 Edges
If the CLKOUT rate is running at half the interleaved data rate, both edges of the CLKOUT must latch transmit data. Setting this bit high allows this clocking configuration.
BIT 0: Interleaved
These three registers set the 24-bit frequency tuning word (FTW) for the NCO in the fine modulator stage of the Tx path. The NCO full-scale tuning word is straight binary and produces a frequency equivalent to fDAC/4 with a resolution of fDAC/226.
REGISTER 24: DLL BIT 6: Input Clock Control
By default, the AD9860/AD9862 powers up in single DAC operation. If dual transmit data is to be used, the interleaved data option needs to be enabled by setting this bit high.
REGISTER 19: Tx DIGITAL BIT 4: 2 Data Paths
Setting this bit high enables both transmit digital paths. By default, this bit is low and the transmit path utilizes only a single channel.
BIT 3: Keep -ve
This bit defines what type of clock will be driving the AD9860/ AD9862. The default state is low, which allows either crystal connected to OSC1 and OSC2 or single-ended reference clock driving OSC1 to drive the internal timing circuits. If a crystal will not be used, the internal oscillator should be disabled after power-up by setting this bit high.
BIT 5: ADC Div2
This bit configures the Tx Hilbert filter for either positive or negative frequencies pass band, assuming it is enabled. By default this bit is low, which selects the positive frequencies. Setting this bit high will setup the Hilbert filter to pass negative frequencies.
BIT 2: Hilbert
By default, the ADC is driven directly by the input clock in Normal Timing Operation mode or the DLL output in the Alternative Timing Operation mode. Setting this bit high will clock the ADC at one half the previous clock rate. This is described further in the timing section.
BIT 4,3: DLL Multiplier
This bit enables or disables the Hilbert filter in the transmit path. By default, this bit is low, which disables the transmit Hilbert filter. Setting this bit high enables the transmit Hilbert filter.
BIT 1,0: Interpolation Control
These register bits control the interpolation rate of the transmit path. Default settings are both bits low, indicating that both interpolation filters are bypassed. The MSB and LSB are address D19, Bits 1 and 0, respectively. Setting binary 01 provides an interpolation rate of 2 ; binary 10 provides an interpolation rate of 4 .
REGISTER 20: Tx MODULATOR BIT 5: Negative Fine Tune
These bits control the DLL multiplication factor. A setting of binary 00 will bypass the DLL, a setting of binary 01 will multiply the input clock by 2, and a setting of binary 10 will multiply the input clock by 4. Default mode is defined by Mode/TxBlank logic level at power-up or RESET, which configures either Normal Operation Timing mode or Alternative Timing mode. In Alternative Timing mode, the DLL will lock to 4 multiplication factor (the DLL FAST register remains low by default). If the Mode/TxBlank pin is low, by default the DLL will be bypassed and a 1 clock is used internally.
BIT 2: DLL Power-Down
When this bit is low (default), the Numerically Controlled Oscillator (NCO) provides positive shifts in frequency, assuming fine modulation is enabled. Setting this bit high will use a negative frequency shift in the Fine Complex Modulator.
BIT 4: Fine Mode
Setting this register bit high forces the CLK IN multiplier to a power-down state. This mode can be used to conserve power or to bypass the internal DLL. To operate the AD9860/AD9862 when the DLL is bypassed, an external clock equal to the fastest on-chip clock is supplied to the OSC pin(s).
BIT 0: DLL FAST
By default, the NCO and fine modulation stage are bypassed. Setting this bit high will enable the use of the digital complex modulator, enabling tuning with the NCO.
The DLL can be used to generate output frequencies between 32 MHz to 128 MHz. Because of the large range of locking frequencies allowed, the DLL is separated into two output frequency ranges, a "slow" range between 32 MHz to 64 MHz and a "fast" range starting at frequencies above 64 MHz to 128 MHz. By -15-
REV. 0
AD9860/AD9862
default, this bit is low, setting up the DLL in "slow" mode. This bit must be set high for DLL output frequencies over 64 MHz.
REGISTER 25: CLKOUT BIT 7, 6: CLKOUT2 Divide Factor
the Auxiliary ADCs with a clock that is 1/4 of the receive ADC conversion rate. The conversion rate of the auxiliary ADCs should be less than 20 MHz.
REGISTER 36, 37, 38: AUX DAC A/B/C Auxiliary DAC A, B, and C Output Control Word
These bits control what rate the CLKOUT2 Pin will operate at relative to the DLL output rate. The DLL output rate can be output directly or divided by 2, 4, or 8. Bit 7 is the MSB and Bit 6 is the LSB. MSB, LSB 00 (Default) 01 10 11
BIT 5, 1: Inv 2/Inv 1
Relative CLKOUT2 Frequency Equals DLL output rate Equals DLL output rate divided by 2 Equals DLL output rate divided by 4 Equals DLL output rate divided by 8
Three 8-bit, straight binary words are used to control the output of three on-chip auxiliary DACs. The auxiliary DAC output changes take effect immediately after any of the serial write is completed. The DAC output control words have default values of 0. The smaller programmed output controlled words correspond to lower DAC output levels.
REGISTER 39: AUX DAC UPDATE BIT 7: Slave Enable
The output clocks from CLKOUT1 and CLKOUT2 can be inverted by setting the appropriate one of these bits high.
BIT 4, 0: Dis 2/Dis 1
A low setting (default) updates the auxiliary DACs after the respective register is written to. To synchronize the auxiliary DAC outputs to each other, a slave mode can be enabled by setting this bit high and then setting a high to the appropriate update registers.
BIT 2/1/0: Update C, B, and A
The output clocks from CLKOUT1 and CLKOUT2 can be disabled and a logic low output is forced by setting the appropriate one of these bits high.
REGISTER 26-33: AUXILIARY ADC A2/A1/B2/B1 AUX ADC A2, A1, B2, B1 Data
These registers are read only registers that are used for read back of the 10-bit auxiliary ADC. The 10 bits are broken into a two registers, one containing the upper eight bits and the other containing the lower two bits.
REGISTER 34: AUX ADC CONTROL BIT 7: Aux SPI (Enable)
Setting a high bit to any of these registers initiates an update of the respective Auxiliary DAC, A, B, or C, when Slave mode is enabled using the Slave Enable register. The register bit is a one shot and always reads back a low. Note: be sure to keep the Slave Enable bit high when using the auxiliary DAC synchronization option.
REGISTER 40: AUX DAC POWER-DOWN BIT 2/1/0: Power Down C, B, and A
Setting any of these bits high will power down the appropriate auxiliary DAC. By default, these bits are low and the auxiliary DACs are enabled.
REGISTER 41: AUX DAC CONTROL BIT 4, 2, 0: Inv C, B, and A
One of the Auxiliary ADCs can be controlled through an dedicated Auxiliary Serial Port. Setting this bit high enables this mode.
BIT 6: Sel BnotA
If the auxiliary Serial port is used, this bit selects which Auxiliary ADC, A or B, will be using the dedicated Auxiliary Serial port. The Auxiliary Serial port by default (low setting) controls Auxiliary ADC A. Setting this bit high will allow the Auxiliary Serial Port to control Auxiliary ADC B.
BIT 5, 2: Refsel B/A
Setting any of these bits high will invert the appropriate Auxiliary DAC control word setting. By default, these bits are low and the output control word is decoded as noninverted, straight binary.
REGISTER 42/43: SIGDELT (SIGMA-DELTA) Sigma-Delta Output Control Word
By default, the auxiliary ADCs use an external reference applied to the AUX_REF pin. This voltage will act as the full-scale reference for the selected auxiliary ADC. Either auxiliary ADC can use an internally generated reference, which is a buffered version of the analog supply voltage. To enable use of the internal reference for either of the auxiliary ADCs, the respective Refsel register should be set high.
BIT 4, 1: Select B/A
A 12-bit straight binary word is used to control the output of an on-chip sigma-delta converter. The sigma-delta output changes take effect immediately after any serial write is completed. The sigma-delta output control words have default values of 0. The smaller programmed output controlled words correspond to lower integrated sigma-delta output levels.
REGISTER 49,50 : RX LOW POWER MODE
These bits select which of the two inputs will be connected to the respective auxiliary ADC. By default (setting low), the AUX_ADC_A2 pin is connected to Auxiliary ADC A and AUX_ADC_B2 pin is connected to Auxiliary ADC B. Setting the respective bit high will connect the AUX_ADC_A1 pin to Auxiliary ADC A and/or AUX_ADC_B1 pin to Auxiliary ADC B.
BIT 3, 0: Start B/A
Setting these bits will scale down the bias current to the ADC analog block when the device is operated at lower speeds. By default, these bits are low and the bias is at a nominal setting. For ADC operation at or below 32 MSPS, Register 49 can be set to 0x03 and Register 50 can be set to 0xEC; this will reduce Rx AVDD power consumption by about 30% relative to nominal. For ADC operation at or below 16 MSPS, Register 49 can be set to 0x03 and Register 50 can be set to 0x9E; this will reduce Rx AVDD power consumption by about 60% relative to nominal.
REGISTER 63: CHIP ID BIT 7-0: Rev ID
Setting a high bit to either of these registers initiates a conversion of the respective auxiliary ADC, A or B. The register bit always reads back a low.
REGISTER 35: AUX ADC CLOCK BIT 0: CLK/4
This read only register indicates the revision of the AD9860/AD9862.
Reserved Registers
Reserved registers are held for future development and should By default (setting low), the auxiliary ADCs are run at the receive never be written to. ADC conversion rate divided by 2. Setting this bit high will run -16- REV. 0
AD9860/AD9862
Blank Registers
Blank registers, i.e., the registers with 0 settings and no indicated function, are placeholders used throughout the register map for spacing the AD9860/AD9862 control bits in a logic fashion and, potentially can be used for future development. A low should always be written to these registers if a write needs to take place.
SERIAL PORT INTERFACE
SDO is a serial output pin used for read back operations in 4-wire mode and is three-stated when SDIO is configured for bidirectional operation.
Instruction Header
The Serial Port Interface (SPI) is used to write to and read from the AD9860/AD9862 internal programmable registers. The serial interface uses four pins: SEN, SCLK, SDIO, and SDO by default. SEN is a serial port enable pin, SCLK is the serial clock pin, SDIO is a bidirectional data line and SDO is a serial output pin. SEN is an active low control gating read and write cycles. When SEN is high, SDO and SDIO are three-stated. SCLK is used to synchronize SPI read and writes at a maximum bit rate of 16 MHz. Input data is registered on the rising edge and output data transitions on the falling edge. During write operations, the registers are updated after the 16th rising clock edge (and 24th rising clock edge for the dual byte case). Incomplete write operations are ignored. SDIO is an input only by default. Optionally, a 3-pin interface may be configured using the SDIO for both input and output operations and three-stating the SDO pin (see SDIO BiDir register).
tDH tDS
SEN
Each SPI read or write consists of an instruction header and data. The instruction header is made up of an 8-bit word and is used to set up the register data transfer. The 8-bit word consists of a read/not write bit, R/nW (the MSB), followed by a double/ not single bit (2/n1) and the 6-bit register address.
Write Operations
The SPI write operation uses the instruction header to configure a one or two register write using the 2/n1 bit. The instruction byte followed by the register data, is written serially into the device through the SDIO pin on rising edges of the interface clock at SCLK. The data can be transferred MSB first or LSB first depending on the setting of the LSB First register. Figure 1 includes a few examples of writing data into the device. Figure 1a shows a write using 1 Byte and MSB First mode set; Figure 1b shows an MSB first, 2 Byte write; and Figure 1c shows an LSB first, 2 Byte write. Note the differences between LSB and MSB First modes: instruction header and data are reversed, and in 2 Byte writes, the first data byte is written to the address in the header, N and the second data byte is written to the n-1 address. In LSB First mode, the first data byte is still written to the address in the instruction header, but the second data byte is written to the N+1 address.
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Figure 1. SPI Write Examples a. (top) 1 Byte, MSB First Mode; b. (middle) 2 Byte, MSB First Mode; c. (bottom) 2 Byte, LSB First Mode -17-
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INSTRUCTION HEADER SDO DON'T CARE D0 D1 D2 D3 D4 D5 D6 D7 DON'T CARE
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Figure 2. SPI Read Examples a. (top) 4-Wire Interface, MSB first; b. (middle) 3-Wire Interface, MSB first; c. (bottom) 4-Wire Interface, LSB first
Read Operation
The read back of registers is a single data byte operation. The readback can be configured to use three pins or four pins and can be formatted as MSB first or LSB first. The instruction header is written to the device either MSB or LSB first (depending on the mode) followed by the 8-bit output data (appropriately MSB or LSB justified). By default, the output data is sent to the dedicated output pin (SDO). 3-wire operation can be configured by setting the SDIO BiDir register. In 3-wire mode, the SDIO pin will become an output pin after receiving the 8-bit instruction header with a read back request. Figure 2a shows an MSB first, 4-pin SPI read; Figure 2b shows an MSB first, 3-pin read; and Figure 2c shows an LSB first, 4-pin read.
SYSTEM BLOCK DESCRIPTION
features include two auxiliary ADCs, a programmable sigma-delta output, three auxiliary DACs, integrated clock circuitry to generate all internal clocks, and buffered output clocks from a single input reference. The AD9860/AD9862 system functionality is described in the following four sections: the Transmit Block, Receive Block, Timing Generation Block, and the Auxiliary Function Block. The following sections provide a brief description of the blocks and applications for the four sections.
TRANSMIT SECTION COMPONENTS
The AD9860/AD9862 integrates transmit and receive paths with digital signal processing blocks and auxiliary features. The auxiliary
The transmit block (Tx) accepts and can process real or complex data. The Tx interface is configurable for a variety of data formats and has special processing options such as interpolation and Hilbert filters. A detailed block diagram of the AD9860/AD9862 transmit path is shown in Figure 3. The transmit block diagram is broken into these stages: DAC (Block A), Coarse Modulation (Block B), REV. 0
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BLOCK A BLOCK B BYPASSABLE DIGITAL QUADRATURE MIXER BLOCK C BYPASSABLE LOW-PASS INTERPOLATION FILTER BLOCK D BYPASSABLE DIGITAL QUADRATURE MIXER BLOCK E HILBERT FILTER DAC
IOUT+A IOUT-A IOUT+B PGA IOUT-B TxDAC PGA TxDAC I HILBERT FILTER Q TxDATA [0:13]
fS/4, fS/8
DDS
Figure 3. Transmit Section Block Diagram
Interpolation Stage (Block C), Fine Modulation Stage (Block D), Hilbert filter (Block E), and the Latch/Demultiplexing circuitry.
DAC
The DAC stage of the AD9860/AD9862 integrates a high performance TxDAC core, a programmable gain control through a Programmable Gain Amplifier (TxPGA), coarse gain control, and offset adjustment and fine gain control to compensate for system mismatches. The TxDAC core of the AD9860/AD9862 provides dual, differential, complementary current outputs generated from the 12-/14-bit data. The 12-/14-bit Dual DACs support update rates up to 128 MSPS. The differential outputs (i.e., IOUT+ and IOUT-) of each dual DAC are complementary, meaning they always sum to the full-scale current output of the DAC, IOUTFS. Optimum ac performance is achieved with the differential current interface drives balanced loads or a transformer. The maximum full-scale output current, IOUTFSMAX, is set by the external resistor (RSET), which sets the DAC reference current. The RSET resistor is connected between the FSADJ Pin to ground. The relationship between IOUTFSMAX and RSET is:
E 1.23 V IOUTFSMAX ~ 67 A E RSET
Fine Gain controls and dc offset controls can be used to compensate for mismatches (for system level calibration), allowing improved matching characteristics of the two Tx channels and aiding in suppressing LO feedthrough. This is especially useful in image rejection architectures. The 10-bit dc offset control of each DAC can be used independently to provide a 12% IOUTFSMAX of offset to either differential pin, thus allowing calibration of any system offsets. The fine gain control with 5-bit resolution allows the IOUTFSMAX of each DAC to be varied over a 4% range, thus allowing compensation of any DAC or system gain mismatches. Fine gain control is set through the DAC A/B Fine Gain registers and the offset control of each DAC is accomplished using DAC A/B Offset registers. A power-down option allows the user to power down the analog supply current to both DACs or either DAC, individually. A digital power-down is also possible through either the Tx PwrDwn register or the Mode/TxBlank pin.
Coarse Modulator
Typically, RSET is 4 kW, which sets IOUTFSMAX to 20 mA, the optimal dynamic setting for the TxDACs. Increasing RSET by a factor of 2 will proportionally decrease IOUTFSMAX by a factor of 2. IOUTFSMAX of each DAC can be re-scaled either simultaneously with the TxPGA Gain register or independently with DAC A/B Coarse Gain registers. The TxPGA function provides 20 dB of simultaneous gain range for both DACs and is controlled by writing to SPI register TxPGA Gain for a programmable full-scale output of 10% to 100% IOUTFSMAX. The gain curve is linear in dB, with steps of about 0.1 dB. Internally, the gain is controlled by changing the main DAC bias currents with an internal TxPGA DAC whose output is heavily filtered via an on-chip R-C filter to provide continuous gain transitions. Note, the settling time and bandwidth of the TxPGA DAC can be improved by a factor of 2 by writing to the TxPGA Fast register. Each DAC has independent coarse gain control. Coarse gain control can be used to accommodate different IOUTFS from the dual DACs. The coarse full-scale output control can be adjusted using the DAC A/B Coarse Gain registers to 1/2 or 1/11th of the nominal full scale current. REV. 0
A digital coarse modulator is available in the transmit path to shift the spectrum of the input data by fDAC/4 or fDAC/8. If the input data consists of complex data, the modulator can be configured to perform a complex modulation of the input spectrum. If the data in the transmit path is not complex, a real mix can be performed separately on each channel thereby frequency shifting the real data and images by fDAC/4 or fDAC/8. Real or complex mixing is configured by setting the Real Mix register. By default, the coarse modulator is bypassed. It can be configured using Coarse Modulation and Neg Coarse Tune registers.
Interpolation Stage
Interpolation filters are available for use in the AD9860/AD9862 transmit path, providing 1 (bypassed), 2 , or 4 interpolation. The interpolation filters effectively increase the Tx data rate while suppressing the original images. The interpolation filters digitally shift the worst case image further away from the desired signal, thus reducing the requirements on the analog output reconstruction filter. There are two 2 interpolation filters available in the Tx path. An interpolation rate of 4 is achieved using both interpolation filters; an interpolation rate of 2 is achieved by enabling only the first 2 interpolation filter. The first interpolation filter provides 2 interpolation using a 39 tap filter. It suppresses out-of-band signals by 60 dB or more and has a flat passband response (less than 0.1 dB ripple) extending to 38% of the AD9860/AD9862 input Tx data rate (19% of the DAC update rate, fDAC). The maximum input data rate is 64 MSPS per channel when using 2 interpolation.
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The second interpolation filter will provide an additional 2 interpolation for an overall 4 interpolation. The second filter is a 15 tap filter. It suppresses out-of-band signals by 60 dB or more. The flat passband response (less than 0.1 dB attenuation) is 38% of the Tx input data rate (9.5% of fDAC). The maximum input data rate per channel is 32 MSPS per channel when using 4 interpolation. The 2 and 4 Interpolation Filter Transfer function plots are shown in Figure 4a and 4b, respectively.
10 0 -10
80
Hilbert Filter
The Hilbert filter is available to provide a Hilbert transform of "real" input data at a low intermediate frequency (IF) between 12.5% to 38% of the input data rate. The Hilbert filter essentially transforms this "real," single channel input data into a complex representation (i.e., I and Q components) that can be used as part of an image rejection architecture. The complex data can than be processed further using the on-chip digital complex modulators. The Hilbert filter requires 4 interpolation to be enabled and accepts data at a maximum 32 MSPS. Figure 5 shows a spectral plot of the Hilbert filter impulse response.
100
INTERPOLATION FILTER
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Figure 5. Tx Hilbert Filter, Keeping Positive Frequencies Spectral Plot
Latch/Demultiplexer
-30 -40 -50 -60 -70 -80 -90 -100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 NORMALIZED - fS INCLUDUNG SIN (X)/X
The AD9860/AD9862 Tx path accepts dual or single channel data. The dual channel data can represent two independent real signals or a complex signal. Various input data latching schemes relative to one of the output clocks, CLKOUT1 or CLKOUT2, are allowed, including using any combination of rising and falling clock edges. Associated Tx timing is discussed in detail in the Clock Overview section of the data sheet.
TRANSMIT APPLICATIONS SECTION
MAGNITUDE - dB
Figure 4. Spectral Response of 2 Interpolation Filter (top) and 4 Interpolation Filter (bottom)
Fine Modulation Stage
A digital fine modulation stage is available in the transmit path to shift the complex Tx output spectrum using a 24-bit numerically controlled oscillator (NCO). To utilize the Fine Modulation Block, 4 interpolation is required. Therefore, the maximum input date rate is 32 MSPS per channel, which generates a DAC update rate, fDAC, of 128 MSPS. The NCO can tune up to 1/4 of fDAC, providing a step resolution of fDAC/226. Since the Fine Modulation Stage precedes the Interpolation Filters, care must be taken to ensure the entire desired signal is placed within the pass band of the Interpolation Filter. By default, the Fine Modulation Block is bypassed. To enable it to perform a complex mix of the Tx I and Q data, Register 2's data paths, Fine Mod and Fine, should be configured. The NCO frequency tuning word is set in the three FTW registers.
The AD9860/AD9862 transmit path (Tx) includes two, high speed, high performance, 12-/14-bit TxDACs. Figure 3 shows a detailed block diagram of the transmit data path and can be referred to throughout the explanation of the various modes of operation. The various Tx modes of operation are broken into three parts, determined by the format of the input data. They are: 1. Single Channel DAC Data 2. Two Independent Real Signal DAC Data (diversity or dual channel 3. Dual Channel Complex DAC Data (I and Q or Single Sideband)
Single Channel DAC Data
In this mode, 12-/14-bit single channel Tx data is provided to the AD9860/AD9862 and latched using either CLKOUT1 or CLKOUT2 edges as defined in the Clock Overview section of the data sheet. All Tx digital signal processing blocks can be utilized to address reconstruction filtering at the DAC output and aid in frequency tuning.
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In most systems, the DAC (and each up-converter stage) requires analog filtering to meet spectral mask and out-of-band spurious emissions requirements. Digital interpolation (Block C) and Hilbert filtering (Block E) can be used to relax some of the system analog filtering. Digital 2 interpolation with input data rates of up to 64 MSPS or 4 interpolation with input data rates of 32 MSPS is available in this mode (or interpolation filters can be bypassed to achieve a 128 MSPS input data rate). The data bandwidth with 2 or 4 interpolation enabled is up to 38% of the input data rate. If no interpolation is enabled, the data bandwidth will be the full Nyquist band with Sinc limitations. The interpolation filters are configured through the Interpolation Serial register. The Hilbert filter can be enabled in this mode to suppress the positive or negative image that naturally occurs with real data. The single sideband signal when combined with a quadrature modulator can upconvert the desired signal and suppressed image, forming a Hartley Image Rejection Architecture (both Tx paths need to be enabled to produce the Image Rejection Architecture). The Hilbert filter will provide over 50 dB image suppression for signals between 12.5% to 38% of the input data rate. The Hilbert filter can be enabled and configured using the Hilbert and Keep -ve Serial registers. Digital frequency tuning the Tx output is also possible in this mode using the coarse modulation block. The coarse modulation block can be used to frequency shift the Tx signal either -fDAC/4, -fDAC/8, +fDAC/8 or +fDAC/4. The coarse modulator does not require the Hilbert filter to be enabled, in which case the real signal and image will shift. If the Hilbert filter is enabled, a complex mix can be performed on the single sideband signal by the coarse modulator (Note: the Hilbert filter does not need to be enabled if single sideband data is provided externally). The fine modulator can be used to accurately place the output signal shifting the Tx data spectrum in the positive or negative direction with a resolution of fDAC/226. The fine modulator requires both 4 interpolation and the Hilbert filter enabled to be used in this mode. The coarse modulator and fine modulator can both be used and provide a tuning range between 68% of the DAC Nyquist frequency. If all Tx DSP blocks are bypassed, the AD9860/AD9862 operates similar to a standard TxDAC. In Single Channel DAC Data mode, only the Channel A DAC is used; Channel B is powered down to reduce power consumption.
Two Independent Real Signal DAC Data
independently. The Tx digital processing blocks available in this mode are the Interpolation Filters (Block C) and the Coarse Modulator (Block D). As mentioned previously, the interpolation filters can be used to relax requirements on the external analog filters. The maximum rate of the Tx interface is 128 MSPS, i.e., 64 MSPS/channel with interleaved data. Therefore to fully take advantage of the DACs maximum update rate of 128 MSPS, 2 interpolation is required. The 4 interpolation filter is recommended for input data rates equal to or less than 32 MSPS/channel (64 MSPS interleaved). The data bandwidth with 2 or 4 interpolation enabled is up to 37.5% of the channel input data rate. If no interpolation is enabled, the data bandwidth will be the full Nyquist band with Sinc limitations. The interpolation filters are configured through the Interpolation Serial register. The coarse modulation will perform a real mix of each channel, independently, with either fDAC/4 or fDAC/8.
Dual Channel Complex DAC Data
The Dual Channel Complex DAC Data (also known as Single Sideband Data) is used to generate complex Tx signals (i.e., I and Q). In this mode, 12-/14-bit, interleaved I and Q data is provided to the AD9860/AD9862 and latched using either CLKOUT1 or CLKOUT2 edges as defined in the Clock Overview section of the data sheet. Both Tx paths are enabled and the two signals will be processed as a complex waveform. The Tx digital processing blocks available in this mode are the Fine Modulator (Block B), the Interpolation Filters (Block C), and the Coarse Modulator (Block D). As mentioned previously, the interpolation filters can be used to relax requirements on the external analog filters. The maximum rate of the Tx interface is 128 MSPS, i.e., 64 MSPS/channel with interleaved data (as is the case in this mode). Therefore, to fully take advantage of the DAC's maximum update rate of 128 MSPS, 2 interpolation is required. The 4 interpolation is recommended for input data rates equal to or less than 32 MSPS/channel (64 MSPS interleaved). The data bandwidth with 2 or 4 interpolation enabled is up to 37.5% of the channel input data rate. If no interpolation is enabled, the data bandwidth will be the full Nyquist band with Sinc limitations. The interpolation filters are configured through the Interpolation Serial register. A complex mix can be performed on the single sideband signal by the coarse and/or fine modulator. The coarse modulation block can be used to frequency shift the Tx signal either -fDAC/4, -fDAC/8, +fDAC/8 or + fDAC/4. The fine modulator can be used to accurately place the output signal shifting the Tx data spectrum in the positive or negative direction with a resolution of 1/226 of the DAC update rate. The fine modulator requires 4 interpolation to be enabled. The coarse modulator and fine modulator can both be used and provide a tuning range between 70% of the DAC Nyquist frequency.
The Dual Channel Real DAC Data mode is used to transmit diversity or dual channel signals. In this mode, 12-/14-bit, dual channel, interleaved Tx data is provided to the AD9860/AD9862 and latched using either CLKOUT1 or CLKOUT2 edges as defined in the Clock Overview section of the data sheet. Both Tx paths are enabled and the two signals will be processed
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BLOCK A BLOCK B BLOCK C BLOCK D LOW-PASS DECIMATION FILTER VIN+A VIN-A VIN+B VIN-B 1 PGA ADC HILBERT FILTER 1 PGA ADC RxB DATA [0:11] RxA DATA [0:11] BLOCK E
Figure 6. Receive Section Block Diagram
RECEIVE SECTION COMPONENTS
RxPGA
The receive block is configurable to process input signals of different formats and has special features such as an input buffer, gain stage, and decimation filters. The AD9860/AD9862 receive path block diagram is shown in Figure 6. The block diagram can be broken into the following stages: Input Buffer (Block A), RxPGA (Block B), dual, 10-/12-bit, 64 MSPS ADC (Block C), Decimation filter (Block D), Digital Hilbert Block (Block E), and a Data Output Multiplexer. The function of each stage is explained in the following paragraphs.
Input Buffer Stage
The RxPGA stage has a Programmable Gain Amplifier that can be used to amplify the input signal to utilize the entire input range of the ADC. The RxPGA stage provides a 0 dB to 20 dB gain range in steps of about 1 dB. The Rx channel independent gain control is accomplished through two 5-bit SPI programmable RxPGA A/B registers. The gain curve is linear in dB with a minimum gain setting (0 dB, nominally) of hex00 and a maximum gain setting (20 dB, nominally) of hex14. The RxPGA stage can provide up to a 2 V p-p signal to the ADC input.
Analog-to-Digital (A/D) Converter
The input buffer stage buffers the input signal on-chip for both receive paths. The buffer stage has two main benefits, providing a constant input impedance and reducing any "kick-back" noise that might be generated on-chip, affecting the analog input signal. The Rx path sampling mode can be split into two categories, depending on the frequency of the input signal. When sampling input signals up to Nyquist of the ADC, the sampling is referred to as Nyquist sampling. When sampling at rates above ADC Nyquist rate, the sampling is referred to as IF sampling or undersampling. For Nyquist sampling, the input buffer provides a constant 200 W impedance over the entire input signal range. The constant input impedance accommodates matching networks to ensure proper transfer of signal to the input of the device. The input buffer is self-biased to ~ 2 V, and therefore the input signal should be ac-coupled to the Rx differential input or have a common-mode voltage of about 2 V. If an external buffer is present, the internal input buffer can be bypassed and powered down to reduce power consumption. The input buffer accepts up to a 2 V p-p input signal for maximum SNR performance. Optimal THD performance occurs with 1 V p-p input signal. For IF sampling, the input buffer can be used with input signals up to about 100 MHz, the 3 dB bandwidth of the buffer. When undersampling the input signal, the output spectrum will contain an aliased version of the original, higher frequency signal. As was the case with Nyquist sampling, the input signal should be ac-coupled to the Rx differential input or have a common-mode voltage of ~ 2 V. For input signals over 100 MHz to about 250 MHz, the input buffer needs to be bypassed and an external input buffer is required. In the case that the input buffer is bypassed, the input circuit is a switched capacitor network. The switching input impedance during the sample phase is about 1/(2( )FC), where F is the input frequency and C is the input capacitance (about 4 pF). During hold mode, the input impedance is > 1 MW.
The analog-to-digital converter (ADC) stage consists of two high performance 10-/12-bit, 64 MSPS analog-to-digital (A/D) converters. The dual A/D converter paths are fully independent, except for a shared internal bandgap reference source, VREF. Each of the A/D converter's paths consists of a front-end sample and hold amplifier followed by a pipelined, switched capacitor, A/D converter. The pipelined A/D converter is divided into three sections, consisting of a 4-bit first stage followed by eight 1.5-bit stages and a final 3-bit flash. Each stage provides sufficient overlap to correct for flash errors in the preceding stages. The quantized outputs from each stage are combined into a final 12-bit result through a digital correction logic block. The pipelined architecture permits the first stage to operate on a new input sample while the remaining stages operate on preceding samples. Sampling occurs on the rising clock edge. Each stage of the pipeline, excluding the last, consists of a low resolution flash A/D connected to a switched capacitor DAC and interstage residue amplifier (MDAC). The residue amplifier magnifies the difference between the reconstructed DAC output and the flash input for the next stage in the pipeline. One bit of redundancy is used in each one of the stages to facilitate digital correction of flash errors. The last stage simply consists of a flash A/D. A stable and accurate 1.0 V bandgap voltage reference is built into the AD9860/AD9862 and is used to set a 2 V p-p differential input range. The internally generated reference should be decoupled at the VREF pin using a 10 mF and a 0.1 mF capacitor in parallel to ground. Separate top and bottom references, VRT and VRB, for each converter are generated from VREF and should also be decoupled. Recommended decoupling for the top and bottom references consists of using 10 mF and 0.1 mF capacitors in parallel between the differential reference pins, and a 0.1 mF capacitor
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from each to ground. The internal references can also be disabled (powered down) and driven externally to provide a different input voltage range or low drift reference. If an external VREF reference is used, it should not exceed 1.0 V. A Shared Reference mode allows the user to connect the differential references from both ADCs together externally for superior gain matching performance. If the ADCs are to function independently, then the reference can be left separate and will provide superior isolation between the dual channels. Shared Reference mode can be enabled through the Shared Ref register. A power-down option allows the user to power down both ADCs (sleep mode) or either ADC individually to reduce power consumption.
Decimation Stage
The output data from the dual ADCs can be multiplexed onto a single 10-/12-bit output bus. The multiplexing is synchronized using the RxSYNC output pin that indicates which channel data is on the output bus.
RECEIVE APPLICATIONS SECTION
The AD9860/AD9862 receive path (Rx) includes two high speed, high performance, 10-/12-bit ADCs. Figure 6 shows a detailed block diagram of the Rx data path and can be referred to throughout the explanation of the various modes of operation. The various Rx modes of operation are broken into three parts determined by the type of input signal: 1. Single Channel ADC Signal 2. Dual Channel Real ADC Signal (diversity or dual channel) 3. Dual Channel Complex ADC Signal (I and Q or Single Sideband). Each one of these parts is further divided into two cases, sampling input signals up to Nyquist of the ADC (Nyquist sampling) and sampling at rates above ADC Nyquist rate (IF sampling or undersampling). The AD9860/AD9862 uses oversampling and decimation filters to ease requirements on external filtering components. The decimation filters (for both receive paths) can be used or bypassed so as to accommodate different signal bandwidths and provide different output data rates to allow easy integration with several different data processing schemes. Nonbaseband data can be used in an effort to avoid the dc offsets in the receive signal path that can cause errors. By receiving nonbaseband data, the requirements of external filtering may be greatly reduced. In each of the different receive modes, the input buffer, Programmable Gain Amplifier (RxPGA), and output multiplexer remain within the receive path.
Single Channel ADC Signal
For signals with maximum frequencies less than or equal to 3/16 the ADC sampling rate, fADC, the decimate by 2 filter (or half-band filter) can be used to provide on-chip suppression of out-of- band images and noise. When data is present in frequencies greater than 1/4 fADC, the decimate by 2 filter can be disabled by switching the filter out of the circuit. The decimation filter allows the ADC to oversample the input while decreasing the output data rate by half. The two main benefits are a simplification of the input antialiasing filter and a slower data interface rate with the external digital ASIC. The decimation filter is an 11 tap filter and suppresses out of band noise by 38 dB.
Hilbert Block
The Hilbert filter is available to provide a Hilbert Transform of the data from the ADC in Channel B. The Digital Hilbert Transform, in combination with an external complex downconverter, enables a receive image rejection architecture (similar to Hartley image rejection architecture). The Hilbert filter pass-band (< 0.1 dB ripple) is between 25% to 75% of the Nyquist rate of its input data rate. The maximum data rate of the Rx Hilbert filter is 32 MSPS. At ADC rates higher than this, the decimation filters should be enabled. The Hilbert filter transfer function plots are shown in Figure 7.
0
MAGNITUDE - dB
-40
In this mode, a single input signal to be digitized is connected to the differential input pins, VIN+A and VIN-A. The 10-/12-bit output Rx data is latched using either CLKOUT1 or CLKOUT2 edges as defined in the Clock Overview section. The Rx path available options include bypassing the input buffer, Rx PGA control and using the Decimation Filter. By default, both Rx paths are enabled and the unused one should be powered down using the appropriate bit in the Rx Power-Down register, d1. The input buffer description above explains the conditions under which the buffer should be bypassed.
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If the input signal, or the undersampled alias signal for the IF sampling case, falls below 40% of the ADC Nyquist rate, the decimation filter can be enabled to suppress out-of-band noise and spurious signals by 40 dB or more. With the decimation filter enabled, the SNR of the Rx path improves by about 2.3 dB.
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 NORMALIZED - fS
Dual Channel Real ADC Signal
Figure 7. Rx Hilbert Filter, Keeping Positive Frequencies Response
Data Output Multiplexer Stage
The Rx data output format can be configured for either twos complement or offset binary. This is controlled by the Rx Twos Complement register.
The Dual Channel Real ADC Signal mode is used to receive diversity signals or dual independent channel signals that will be processed independent of each other. In this mode, the two input signals to be digitized are connected to the differential input pins of the AD9860/AD9862, VIN+A, VIN-A, VIN+B, and VIN-B. The two 10-/12-bit Rx outputs can be either interleaved onto a single 10-/12-bit bus or output in parallel on two 10-/12-bit buses.
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The output will be latched using some configuration of CLKOUT1 or CLKOUT2 edges as defined in the Clock Overview section of the data sheet. The Rx path available options include bypassing the input buffer, RxPGA control and using the decimation filter. The input buffer description above explains the conditions under which the buffer should be bypassed. If the input signal, or the undersampled alias signal for the IF sampling case, falls below 40% of the ADC Nyquist rate, the decimation filter can be enabled to suppress out-of-band noise and spurious signals by 40 dB or more. With the decimation filter enabled the SNR of the Rx path improves by about 2.3 dB.
Dual Channel Complex ADC Signal
An internal Delay Lock Loop (DLL) based clock multiplier provides a low noise, 2 or 4 multiplication of the input clock over an output frequency range of 32 MHz to 128 MHz. The DLL Fast register should be used to optimize the DLL performance. For DLL output frequencies between 32 MHz and 64 MHz, this bit should be set low. For output frequencies between 64 MHz to 128 MHz, the Fast bit should be set high (for a 64 MHz output frequency, the register can be set either high or low). The DLL can be bypassed by setting a 1 multiplication factor in the DLL Multiplier register. The DLL can be powered down when it is bypassed for power savings by setting the DLL PwrDwn register. For applications where an external crystal is desired, the AD9860/ AD9862 internal oscillator circuit and the DLL clock multiplier enable a low frequency, lower cost quartz crystal to be used to generate the input reference clock. The quartz crystal would be connected between the OSC1 and OSC2 pins with parallel resonant load capacitors as specified by the crystal manufacturer. An internal Duty Cycle Stabilizer (DCS) can be enabled on the AD9860 by setting the Clk Duty register. This provides a stable 50% duty cycle to the ADC for high speed clock rates between 40 MSPS to 64 MSPS when proper duty cycle is more critical.
System Clock Distribution Circuitry
The Dual Channel Complex ADC Signal mode is used to receive baseband I and Q signals or a single sideband signal at some IF. In this mode, a complex input signal is generated from an external quadrature demodulator. The in-phase channel (I channel) is connected to VIN+A and VIN-A, and the Quadrature Data (Q channel) is connected to the VIN+B and VIN-B differential pins. The Rx path available options include bypassing the input buffer, RxPGA control, the decimation filter, and using the digital Hilbert filter. Shared Reference mode is also discussed below. The RxPGA provides 0 dB to 20 dB gain control for both channels. The input buffer description above explains the conditions under which the buffer should be bypassed. If the input signal, or the undersampled alias signal for the IF sampling case, falls below 40% of the ADC Nyquist rate, the decimation filter can be enabled to suppress out-of-band noise and spurious signals by 40 dB or more. With the decimation filter enabled, the SNR of the Rx path improves by about 2.3 dB. A digital Hilbert filter can be enabled to provide a receive image rejection architecture on-chip. The digital Hilbert filter combines the I data and a phase shifted version of the Q data to produce a single combined Rx signal. The filter can provide 50 dB image suppression in the pass band (less than 0.1 dB ripple). The pass band of the filter is from 25% to 75% of Nyquist rate of the data entering the Hilbert filter. Note, the Hilbert filter's maximum input data rate is 32 MSPS, at ADC rates above 32 MSPS. The decimation filter is required to reduce the data rate. With the decimation filter also enabled, the pass band of the Hilbert filter will be 12.5% to 37.5% of the ADC Nyquist rate (still 25% to 75% of the Nyquist rate of the data entering the Hilbert filter). An optional Shared Reference mode allows the user to connect the differential references from the dual ADC together externally for superior gain matching performance. To enable the Shared Reference mode, the Shared Ref register (d4, b1) should be set high.
TIMING GENERATION BLOCK
There are many variables involved in the timing distribution. External variables include CLKIN, CLKOUT1, CLKOUT2, Rx Data Rate, Tx Data Rate. Internal variables include ADC conversion rate, DAC update rate, interpolation rate, decimation rate, Rx data multiplexing and Tx data demultiplexing. Many of these parameters are interrelated and based on CLKIN. Optimal power versus performance and ease of integration options can be chosen to suit a particular application.
NO DECIMATION, ADC 2 DATA MUX AND LATCH MUX OUT: REG D5 B0 Rx RETIME: REG D5 B3
Rx DATA [0:23]
DECIMATE: REG D6 B0 NO INVERSION, INVERT INV
1 , 1/2 DIV CLKSEL 1 , 1/2 CLKIN DIV ADC DIV2: REG D24 B5
CLKOUT1
INV1: REG D25 B1 1 ,2 ,4 DLL DLL MULTIPLIER: REG D24 B3, 4 1 , 1/2 , 1/4 DIV CLKOUT2 DIV FACTOR: REG 25 B6, 7 NO INTERP 2, 4 DAC INTERPOLATION: REG D19 B0, 1 NO INVERSION, INVERT INV CLKOUT2 INV2: REG D25 B5
The AD9860/AD9862 Timing Generation block uses a single external clock reference to derive all internal clocks to operate the transmit and receive channels. The input clock reference can consist of either an external single ended clock applied to the OSC1 pin, with the OSC2 pin left floating or an external crystal connected between the clock input pins (OSC1 and OSC2). By default, the AD9860/AD9862 can accept either an external reference clock or a crystal to generate the input clock. The internal oscillator, if not used, should be disabled by setting the Input Control Clock register. The OSC1 input impedance is a relatively high resistive impedance (typically, about 500 kW).
DATA LATCH AND DEMUX
Tx DATA [0:13]
CLOCK PATH DATA PATH
2 DATA PATHS: REG D19 B4 Q/I ORDER: REG D18 B5 Tx RETIME: REG D18 B6
Figure 8. Normal Operation Timing Block Diagram
One of two possible timing operation modes can be selected. The typical timing mode is called Normal Operation mode; a block diagram is shown in Figure 8. The other mode is called Alternative Operation mode, and a block diagram is shown in Figure 12. -24- REV. 0
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Table I. Rx Data Timing Table Table Ia. CLKSEL Set Logic Low
CLKSEL ADC Div 2 Decimate Multiplex No Mux No Decimation Mux No Div No Mux Decimation Mux Low No Mux No Decimation Mux Div No Mux Decimation Mux Not Allowed No Div No Mux Decimation Mux High No Mux No Decimation Mux Div No Mux Decimation Mux See Figure 8 for Relative Timing Timing No. 4 Rx Data = 2 CLKOUT1 CLKOUT1 = 12 CLKIN No Decimation Mux CLKSEL ADC Div 2
Table Ib. CLKSEL Set Logic High
Decimate Multiplex No Mux See Figure 8 for Relative Timing Timing No. 3 Rx Data = CLKOUT1 CLKOUT1 = CLKIN Timing No. 4 Rx Data(MUXED) = 2 CLKOUT1 CLKOUT1 = CLKIN Timing No. 2 Rx Data = 12 CLKOUT1 CLKOUT1 = CLKIN Timing No. 3 Rx Data(MUXED) = CLKOUT1 CLKOUT1 = CLKIN Timing No. 2 Rx Data = 12 CLKOUT1 CLKOUT1 = CLKIN Timing No. 3 Rx Data(MUXED) = CLKOUT1 CLOUT1 = CLKIN Timing No. 1 Rx Data = 14 CLKOUT1 CLOUT1 = CLKIN Timing No. 2 Rx Data(MUXED) = 12 CLKOUT1 CLKOUT1 = CLKIN
Timing No. 3 Rx Data = 2 CLKOUT1 CLKOUT1 = 12 CLKIN Timing No. 4 Rx Data(MUXED) = 2 CLKOUT1 CLKOUT1 = 12 CLKIN Timing No. 3 Rx Data = CLKOUT1 CLKOUT1 = 12 CLKIN Timing No. 4 Rx Data(MUXED) = 2 CLKOUT1 CLOUT1 = 12 CLKIN Timing No. 2 Rx Data = 12 CLKOUT1 CLOUT1 = 12 CLKIN Timing No. 3 Rx Data(MUXED) = CLKOUT1 CLKOUT1 = 12 CLKIN
fCLKOUT1
Rx DATA TIMING No. 1 fRx = CLKOUT 4 Rx DATA TIMING No. 2 fRx = CLKOUT 2 Rx DATA TIMING No. 3 fRx = CLKOUT Rx DATA TIMING No. 4 fRx = 2 CLKOUT
tR
1
tR
2
3
tR
tR
1
Figure 9. Rx Timing Diagram
ADC DIV2 A CLKIN 0: B = A 1: B = A/2 B
DLL MULT C 00: C = B 01: C = B/2 10: C = B/4
CLKOUT2 DIV D 00: D = C 01: D = C/2 10: D = C/4
INTERP E 00: E = D 01: E = 2 10: E = 4 D D TxDAC UPDATE RATE SINGLE CHANNEL (CANNOT EXCEED DLL OUTPUT RATE)
ADC SAMPLE RATE (NOT TO EXCEED 64MHz)
DLL OUTPUT RATE (NOT TO EXCEED 128MHz)
CLKOUT2
INPUT Tx DATA RATE (SINGLE CHANNEL)
Figure 10. Single Tx Timing Block Diagram, Alternative Operation
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For the Normal Operation mode, the Tx timing is based on a clock derived from the DLL output, while the Rx clock is unaffected by the DLL setting. The Alternative Operation mode, timing utilizes the output of the DLL to generate both Rx and Tx clocks. It also sets default operation of the DLL to 4 mode. Normal Operation is typically recommended because the Rx ADC is more sensitive to the jitter and noise that the DLL may generate, so its performance may degrade. The Mode/TxBlank pin logic level at power up or RESET defines in which mode the device powers up. If Mode/TxBlank is low at power up, the Normal Operation mode is configured. Otherwise, the Alternative Operation mode is configured.
Rx Path (Normal Operation)
The Rx data (unless re-timed using the Rx Retime register) is timed relative to the CLKOUT1 pin output. The Rx output data can be decimated (halving the data rate) or both channels can be multiplexed onto the channel A data bus (doubling the data rate). Decimation enables oversampling while maintaining a slower external data transfer rate and provides superior suppression of out of band signals and noise. Multiplexing enables fewer digital output bits to be used to transfer data from the Rx path to the digital ASIC collecting the data. When Mux Mode is enabled with an output data rate equal to CLKOUT1 (Timing No. 3 in Figure 9) then the RxSync pin is required to identify which channel's output data is on the output data bus. RxSync output is aligned with the output data, and by default a logic low indicates data from Rx Channel B is currently on the output data bus. If RxSync is logic high, then data from Rx Channel A is currently on the output data bus. The Inv RxSync register can be used to switch this notation. The CLKOUT1 pin outputs a clock at the frequency of CLKIN or CLKIN/2 depending on the voltage level applied to the CLKSEL pin. If a logic low is applied to CLKSEL, CLKOUT1 will run at half the CLKIN rate, if CLKSEL is set to logic high CLKOUT1 outputs a clock equal to CLKIN. This timing flexibility along with the invert option for CLKOUT1, controlled by the Inv 1 register allow for various methods of latching data from the Rx path to the digital ASIC, which will process the data. These options are shown in Table Ia and Ib along with a timing diagram in Figure 9. Not shown is the option to invert CLKOUT1, controlled by the Inv 1 register. For this mode, relative timing remains the same except the opposite edges of CLKOUT1 would be used.
The ADC sampling rate, the Rx data output rate, and the rate of CLKOUT1 (clock used to latch output data) are the parameters of interest for the receive path data. These parameters in addition to the data bandwidth are related to CLKIN by decimation filters, divide by two circuits, data multiplexer logic and retiming latches. The Rx path timing can be broken into two separate relationships: the ADC sample rate relative to the input clock, CLKIN and the output data rate relative to CLKOUT1. The ADCs sample rate relative to CLKIN is controlled by the ADC Div2 register and the sample rate can be equal to or one half of the input clock rate. The output data relative to CLKOUT1 has many configurations providing a flexible interface. The different options are shown in Figure 8. Table Ia and Ib describe the setup required to obtain the desired data timing. RxSync is available when the Rx data is decimated and multiplexed to identify which channel data is present at the output bus.
ADC DIV2 A CLKIN 0: B = A 1: B = A/2 B
DLL MULT C 00: C = B 01: C = 2 10: C = 4 B B
CLKOUT2 DIV D 00: D = C 01: D = C/2 10: D = C/4
2 EDGES
DUAL CHANNEL FACTOR E F F = E/2
INTERP G 00: G = F 01: G = 2 10: G = 4 F F TxDAC UPDATE RATE EACH CHANNEL (CANNOT EXCEED DLL OUTPUT RATE)
0: E = D 1: E = 2
D
ADC SAMPLE RATE (NOT TO EXCEED 64MHz)
DLL OUTPUT RATE (NOT TO EXCEED 128MHz)
CLKOUT2
INPUT Tx DATA RATE
INPUT Tx DATA RATE EACH CHANNEL
Figure 11. Dual Tx Timing Block Diagram, Alternative Operation
fCLKOUT2
Tx DATA TIMING No. 1 fTx = CLKOUT2 Tx DATA TIMING No. 2 fTx = 2 CLKOUT2
fT 1 fT 2
fT 3 fT 4
Figure 12. Tx Timing Diagram
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Tx Path (Normal Operation)
The DAC update rate, the Tx input data rate, and the rate of CLKOUT2 (clock used to latch Tx input data) are the parameters of interest for the transmit path data. These parameters, in addition to the output signal bandwidth, are related to CLKIN by the settings of the ADC Div2, the DLL multiplier, the CLKOUT2 Div, the two edges, and the interpolation registers. The Tx data is timed relative to the CLKOUT2 pin (unless it is retimed relative to CLKOUT1 by setting Tx Retime register) and the input Tx data is latched on either each rising edge, each falling edge or both edges (controlled through the Inverse Sample and two edges registers). The timing diagrams for these cases are shown in Figure 12. The Dual Tx data is multiplexed onto a single bus so that fewer digital bits are necessary to transfer data. Throughout this discussion of Tx path timing, Tx digital processing options other than interpolation are ignored because they do not change data timing; Tx data timing reflects whether single or dual channel data is latched into the AD9860/AD9862. The rates of CLKOUT2 (and the input data rate) are related to CLKIN by the DLL Multiplier Register, the setting of the CLKOUT2 Divide Factor Register and the register ADC Div2. These relationships are shown in Table II.
Table II. CLKOUT2 Timing Relative to CLKIN for Normal Operation Mode
CLK DIV2
DLL Mult 1
CLKOUT2 Div Factor 1 2 4 1 2 4 1 2 4 1 2 4 1 2 4 1 2 4
CLKOUT2 CLKIN CLKIN/2 CLKIN/4 2 CLKIN CLKIN CLKIN/2 4 CLKIN 2 CLKIN CLKIN CLKIN/2 CLKIN/4 CLKIN/8 CLKIN CLKIN/2 CLKIN/4 2 CLKIN CLKIN CLKIN/2
No Div
2
4
1
Div by 2
2
4
NO DECIMATION, 1 , 1/2 DIV ADC DIV2: REG D24 B5 1 , 1/2 DIV 1 ,2 ,4 CLKIN DLL CLKSEL 1 , 1/2 , 1/4 DIV CLKOUT2 DIV FACTOR: REG 25 B6, 7 ADC
2 DATA MUX AND LATCH Rx DATA [0:23]
DECIMATE: REG D6 B0
MUX OUT: REG D5 B0 Rx RETIME: REG D5 B3
NO INVERSION, INVERT INV INV1: REG D25 B1 NO INVERSION, INVERT INV INV2: REG D25 B5 CLKOUT2 CLKOUT1
DLL MULTIPLIER: REG D24 B3, 4
NO INTERP, 2, 4 DAC INTERPOLATION: REG D19 B0, 1
DATA LATCH AND DEMUX 2 DATA PATHS: REG D19 B4 Q/I ORDER: REG D18 B5 Tx RETIME: REG D18 B6
Tx DATA [0:13]
CLOCK PATH DATA PATH
Figure 13. Alternative Operation Timing Block Diagram
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The timing block diagrams in Figures 10 and 11 show how the various clocks of the single and dual Tx path are affected by the various register settings. For dual Tx data, an option to redirect demultiplexed data to either path is available. For example, the AD9860/AD9862 can accept complex data in the form of I then Q data or Q then I data, controlled through QI Order register. For the dual Tx data cases, the Tx_SYNC Pin input logic level defines what data is currently on the Tx data bus. By default, when Tx_SYNC is low, Channel A data (first of the set) should be on the data bus; if TxSYNC is high, Channel B data (or the second of the set) should be on the Tx bus. This can be reversed be setting the Inv TxSYNC register.
Rx Path (Alternative Timing Operation)
pin. If a logic low is applied to CLKSEL, CLKOUT1 will run at half the CLKIN rate; if CLKSEL is set to logic high, CLKOUT1 outputs a clock equal to CLKIN. This timing flexibility, along with the invert option for CLKOUT1 controlled by the Inv 1 Register, allows for various methods of latching data from the Rx path to the digital ASIC, which will process the data. These options are shown in Table Ia and Ib along with a timing diagram in Figure 9. Not shown is the option to invert CLKOUT1, controlled by the Inv 1 register. For this mode, relative timing remains the same except the opposite edges of CLKOUT1 would be used. Overall, relative timing can be found by using the Alternative Operation Mode Master Timing Guide in Table V and using Rx timing shown in Figure 9.
Tx Path (Alternative Timing Operation)
The ADC sampling rate, the Rx data output rate and the rate of CLKOUT1 (clock used to latch output data) are the parameters of interest for the receive path data. These parameters, in addition to the data bandwidth, are related to CLKIN by decimation filters, divide by two circuits, data multiplexer logic retiming latches and also the DLL multiplication setting (which is not the case for Normal Operation mode). This mode can be configured by default by forcing the Tx_Blank_In pin to a logic high level during power up. The Rx path timing can be broken into two separate relationships: the ADC sample rate relative to the input clock, CLKIN and the output data rate relative to CLKOUT1. The ADCs sample rate relative to CLKIN is controlled by the ADC Div2 register and the DLL Multiplier register. The sample rate can be equal to or one half of the DLL output clock rate. The output data rate relative to CLKOUT1 for the Alternative Operation Mode has the same configuration options as in the Normal Operation Mode. The different options are shown in Figure 9. Table Ia. and Ib. describe the setup required to obtain the desired data timing. The Rx data (unless retimed using the Rx Retime register) is timed relative to the CLKOUT1 pin output. The Rx output data can be decimated (halving the data rate) or both channels can be multiplexed onto the Channel A data bus (doubling the data rate). Decimation enables oversampling while maintaining a slower external data transfer rate and provides superior suppression of out of band signals and noise. Multiplexing enables fewer digital output bits to be used to transfer data from the Rx path to the digital ASIC collecting the data. When Multiplexing mode is enabled with an output data rate equal to CLKOUT1 (Timing No. 3 in Figure 9), then the RxSync pin is required to identify which channel's output data is on the output data bus. RxSync output is aligned with the output data and by default, a logic low indicates data from Rx Channel B is currently on the output data bus. If RxSync is logic high, then data from Rx Channel A is currently on the output data bus. The Inv RxSync register can be used to switch this notation. The CLKOUT1 pin outputs a clock at a frequency of CLKIN or CLKIN/2 depending on the voltage level applied to the CLKSEL
The DAC update rate, the Tx input data rate and the rate of CLKOUT2 (clock used to latch Tx input data) are the parameters of interest for the transmit path data. These parameters in addition to the output signal bandwidth are related to CLKIN by the settings of the DLL multiplier, the CLKOUT2 Div, the two edge and the Interpolation registers (in this mode, the ADC Div2 register does not affect Tx timing). The Tx data is timed relative to the CLKOUT2 pin (unless it is retimed relative to CLKOUT1 by setting Tx Retime register) and remains the same as it does in Normal Operation Mode. The input Tx data is latched on each rising edge, each falling edge or both edges (controlled through the Inverse Sample and two edge registers). The timing diagrams for these cases are shown in Figure 12. The Dual Tx data is multiplexed onto a single bus so that fewer digital bits are necessary to transfer data. Throughout this discussion of Tx path timing, Tx digital processing options other than interpolation are ignored because they do not change data timing; Tx data timing reflects whether single or dual channel data is latched into the AD9860/AD9862. The rates of CLKOUT2 (and the input data rate) are related to CLKIN by the DLL Multiplier register and the setting of the CLKOUT2 Divide Factor register. These relationships are shown in Table III.
Table III. CLKOUT2 Timing Relative to CLKIN In Alternative Operation Mode
DLL Mult 1
CLKOUT2 Div Factor 1 2 4 1 2 4 1 2 4
CLKOUT2 CLKIN CLKIN/2 CLKIN/4 2 CLKIN CLKIN CLKIN/2 4 CLKIN 2 CLKIN CLKIN
2
4
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Table IV. Normal Operation Mode Master Timing Guide
ADC Data Rate1 (MSPS)
Dual DAC Data Rate2 (MSPS) DAC Update Rate CLKOUT1 2 CLKOUT2
ADC DLL Clock ADC2 Mult Rate Non-MUX Mode e MUX Mode
No Deci Deci by 2 No Deci Deci by 2
1 Interp
2 Interp
4 CLKSEL CLKSEL CLKDIV CLKDIV CLKDIV Interp = Low = High =1 = 1 2 = 1 4 CLKIN 2 CLKIN 4 CLKIN CLKIN CLKIN 2 CLKIN 2 CLKIN 2 CLKIN CLKIN 2 CLKIN 2 CLKIN CLKIN 4 CLKIN 2 CLKIN CLKIN 4 CLKIN 2
0
1
2 CLKIN CLKIN CLKIN CLKIN 2 CLKIN CLKIN 2 CLKIN CLKIN 2 CLKIN 4 2 2 CLKIN CLKIN CLKIN CLKIN 4 8 2 4 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN 2 2 4 CLKIN CLKIN 2 2 CLKIN CLKIN 4 2 CLKIN CLKIN CLKIN CLKIN CLKIN 2 2 2 2 4 CLKIN CLKIN CLKIN CLKIN
0
2
0
4
CLKIN CLKIN 8 CLKIN 4 CLKIN 2
1
1
1
2
1
4
NOTES 1100 MHz rate max. 2 Single DAC data rate = 12 dual DAC data rate.
Table V. Alternative Operation Mode Master Timing Guide
ADC Data Rate1 (MSPS)
Dual DAC Data Rate2 (MSPS) DAC Update Rate CLKOUT1 2 CLKOUT2
ADC DLL ADC2 Clock Mult Rate
Non-MUX Mode (two buses)
MUX Mode (one bus)
No Deci Deci by 2 No Deci Deci by 2
1 Interp
2 Interp
4 CLKSEL CLKSEL CLKDIV CLKDIV CLKDIV Interp = Low = High =1 = 1 2 = 1 4 CLKIN 2 CLKIN 2 CLKIN CLKIN 2 CLKIN 2 CLKIN CLKIN 2 CLKIN 4 CLKIN CLKIN 2 CLKIN 4 CLKIN CLKIN 2 CLKIN 2 CLKIN CLKIN 2 CLKIN 2 CLKIN CLKIN 4 CLKIN 2
0
1
CLKIN CLKIN 2 2 CLKIN CLKIN 4 4 CLKIN CLKIN CLKIN CLKIN 2 2 CLKIN CLKIN 2 2 CLKIN CLKIN
CLKIN 2 2 CLKIN CLKIN 4 CLKIN
CLKIN CLKIN
2 CLKIN CLKIN CLKIN CLKIN 2
0
2
2 4 2 2 2 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN 4 4 8 4 2 4 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN 2 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN 2 2 2 4 2 2 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN 2 8 4 4 2 4 CLKIN CLKIN CLKIN CLKIN CLKIN CLKIN
0
4
8 2 CLKIN CLKIN CLKIN CLKIN 4 CLKIN 2 2 CLKIN 4 CLKIN CLKIN
CLKIN CLKIN 4 CLKIN 2
1
1
1
2
1
4
CLKIN
NOTES 1100 MHz rate max. 2 Single DAC data rate = 12 dual DAC data rate.
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AD9860/AD9862
The timing block diagrams in Figures 14 and 15 show how the various clocks of the single and dual Tx path are affected by the various register settings. For dual Tx data, an option to redirect demultiplexed data to either path is available. For example, the AD9860/AD9862 can accept complex data in the form of I then Q data or Q then I data, controlled through QI Order register. For the dual Tx data cases, the Tx_SYNC pin input logic level defines what data is currently on the Tx data bus. By default, when Tx_SYNC is low, Channel A data (first of the set) should be on the data bus. If TxSYNC is high, Channel B data (or the second of the set) should be on the Tx bus. This can be reversed by setting the Inv TxSYNC register.
ADDITIONAL FEATURES
The AUX ADC A multiplexer controls whether pin AUX_ADC_A1 or pin AUX_ADC_A2 is connected to the input of Auxiliary ADC A. The multiplexer is programmed through Register D34 B1, SelectA. By default, the register is low, which connects the AUX_ADC_A2 Pin to the input. Similarly, AUX ADC B has a multiplexed input controlled by Register D34 B4, SelectB. The default setting for SelectB is low, which connects the AUX_ADC_B2 input pin to AUX ADC B. If the SelectA or SelectB register bit is set high, then the AUX_ADC_A1 Pin or the AUX_ADC_B1 pin is connected to the respective AUX ADC input. An internal reference buffer provides a full-scale reference for both of the auxiliary ADCs that is equal to the supply voltage for the auxiliary ADCs. An external full-scale reference can be applied to either or both of the AUX ADCs by setting the appropriate bit(s), RefselB for the AUX ADC B and Refsel A for the AUX ADC B in the Register Map. Setting either or both of these bits high will disconnect the internal reference buffer and enable the externally applied reference from the AUX_REF Pin to the respective channel(s). Timing for the auxiliary ADCs is generated from a divided down Rx ADC clock. The divide down ratio is controlled by register D35 B0, CLK/4 and is used to maintain a maximum clock rate of 20 MHz. By default, CLK/4 is set low dividing the Rx ADC clock by 2; this is acceptable when running the Rx ADC at rate of 40 MHz or less. At Rx ADC rate greater than 40 MHz, the CLK/4 register bit should be set high and will divide the Rx ADC clock by 4 to derive the auxiliary ADC Clock. The conversion time, including setup, takes 16 clock cycles (16 Rx ADC clock cycles); when CLK/4 is set low, divide by 2 mode, or 32 clock cycles when CLK/4 is set high.
In addition to the features mentioned above in the transmit, receive and clock paths, the AD9860/AD9862 also integrates components typically required in communication systems. These components include auxiliary analog-to-digital converters (AUX ADC), auxiliary digital-to-analog converters (AUX DAC), and a sigma-delta output.
Auxiliary ADC
Two auxiliary 10-bit SAR ADCs are available for various external signals throughout the system, such as a Receive Signal Strength Indicator (RSSI) function or Temperature Indicator. The auxiliary ADCs can convert at rates up to 1.25 MSPS and have a bandwidth of around 200 kHz. The two auxiliary ADCs (AUX ADC A and AUX ADC B) have multiplexed inputs, so that up to four system signals can be monitored.
DLL MULT A CLKIN 00: B = A 01: B = 2 10: B = 4 A A B
CLKOUT2 DIV C 00: C = B 01: C = B/2 10: C = B/4
INTERP D 00: D = C 01: D = 2 10: D = 4 C C TxDAC UPDATE RATE SINGLE CHANNEL (CANNOT EXCEED DLL OUTPUT RATE)
ADC SAMPLE RATE (NOT TO EXCEED 64MHz)
DLL OUTPUT RATE (NOT TO EXCEED 128MHz)
CLKOUT2
INPUT Tx DATA RATE (SINGLE CHANNEL)
Figure 14. Single Tx Timing Block Diagram, Alternative Operation
DLL MULT A CLKIN 00: B = A 01: B = 2 10: B = 4 A A B
CLKOUT2 DIV C 00: C = B 01: C = B/2 10: C = B/4
2 EDGES
DUAL CHANNEL FACTOR D E E = D/2
INTERP F 00: F = G 01: F = 2 10: F = 4 G G TxDAC UPDATE RATE EACH CHANNEL (CANNOT EXCEED DLL OUTPUT RATE)
0: D = C 1: D = 2
C
ADC SAMPLE RATE (NOT TO EXCEED 64MHz)
DLL OUTPUT RATE (NOT TO EXCEED 128MHz)
CLKOUT2
INPUT Tx DATA RATE
INPUT Tx DATA RATE EACH CHANNEL
Figure 15. Dual Tx Timing Block Diagram, Alternative Operation
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AD9860/AD9862
Conversion is initiated by writing a logic high to one or both of the Start register bits, Register D34 B0 (StartA) and D34 B3 (StartB). When the conversion is complete, the straight binary, 10-bit output data of the AUX ADC is written to one of four reserved locations in the register map depending on which auxiliary ADC and which multiplexed input is selected. Because the auxiliary ADCs output 10 bits, two register addresses are needed for each data location. Initiating a conversion or retrieving data can also be accomplished either through the standard Serial Port Interface by reading and writing to the appropriate registers or through a dedicated Auxiliary Serial Port Interface (AUX SPI). The AUX SPI can be configured to allow fast access and control of either one of the auxiliary ADCs and is available so that the SPI is not tied up retrieving auxiliary ADC data. The AUX SPI can be enabled and configured by setting register AUX ADC CTRL. Setting register use pins high enables the AUX SPI port. Setting register Sel BnotA low connects auxiliary ADC A to the AUX SPI port, while setting it high connects auxiliary ADC B to the AUX SPI port. As mentioned above, setting the appropriate Select bit selects which of the multiplexed input is connected to the auxiliary ADC. The AUX SPI consists of a chip select pin (AUX_SPI_csb), a clock pin (AUX_SPI_clk), and a data output pin (AUX_SPI_do). A conversion is initiated by pulsing the AUX_SPI_csb pin low. When the conversion is complete, the data pin, AUX_SPI_do, previously a logic low, will go high. At this point, the user supplies an external clock, previously tied low, no data is present on the first rising edge. The data output bit is updated on the falling edge of the clock pulse and is settled and can be latched on the next clock rising edge. The data arrives serially, MSB first. The AUX SPI runs up to a rate of 16 MHz.
AUX DAC
The AD9860/AD9862 has three 8-bit voltage output auxiliary DACs, AUX DACs. The AUX DACs are available for supplying various control voltages throughout the system such as a VCXO voltage control or external VGA gain control and can typically sink or source up to 1 mA. An internal voltage reference buffer provides a full-scale voltage reference for both of the AUX DACs equal to the supply voltage for the AUX DACs. The straight binary input codes are written to the appropriate registers. If the Slave Mode register bit is high, slave mode enabled, the AUX DAC(s) update will occur when the appropriate update register is written to. Otherwise, the update will occur at the conclusion of the data being written to the register. Typical maximum settling time for the auxiliary DAC is around 6 ms. Other optional controls include an invert register control and a power down option. The invert register control, i.e., instead of hexFF being high and hex00 being low, hex00 is high, and hexFF will be minimum setting.
Sigma-Delta
A 12-bit sigma-delta (SD) output is available to provide an additional control voltage. The SD control word is written to Registers D42, 43; SD [11:4] are the 8 MSBs and SD [3:0] are the 4 LSBs. The 12-bit word is processed by a sigma-delta modulator and produces 1-bit data at an oversampled rate equal to 1/8 of the receive ADC's sampling rate (up to 8 MSPS). The 1-bit data then feeds a 1-bit DAC. The 1-bit DAC exhibits perfect linearity. An external low-pass filter at the output should be used to low-pass filter the pulse modulated data to produce a linear output control voltage.
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AD9860/AD9862
OUTLINE DIMENSIONS 128-Lead Plastic Quad Flatpack [LQFP] (ST-128B)
Dimensions shown in millimeters
16.00 BSC 0.75 0.60 0.45 1.60 MAX
128 1
14.00 BSC
103 102
SEATING PLANE
20.00 BSC
TOP VIEW
(PINS DOWN)
22.00 BSC
1.45 1.40 1.35
10 6 2
0.20 0.09
VIEW A
7 0
38 39 65 64
SEATING PLANE
0.08 MAX COPLANARITY
VIEW A
ROTATED 90 CCW
0.50 BSC
0.27 0.22 0.17
COMPLIANT TO JEDEC STANDARDS MS-026BHB
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PRINTED IN U.S.A.
C02970-0-11/02(0)

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