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Preliminary Technical Data
FEATURES
40-channel DAC in 80 Lead LQFP and 100 Ball CSPBGA Guaranteed monotonic to 14 bits Maximum output voltage span of 4 x VREF (20 V) Nominal output voltage range of -4 V to +8 V Multiple, Independent output spans available System calibration function allowing user-programmable offset and gain Channel grouping and addressing features Thermal Monitor Function DSP/microcontroller-compatible serial interface LVDS serial interface 2.5 V to 5.5 V JEDEC-compliant digital levels
DVCC VDD VSS AGND DNGD
40-Channel, 14-Bit Serial Input, Voltage-Output DAC AD5371
Power-on reset Digital reset (RESET) Clear function to user-defined SIGGND (CLR pin) Simultaneous update of DAC outputs (LDAC pin)
APPLICATIONS
Level setting in automatic test equipment (ATE) Variable optical attenuators (VOA) Optical switches Industrial control systems Instrumentation
FUNCTIONAL BLOCK DIAGRAM
LDAC
VREF0 CONTROL REGISTER 14 14 8 14 14 14 14 SPI/LVDS SYNC SDI SCLK SYNC SDI SCLK SDO BUSY 8 RESET CLR STATE MACHINE 14 14 14 14 14 A/B SELECT REGISTER X1A REGISTER X1B REGISTER M REGISTER C REGISTER 8 MUX 1 14 14 14 TO MUX 2's 14 X2A REGISTER X2B REGISTER MUX 14 2 14 OFS1 14 REGISTER DAC 0 14 REGISTER OFFSET DAC 1 BUFFER DAC 0 OUTPUT BUFFER AND POWER DOWN CONTROL VOUT8 VOUT9 VOUT10 VOUT11 VOUT12 VOUT13 VOUT14 VOUT15 SIGGND1 SERIAL INTERFACE 14 14 14 14 A/B SELECT REGISTER X1A REGISTER X1B REGISTER M REGISTER C REGISTER 8 MUX 1 14 14 14 TO MUX 2's 14 X2A REGISTER X2B REGISTER MUX 14 2 OFS0 REGISTER 14 OFFSET DAC 0 BUFFER DAC 0 14 REGISTER DAC 0 OUTPUT BUFFER AND POWER DOWN CONTROL BUFFER GROUP 0
VOUT0 VOUT1 VOUT2 VOUT3 VOUT4 VOUT5 VOUT6 VOUT7
SIGGND0
* * * * * *
* * * * * *
MUX 1
X1A REGISTER X1B REGISTER M REGISTER C REGISTER
14 14
* * * * * *
14
* * * * * *
14
* * * * * *
X2A REGISTER X2B REGISTER
MUX 14 2
* * * * * *
* * * * * *
DAC 7 REGISTER
* * * * * *
14 DAC 7
* * * * * *
OUTPUT BUFFER AND POWER DOWN CONTROL
GROUP 1
VREF1
POWER-ON RESET
14 14 14 14
* * * * * *
* * * * * *
MUX 1
X1A REGISTER X1B REGISTER M REGISTER C REGISTER
14 14
* * * * * *
14
* * * * * *
14
* * * * * *
* * * * * *
MUX 14 2
* * * * * *
DAC 7 REGISTER
* * * * * *
14 DAC 7
* * * * * *
OUTPUT BUFFER AND POWER DOWN CONTROL
X2A REGISTER X2B REGISTER
AD5371
GROUPS 2 TO 4 SAME AS GROUP 1
VREF2 SUPPLIES GROUPS 2 TO 4
VREF2 VOUT16 TO VOUT39
5371-0001
SIGGND2
SIGGND3
SIGGND4
Figure 1.
AD5371--Protected by U.S. Patent No. 5,969,657; other patents pending
Rev. PrF
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. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. www.analog.com Tel: 781.329.4700 Fax: 781.326.8703 (c) 2006 Analog Devices, Inc. All rights reserved.
Preliminary Technical Data TABLE OF CONTENTS
Specifications......................................................................................4 AC Characteristics........................................................................ 5 Timing Characteristics ................................................................ 6 Absolute Maximum Ratings.............................................................9 ESD Caution.................................................................................. 9 Terminology .....................................................................................12 Functional Description ...................................................................13 DAC Architecture--General..................................................... 13 Channel Groups.......................................................................... 13 A/ B Registers And Gain/Offset Adjustment.......................... 14 Load DAC.................................................................................... 14 Offset DACs ................................................................................ 14 Output Amplifier........................................................................ 15 Transfer Function ....................................................................... 15 Reference Selection .................................................................... 15 Calibration................................................................................... 16 Calibration Example .................................................................. 16 Reset Function ............................................................................ 16
AD5371
Clear Function ............................................................................ 16 Power-Down Mode.................................................................... 17 Thermal Monitor Function....................................................... 17 Toggle Mode................................................................................ 17 Serial Interface .................................................................................18 SPI Interface ................................................................................ 18 LVDS Interface............................................................................ 18 SPI Write Mode .......................................................................... 18 SPI Readback Mode ................................................................... 19 LVDS Operation......................................................................... 19 Register Update Rates ................................................................ 19 Channel Addressing And Special Modes................................ 19 Special Function Mode.............................................................. 20 Power Supply Decoupling ......................................................... 22 Power Supply Sequencing ......................................................... 22 Interfacing Examples ................................................................. 23 Outline Dimensions ........................................................................24 Ordering Guide .......................................................................... 24
REVISION HISTORY
Pr B1 Pr. B2 Pr. B3 Pr. B4 Pr F Changed DIN to SDI Added Reset Function text Added Power Down Mode text Added Terminology and Power Supply Sequencing sections Rewrote Calibration section. Changed SPI read diagram
Rev. PrF | Page 2 of 25
Preliminary Technical Data
General Description
AD5371
The AD5371 has a high-speed serial interface, which is compatible with SPI(R), QSPITM, MICROWIRETM, and DSP interface standards and can handle clock speeds of up to 50 MHz. It also has a 100 MHz Low Voltage Differential Signaling (LVDS) serial interface compliant with EIA-644 specification. The DAC outputs are updated on reception of new data into the DAC registers. All the outputs can be updated simultaneously by taking the LDAC input low. Each channel has a programmable gain and an offset adjust register. Each DAC output is amplified and buffered on-chip with respect to an external SIGGND input. The DAC outputs can also be switched to SIGGND via the CLR pin.
The AD5371 contains 40, 14-bit DACs in a single, 80-lead, LQFP package. It provides buffered voltage outputs with a span 4 times the reference voltage. The gain and offset of each DAC can be independently trimmed to remove errors. For even greater flexibility, the device is divided into blocks of 8 DACs, and the output range of each block can be independently adjusted by an offset DAC. Group 0 can be adjusted by Offset DAC 0, group 1 can be adjusted by Offset DAC 1 and group 2 to group 4 can be adjusted by Offset DAC 2. The AD5371 offers guaranteed operation over a wide supply range with VSS from -4.5 V to -16.5 V and VDD from +8 V to +16.5 V. The output amplifier headroom requirement is 1.4 V operating with a load current of 1 mA.
Table 1. High Channel Count Bipolar DACs
Model AD5360BCPZ AD5360BSTZ AD5361BCPZ AD5361BSTZ AD5362BCPZ AD5362BSTZ AD5363BCPZ AD5363BSTZ AD5370BCPZ AD5370BSTZ AD5371BCPZ AD5371BSTZ AD5372BCPZ AD5372BSTZ AD5373BCPZ AD5373BSTZ Resolution 16 Bits 16 Bits 14 Bits 14 Bits 16 Bits 16 Bits 14 Bits 14 Bits 16 Bits 16 Bits 14 Bits 14 Bits 16 Bits 16 Bits 14 Bits 14 Bits Nominal Output Span 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (20 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) 4 x V REF (12 V) Output Channels 16 16 16 16 8 8 8 8 40 40 40 40 32 32 32 32 Linearity Error (LSB) 4 4 1 1 4 4 1 1 4 4 1 1 4 4 1 1 Package Description 56-Lead LFCSP 52-Lead LQFP 56-Lead LFCSP 52-Lead LQFP 56-Lead LFCSP 52-Lead LQFP 56-Lead LFCSP 52-Lead LQFP 64-Lead LFCSP 64-Lead LQFP 100-Ball CSPBGA 80-Lead LQFP 56-Lead LFCSP 64-Lead LQFP 56-Lead LFCSP 64-Lead LQFP Package Option CP-56 ST-52 CP-56 ST-52 CP-56 ST-52 CP-56 ST-52 CP-64 ST-64 BC-100-2 ST-80 CP-56 ST-64 CP-56 ST-64
Rev. PrF | Page 3 of 25
Preliminary Technical Data SPECIFICATIONS
AD5371
DVCC = 2.3 V to 5.5 V; VDD = 8 V to 16.5 V; VSS = -4.5 V to -16.5 V; VREF = 3 V; AGND = DGND = SIGGND = 0 V; RL = Open Circuit; Gain (m), Offset (c) and DAC Offset registers at default values; all specifications TMIN to TMAX, unless otherwise noted. Table 2.Performance Specifications
Parameter ACCURACY Resolution Relative Accuracy Differential Nonlinearity Offset Error Gain Error Offset Error2 Gain Error2 Gain Error of Offset DAC VOUT Temperature Coefficient DC Crosstalk2 REFERENCE INPUTS (VREF0, VREF1, VREF2)2 VREF Input Current VREF Range SIGGND INPUT (SIGGND0 TO SIGGND4)2 DC Input Impedance Input Range OUTPUT CHARACTERISTICS2 Output Voltage Range Nominal Output Voltage Range Short Circuit Current Load Current Capacitive Load Stability DC Output Impedance DIGITAL INPUTS Input High Voltage Input Low Voltage Input Current Input Capacitance2 DIGITAL OUTPUTS (SDO, BUSY) Output Low Voltage Output High Voltage (SDO) High Impedance Leakage Current High Impedance Output Capacitance B Version1 14 1 1 20 20 100 100 35 5 1.5 Unit Bits LSB max LSB max mV max mV max V max V max mV max ppm FSR/C typ mV max Test Conditions/Comments2
Guaranteed monotonic by design over temperature. Before Calibration Before Calibration After Calibration After Calibration Positive or Negative Full Scale. See Offset DACs section for details Includes linearity, offset, and gain drift. Typically 100 V. Measured channel at mid-scale, fullscale change on any other channel
60 2/5 55 0.5 VSS + 1.4 VDD - 1.4 -4 to +8 10 1 2 0.5 1.7 2.0 0.8 0.7 1 10 0.5 DVCC - 0.5 5 10
nA max V min/max k min V min/max V min V max V mA max mA max nF max max V min V min V max V A max pF max V max V min A max pF typ
Per input. Typically 30 nA. 2% for specified operation. Typically 60 k.
ILOAD = 1 mA. ILOAD = 1 mA.
JEDEC compliant. DVCC = 2.3 V to 3.6 V. DVCC = 3.6 V to 5.5 V. DVCC = 2.5 V to 5.5 V. DVCC = 2.3 V to 2.7 V. Except CLR and RESET
Sinking 200 A. Sourcing 200 A. SDO only.
Rev. PrF | Page 4 of 25
Preliminary Technical Data
Parameter LVDS INTERFACE - Reduced Range Link Digital Inputs2 Input Voltage Range Input Differential Threshold External Termination Resistance B Version1 Unit Test Conditions/Comments2
AD5371
Differential Input Voltage POWER REQUIREMENTS DVCC VDD VSS Power Supply Sensitivity2 Full Scale/ VDD Full Scale/ VSS Full Scale/ VCC DICC IDD ISS Power Dissipation Power Dissipation Unloaded (P) Junction Temperature3
875/1575 -- 0.1/0.1 80/120 100 132 100 2.3/5.5 8/16.5 -4.5/-16.5 -75 -75 -90 2 14 14 250 130
mV min/max V min/max min/max typ max mV min V min/max V min/max V min/max dB typ dB typ dB typ mA max mA max mA max mW C max
VCC = 5.5 V, VIH = VCC, VIL = GND. Outputs unloaded. Outputs unloaded. VSS = -5.5 V, VDD = +9.5 V, DVCC = 2.5 V TJ = TA + PTOTAL x J.
1 2
Temperature range for B Version: -40C to +85C. Typical specifications are at 25C. Guaranteed by design and characterization, not production tested. 3 Where J represents the package thermal impedance.
AC CHARACTERISTICS
DVCC = 2.5; VDD = 15 V; VSS = -15 V; VREF = 3 V; AGND = DGND = SIGGND = 0 V; CL = 200 pF to GND; RL = 10 k to GND; Gain (m), Offset (c) and DAC Offset registers at default values; all specifications TMIN to TMAX, unless otherwise noted. Table 3. AC Characteristics
Parameter DYNAMIC PERFORMANCE Output Voltage Settling Time Slew Rate Digital-to-Analog Glitch Energy Glitch Impulse Peak Amplitude Channel-to-Channel Isolation DAC-to-DAC Crosstalk Digital Crosstalk Digital Feedthrough Output Noise Spectral Density @ 10 kHz b Version1 TBD 30 1 20 10 100 40 10 0.1 1 250 Unit s typ s max V/s typ nV-s typ mV max dB typ nV-s typ nV-s typ nV-s typ nV-s typ nV/(Hz)1/2 typ Test Conditions/Comments Full-scale change
VREF(+) = 2 V p-p, 1 kHz. Between DACs inside a group. Between DACs from different groups. Effect of input bus activity on DAC output under test. VREF = 0 V.
1
Guaranteed by design and characterization, not production tested.
Rev. PrF | Page 5 of 25
Preliminary Technical Data
TIMING CHARACTERISTICS
AD5371
DVCC = 2.3 V to 5.5 V; VDD = 8 V to 16.5 V; VSS = -4.5 V to -16.5 V; VREF = 3 V; AGND = DGND = SIGGND = 0 V; RL = Open Circuit; Gain (m), Offset (c) and DAC Offset registers at default values; all specifications TMIN to TMAX, unless otherwise noted.
SPI INTERFACE (Figure 4 and Figure 5) Parameter1, 2, 3 t1 t2 t3 t4 t5 t6 t7 t8 t93 t10 t11 t12 t13 t14 t15 t16 t17 t18 t19 t20 t21 t225 Limit at TMIN, TMAX 20 8 8 11 20 10 5 5 42 1.25 500 20 10 3 0 3 20/30 125 30 400 270 25 Unit ns min ns min ns min ns min ns min ns min ns min ns min ns max s max ns max ns min ns min Description SCLK Cycle Time. SCLK High Time. SCLK Low Time. SYNC Falling Edge to SCLK Falling Edge Setup Time. Minimum SYNC High Time. 24th SCLK Falling Edge to SYNC Rising Edge. Data Setup Time. Data Hold Time. SYNC Rising Edge to BUSY Falling Edge. BUSY Pulse Width Low (Single-Channel Update.) See Table 7 Single-Channel Update Cycle Time 24th SCLK Falling Edge to LDAC Falling Edge. LDAC Pulse Width Low. BUSY Rising Edge to DAC Output Response Time. BUSY Rising Edge to LDAC Falling Edge. LDAC Falling Edge to DAC Output Response Time. DAC Output Settling Time. CLR/RESET Pulse Activation Time. RESET Pulse Width Low. RESET Time Indicated by BUSY Low. Minimum SYNC High Time in Readback Mode. SCLK Rising Edge to SDO Valid.
s max
ns min
s max
s typ/max ns max ns min s max ns min ns max
LVDS INTERFACE (Figure 6) Parameter1, 2, 3 t1 t2 t3 t4 t5 t6
1 2
Limit at TMIN, TMAX 10 4 2 2 2 2
Unit ns min ns min ns min ns min ns min ns min
Description SCLK Cycle Time. SCLK Pulse Width High and Low Time. SYNC to SCLK Setup Time. Data Setup Time. Data Hold Time. SCLK to SYNC Hold Time.
Guaranteed by design and characterization, not production tested. All input signals are specified with tr = tf = 2 ns (10% to 90% of VCC) and timed from a voltage level of 1.2 V. 3 See Figure 4 and Figure 5. 4 This is measured with the load circuit of Figure 2. 5 This is measured with the load circuit of Figure 3.
V CC
200A IOL
RL TO OUTPUT PIN
2.2k
TO OUTPUT PIN
CL
50pF 200A IOL
V OH (min) - V OL (max) 2
V OL CL 50pF
Figure 2. Load Circuit for BUSY Timing Diagram
Figure 3. Load Circuit for SDO Timing Diagram
Rev. PrF | Page 6 of 25
Preliminary Technical Data
t1
SCLK
1 2 24 1 24
AD5371
t3 t4
SYNC
t2 t6
t11
t5 t7 t8
SDI
DB23
DB0
t9
BUSY
t10
t12
LDAC1
t13 t17 t14 t15 t13
VOUT1
LDAC2
t17
VOUT2
t16
CLR
t18
VOUT
t19
RESET
VOUT
t18 t20
ACTIVE DURING BUSY. ACTIVE AFTER BUSY.
05814-004A
BUSY
1LDAC 2LDAC
Figure 4.SPI Write Timing
Rev. PrF | Page 7 of 25
Preliminary Technical Data
t22 SCLK 24 t21 48
AD5371
SYNC
SDI
DB23
DB0
DB23
DB0
INPUT WORD SPECIFIES REGISTER TO BE READ SDO
5371-0005D
NOP CONDITION
DB0
DB23
DB0
LSB FROM PREVIOUS WRITE
SELECTED REGISTER DATA CLOCKED OUT
Figure 5. SPI Read Timing
SYNC SYNC t3 SCLK SCLK SDI SDI
5371-0006
t1
t6
MSB D23
t2
t4
LSB D0
t5
Figure 6.LVDS Timing
Rev. PrF | Page 8 of 25
Preliminary Technical Data ABSOLUTE MAXIMUM RATINGS
TA = 25C, unless otherwise noted. Transient currents of up to 100 mA do not cause SCR latch-up. Table 4. Absolute Maximum Ratings
Parameter VDD to AGND VSS to AGND DVCC to DGND Digital Inputs to DGND Digital Outputs to DGND VREF1, VREF2 to AGND VOUT0-VOUT39 to AGND SIGGND to AGND AGND to DGND Operating Temperature Range (TA) Industrial (B Version) Storage Temperature Range Junction Temperature (TJ max) JA Thermal Impedance 80-LQFP 100-CSPBGA Reflow Soldering Peak Temperature Time at Peak Temperature Rating -0.3 V to +17 V -17 V to +0.3 V -0.3 V to +7 V -0.3 V to VCC + 0.3 V -0.3 V to VCC + 0.3 V -0.3 V to +7 V VSS - 0.3 V to VDD + 0.3 V 1V -0.3 V to +0.3 V -40C to +85C -65C to +150C 130C 38.72C/w 40C/w 230C 10 s to 40 s
AD5371
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only, and functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ESD 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 this product 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.
Rev. PrF | Page 9 of 25
Preliminary Technical Data
SPI/LVDS VOUT26 VOUT25 VOUT24 SYNC VOUT5 TESTO VOUT7 VOUT6 DGND DVCC DGND AGND DVCC SCLK SDO SCLK SYNC SDI SDI
AD5371
80
79
78
77
76
74
73
75
71
70
68
67
64
72
69
66
65
63
LDAC 1 CLR 2 RESET 3 BUSY 4 TESTI 5 VOUT27 6 SIGGND3 7 VOUT28 8 VOUT29 9 VOUT30 10 VOUT31 11 VOUT32 12 VOUT33 13 VOUT34 14 VOUT35 15 SIGGND4 16 VOUT36 17 VOUT37 18 VDD 19 VSS 20
190705
62
61
60 59
VOUT4 NC SIGGND0 VOUT3 VOUT2 VOUT1 VOUT0 NC VREF0 NC VREF2 VOUT23 VOUT22 VOUT21 VOUT20 VSS VDD NC NC SIGGND2
PIN 1 IDENTIFIER
58 57 56 55 54 53
AD5371
TOP VIEW (Not to Scale)
52 51 50 49 48 47 46 45 44 43 42 41
VOUT14 34
NC 35
VOUT16 37
VOUT17 38
VOUT38 25
SIGGND1 31
VOUT15 36
VOUT39 26
VOUT10 29
Figure 7.80-Lead LQFP Pin Configuration
12 11 10 9 8 7 6 SPI/ LVDS 5 4 3 2 1
VOUT12 32
VOUT19 40
VREF1 21
NC 22
NC 24
VOUT9 28
VOUT13 33
VOUT18 39
NC 23
VOUT8 27
VOUT11 30
DGND
DGND
DVCC
SYNC
SCLK
DIN
NC
LDAC
CLR
NC
AGND2
A
VOUT6
VOUT7
DVCC
SYNC
SCLK
DIN
NC
SDO
RESET
BUSY
TESTI
AGND2
B
VOUT4
VOUT5
NC
NC
NC
NC
NC
NC
NC
NC
AGND1
AGND1
C
VOUT3
SIGGND 0
NC
AGND2
AGND1
AGND1
AGND1
AGND1
AGND1
NC
VOUT25 VOUT26 D
VOUT1
VOUT2
NC
AGND2
NC
NC
NC
NC
VSS
NC
VOUT24 VOUT27 E
VOUT0
NC
NC
AGND2
NC
NC
NC
NC
VSS
NC
NC
SIGGND F 3
VREF0
NC
NC
AGND2
NC
NC
NC
NC
VSS
NC
VOUT28
NC
G
VOUT23
VREF2
NC
AGND2
NC
NC
NC
NC
VSS
NC
VOUT30 VOUT29 H
VOUT21 VOUT22
NC
VDD
VDD
VDD
VDD
VDD
VSS
NC
VOUT32 VOUT31 J
VOUT20 VOUT19
NC
NC
NC
NC
NC
NC
NC
NC
VOUT34 VOUT33 K
SIGGND 2
VDD
VOUT17 VOUT15 VOUT13 SIGGND VOUT10 1
VOUT8
VOUT38 SIGGND 4
VSS
VOUT35 L
VDD
VOUT18 VOUT16 VOUT14 VOUT12 VOUT11
VOUT9
VOUT39
VREF1
VOUT37 VOUT36
VSS
M
NC = NO CONNECT
5371-0100A
Figure 8.144-Ball Grid Array Pin Configuration - Bottom View
Rev. PrF | Page 10 of 25
Preliminary Technical Data
Table 5. Pin Function Descriptions
Pin DVCC VSS VDD AGND DGND VREF0 VREF1 VREF2 VOUT0 to VOUT39 SYNC SCLK SDI SDO SYNC SCLK SDI CLR SPI/LVDS LDAC BUSY RESET SIGGND0 SIGGND1 SIGGND1 SIGGND3 SIGGND4 TESTI TESTO
AD5371
Function Logic Power Supply; 2.5 V to 5.5 V. These pins should be decoupled with 0.1 F ceramic capacitors and 10 F capacitors. Negative Analog Power Supply; -4.5 V to -16.5 V for specified performance. These pins should be decoupled with 0.1 F ceramic capacitors and 10 F capacitors. Positive Analog Power Supply; +8 V to +16.5 V for specified performance. These pins should be decoupled with 0.1 F ceramic capacitors and 10 F capacitors. Ground for All Analog Circuitry. All AGND pins should be connected to the AGND plane. Ground for All Digital Circuitry. All DGND pins should be connected to the DGND plane. Reference Input for DACs 0 to 7. This reference voltage is referred to AGND. Reference Input for DACs 8 to 15. reference This voltage is referred to AGND. Reference Input for DACs 16 to 39. This reference voltage is referred to AGND. DAC Outputs. Buffered analog outputs for each of the 40 DAC channels. Each analog output is capable of driving an output load of 10 k to ground. Typical output impedance of these amplifiers is 0.5 . Active Low or Differential SYNC Input (Complement) for SPI or LVDS Interface. This is the frame synchronization signal for the SPI or LVDS serial interface. See SPI and LVDS timing diagrams and descriptions for more details. Serial Clock Input for SPI or LVDS Interface. See SPI and LVDS timing diagrams and descriptions for more details. Serial Data Input for SPI or LVDS Interface. See SPI and LVDS timing diagrams and descriptions for more details. Serial Data Output for SPI Interface. CMOS output. SDO can be used for readback. Data is clocked out on SDO on the rising edge of SCLK and is valid on the falling edge of SCLK. Differential SYNC Input for LVDS Interface . This is the frame synchronization signal for the LVDS serial interface. See LVDS timing diagram and description for more details. Differential Serial Clock Input (Complement) for LVDS Interface. See LVDS timing diagrams and descriptions for more details. Differential Serial Data Input (Complement) for LVDS Interface. See LVDS timing diagrams and descriptions for more details. Asynchronous Clear Input (level sensitive, active low). See the Clear Function section for more information Selects between SPI (low) or LVDS (high) serial interface. Load DAC Logic Input (active low). See the BUSY AND LDAC FUNCTIONS section for more information Digital Input/Open-Drain Output. BUSY is open-drain when an output. See the BUSY AND LDAC FUNCTIONS section for more information Asynchronous Digital Reset Input. Reference Ground for DACs 0 to 7. VOUT0 to VOUT7 are referenced to this voltage. Reference Ground for DACs 8 to 15. VOUT8 to VOUT15 are referenced to this voltage. Reference Ground for DACs 16 to 23. VOUT16 to VOUT23 are referenced to this voltage. Reference Ground for DACs 24 and 31. VOUT24 to VOUT31 are referenced to this voltage. Reference Ground for DACs 32 to 39. VOUT32 to VOUT39 are referenced to this voltage. Test Input Pin. This pin should be connected to DGND Test Output Pin. This pin should be left unconnected
Rev. PrF | Page 11 of 25
Preliminary Technical Data TERMINOLOGY
Relative Accuracy Relative accuracy, or endpoint linearity, is a measure of the maximum deviation from a straight line passing through the endpoints of the DAC transfer function. It is measured after adjusting for zero-scale error and full-scale error and is expressed in least significant bits (LSB). Differential Nonlinearity Differential nonlinearity is the difference between the measured change and the ideal 1 LSB change between any two adjacent codes. A specified differential nonlinearity of 1 LSB maximum ensures monotonicity. Zero-Scale Error Zero-scale error is the error in the DAC output voltage when all 0s are loaded into the DAC register. Zero-scale error is a measure of the difference between VOUT (actual) and VOUT (ideal) expressed in mV. Zero-scale error is mainly due to offsets in the output amplifier. Full-Scale Error Full-scale error is the error in DAC output voltage when all 1s are loaded into the DAC register. Full-scale error is a measure of the difference between VOUT (actual) and VOUT (ideal) expressed in mV. It does not include zero-scale error. Gain Error Gain error is the difference between full-scale error and zero-scale error. It is expressed in mV. Gain Error = Full-Scale Error - Zero-Scale Error VOUT Temperature Coefficient This includes output error contributions from linearity, offset, and gain drift. DC Output Impedance DC output impedance is the effective output source resistance. It is dominated by package lead resistance.
AD5371
DC Crosstalk The DAC outputs are buffered by op amps that share common VDD and VSS power supplies. If the dc load current changes in one channel (due to an update), this can result in a further dc change in one or more channel outputs. This effect is more significant at high load currents and reduces as the load currents are reduced. With high impedance loads, the effect is virtually immeasurable. Multiple VDD and VSS terminals are provided to minimize dc crosstalk. Output Voltage Settling Time The amount of time it takes for the output of a DAC to settle to a specified level for a full-scale input change. Digital-to-Analog Glitch Energy The amount of energy injected into the analog output at the major code transition. It is specified as the area of the glitch in nV-s. It is measured by toggling the DAC register data between 0x1FFF and 0x2000. Channel-to-Channel Isolation Channel-to-channel isolation refers to the proportion of input signal from one DAC's reference input that appears at the output of another DAC operating from another reference. It is expressed in dB and measured at midscale. DAC-to-DAC Crosstalk DAC-to-DAC crosstalk is the glitch impulse that appears at the output of one converter due to both the digital change and subsequent analog output change at another converter. It is specified in nV-s. Digital Crosstalk The glitch impulse transferred to the output of one converter due to a change in the DAC register code of another converter is defined as the digital crosstalk and is specified in nV-s. Digital Feedthrough When the device is not selected, high frequency logic activity on the device's digital inputs can be capacitively coupled both across and through the device to show up as noise on the VOUT pins. It can also be coupled along the supply and ground lines. This noise is digital feedthrough. Output Noise Spectral Density Output noise spectral density is a measure of internally generated random noise. Random noise is characterized as a spectral density (voltage per Hz). It is measured by loading all DACs to midscale and measuring noise at the output. It is measured in nV/(Hz)
1/2
Rev. PrF | Page 12 of 25
Preliminary Technical Data FUNCTIONAL DESCRIPTION
DAC ARCHITECTURE--GENERAL
The AD5371 contains 40 DAC channels and 40 output amplifiers in a single package. The architecture of a single DAC channel consists of a 14-bit resistor-string DAC followed by an output buffer amplifier. The resistor-string section is simply a string of resistors, each of value R, from VREF to AGND. This type of architecture guarantees DAC monotonicity. The 14-bit binary digital code loaded to the DAC register determines at which node on the string the voltage is tapped off before being fed into the output amplifier. The output amplifier multiplies Table 6. AD5371 Registers
Register Name X1A (group)(channel) X1B (group) (channel) M (group) (channel) C (group) (channel) X2A (group)(channel) Word Length (Bits) 14 14 14 14 14 Description Input data register A, one for each DAC channel. Input data register B, one for each DAC channel. Gain trim registers, one for each DAC channel. Offset trim registers, one for each DAC channel.
AD5371
the DAC out voltage by 4. The output span is 12 V with a 3 V reference and 20 V with a 5 V reference.
CHANNEL GROUPS
The 40 DAC channels of the AD5371 are arranged into five groups of 8 channels. The eight DACs of Group 0 derive their reference voltage from VREF0, those of Group 1 from VREF1, while the remaining groups derive their reference voltage from VREF2. Each group has its own signal ground pin.
Output data register A, one for each DAC channel. These registers store the final, calibrated DAC data after gain and offset trimming. They are not readable, nor directly writable. Output data register B, one for each DAC channel. These registers store the final, calibrated DAC data after gain and offset trimming. They are not readable, nor directly writable. Data registers from which the DACs take their final input data. The DAC registers are updated from the X2A or X2B registers. They are not readable, nor directly writable.
X2B (group) (channel)
14
DAC (group) (channel) OFS0 OFS1 OFS2 Control 14 14 14 3
Offset DAC 0 data register, sets offset for Group 0. Offset DAC 1 data register, sets offset for Group 1. Offset DAC 2 data register, sets offset for Groups 2 to 4. Bit 2 = A/B. 0 = global selection of X1A input data registers. 1 = X1B registers. Bit 1 = Enable Temp Shutdown. 0 = disable temp shutdown. 1 = enable. Bit 0 = Soft Power Down. 0 = soft power up. 1 = soft power down.
A/B Select 0
8
Each bit in this register determines if a DAC in Group 0 takes its data from register X2A or X2B (0 = X2A, 1 = X2B)
A/B Select 1 A/B Select 2 A/B Select 3 A/B Select 4
8 8 8 8
Each bit in this register determines if a DAC in Group 1 takes its data from register X2A or X2B (0 = X2A, 1 = X2B) Each bit in this register determines if a DAC in Group 2 takes its data from register X2A or X2B (0 = X2A, 1 = X2B) Each bit in this register determines if a DAC in Group 3 takes its data from register X2A or X2B (0 = X2A, 1 = X2B) Each bit in this register determines if a DAC in Group 4 takes its data from register X2A or X2B (0 = X2A, 1 = X2B)
Rev. PrF | Page 13 of 25
Preliminary Technical Data
A/ B REGISTERS AND GAIN/OFFSET ADJUSTMENT
Each DAC channel has seven data registers. The actual DAC data word can be written to either the X1A or X1B input register, depending on the setting of the A/B bit in the Control Register. If the A/B bit is 0, data will be written to the X1A register. If the A/B bit is 1, data will be written to the X1B register. Note that this single bit is a global control and affects every DAC channel in the device. It is not possible to set up the device on a per-channel basis so that some writes are to X1A registers and some writes are to X1B registers.
X1A REGISTER MUX X1B REGISTER M REGISTER C REGISTER X2B REGISTER X2A REGISTER MUX
AD5371
LOAD DAC
All DACs in the AD5371 can be updated simultaneously by taking LDAC low, when each DAC register will be updated from either its X2A or X2B register, depending on the setting of the A/B select registers. The DAC register is not readable, nor directly writable by the user.
OFFSET DACS
In addition to the gain and offset trim for each DAC, there are three 14-bit Offset DACs, one for Group 0, one for group 1, and one for groups 2 to 4. These allow the output range of all DACs connected to them to be offset within a defined range. Thus, subject to the limitations of headroom, it is possible to set the output range of Group 0, Group 1 or Groups 2 to 4 to be unipolar positive, unipolar negative, or bipolar, either symmetrical or asymmetrical about zero volts. The DACs in the AD5371 are factory trimmed with the Offset DACs set at their default values. This gives the best offset and gain performance for the default output range and span. When the output range is adjusted by changing the value of the Offset DAC an extra offset is introduced due to the gain error of the Offset DAC. The amount of offset is dependent on the magnitude of the reference and how much the Offset DAC moves from its default value. This offset is quoted on the specification page. The worst case offset occurs when the Offset DAC is at positive or negative full-scale. This value can be added to the offset present in the main DAC of a channel to give an indication of the overall offset for that channel. In most cases the offset can be removed by programming the channels C register with an appropriate value. The extra offset cause by the Offset DACs only needs to be taken into account when the Offset DAC is changed from its default value. Figure 10 shows the allowable code range which may be loaded to the Offset DAC and this is dependant on the reference value used. Thus, for a 5V reference, the Offset DAC should not be programmed with a value greater than 8192 (0x2000).
5 RESERVED
DAC REGISTER
DAC
Figure 9. Data Registers Associated With Each DAC Channel
Each DAC channel also has a gain (M) and offset (C) register, which allow trimming out of the gain and offset errors of the entire signal chain. Data from the X1A register is operated on by a digital multiplier and adder controlled by the contents of the M and C registers. The calibrated DAC data is then stored in the X2A register. Similarly, data from the X1B register is operated on by the multiplier and adder and stored in the X2B register. Although a multiplier and adder symbol are shown for each channel, there is only one multiplier and one adder in the device, which are shared between all channels. This has implications for the update speed when several channels are updated at once, as described later. Each time data is written to the X1A register, or to the M or C register with the A/B control bit set to 0, the X2A data is recalculated and the X2A register is automatically updated. Similarly, X2B is updated each time data is written to X1B, or to M or C with A/B set to 1. The X2A and X2B registers are not readable, nor directly writable by the user. Data output from the X2A and X2B registers is routed to the final DAC register by a multiplexer. Whether each individual DAC takes its data from the X2A or X2B register is controlled by an 8-bit A/B Select Register associated with each group of 8 DACs. If a bit in this register is 0, the DAC takes its data from the X2A register; if 1 the DAC takes its data from the X2B register (bit 0 controls DAC 0 through bit 7 controls DAC 7). Note that, since there are 40 bits in 5 registers, it is possible to set up, on a per-channel basis, whether each DAC takes its data from the X2A or X2B register. A global command is also provided that sets all bits in the A/B Select Registers to 0 or to 1.
4
VREF (V)
3
2
0 0
4096
8192 12288 OFFSET DAC CODE
16383
Figure 10. Offset DAC Code Range
Rev. PrF | Page 14 of 25
5370-0200
1
Preliminary Technical Data
OUTPUT AMPLIFIER
As the output amplifiers can swing to 1.4 V below the positive supply and 1.4 V above the negative supply, this limits how much the output can be offset for a given reference voltage. For example, it is not possible to have a unipolar output range of 20V, since the maximum supply voltage is 16.5 V.
AD5371
multiplied by 4 in the transfer function as this DAC is a 14 bit device. On power up the default code loaded to the offset DAC is 5461 (0x1555). With a 3V reference this gives a span of -4 V to +8 V.
REFERENCE SELECTION
The AD5371 has three reference input pins. The voltage applied to the reference pins determines the output voltage span on VOUT0 to VOUT31. VREF0 determines the voltage span for VOUT0 to VOUT7 (Group 0) and VREF1 determines the voltage span for VOUT8 to VOUT15 (Group 1) and VREF2 determines the voltage span for VOUT16 to VOUT31 (Group 2 to Group 3). The reference voltage applied to each VREF pin can be different, if required, allowing the groups to have a different voltage spans. The output voltage range and span can be adjusted further by programming the offset and gain registers for each channel as well as programming the offset DACs. If the offset and gain features are not used (i.e. the m and c registers are left at their default values) the required reference levels can be calculated as follows: VREF = (VOUTmax - VOUTmin)/4 If the offset and gain features of the AD5371 are used, then the required output range is slightly different. The chosen output range should take into account the system offset and gain errors that need to be trimmed out. Therefore, the chosen output range should be larger than the actual, required range. The required reference levels can be calculated as follows: 1. 2. 3. Identify the nominal output range on VOUT. Identify the maximum offset span and the maximum gain required on the full output signal range. Calculate the new maximum output range on VOUT including the expected maximum offset and gain errors. Choose the new required VOUTmax and VOUTmin, keeping the VOUT limits centered on the nominal values. Note that VDD and VSS must provide sufficient headroom. Calculate the value of VREF as follows: VREF = (VOUTMAX - VOUTMIN)/4
DAC CHANNEL S2
S1
OUTPUT R6 10k CLR
CLR R5 R1 R3 R2 CLR
S3 R4 SIGGND OFFSET DAC
2049-0008
SIGGND CHECK VALUE OF R1 &R5 R1,R2,R3 = 20k R4,R5 = 60k R6 = 10k
Figure 11. Output Amplifier and Offset DAC
Figure 11 shows details of a DAC output amplifier and its connections to the Offset DAC. On power up, S1 is open, disconnecting the amplifier from the output. S3 is closed, so the output is pulled to SIGGND (R1 and R2 are very much greater than R6). S2 is also closed to prevent the output amplifier being open-loop. If CLR is low at power-up, the output will remain in this condition until CLR is taken high. The DAC registers can be programmed, and the outputs will assume the programmed values when CLR is taken high. Even if CLR is high at powerup, the output will remain in the above condition until VDD > 6 V and VSS < -4 V and the initialization sequence has finished. The outputs will then go to their power-on default value.
TRANSFER FUNCTION
From the previous text, it can be seen that the output voltage of a DAC in the AD5371 depends on the value in the input register, the value of the M and C registers, and the offset from the Offset DAC. The transfer function is given by: Code applied to DAC from X1A or X1B register:DAC_CODE = INPUT_CODE x (m+1)/214 + c - 213 DAC output voltage:VOUT = 4 x VREF x (DAC_CODE - OFFSET_CODE )/214 +VSIGGND Notes DAC_CODE should be within the range of 0 to 16383. For 12 V span VREF = 3.0 V. For 20 V span VREF = 5.0 V. X1A, X1B default code = 5461 m = code in gain register - default code = 214 - 1. c = code in offset register - default code = 213. OFFSET_CODE is the code loaded to the offset DAC. It is 5. 4.
Reference Selection Example
Nominal Output Range = 12V (-4V to +8V) Offset Error = 70mV Gain Error = 3% SIGGND = AGND = 0V 1) Gain Error = 3% => Maximum Positive Gain Error = +3% => Output Range incl. Gain Error = 12 + 0.03(12)=12.36V
Rev. PrF | Page 15 of 25
Preliminary Technical Data
2) Offset Error = 70mV => Maximum Offset Error Span = 2(70mV)=0.14V => Output Range including Gain Error and Offset Error = 12.36V + 0.14V = 12.5V VREF Calculation Actual Output Range = 12.5V, that is -4.25V to +8.25V (centered); VREF = (8.25V + 4.25V)/4 = 3.125V
AD5371
3) 41 LSBs should be added to the default c register value: (8192 + 41) = 8151 4) 8151 should be programmed to the c register The gain error can now be removed. The output is set to +8V and a value of +8.02V is measured. This is a gain error of +20mV 1) 20mV = 27 LSBs 2) 27 LSBs should be subtracted from the default m register value: (16383-27) = 16356. 3) 16356 should be programmed to the m register
3)
If the solution yields an inconvenient reference level, the user can adopt one of the following approaches: 1. 2. Use a resistor divider to divide down a convenient, higher reference level to the required level. Select a convenient reference level above VREF and modify the Gain and Offset registers to digitally downsize the reference. In this way the user can use almost any convenient reference level but may reduce the performance by overcompaction of the transfer function. Use a combination of these two approaches
RESET FUNCTION
When the RESET pin is taken low, the DAC buffers are disconnected and the DAC outputs VOUT0 to VOUT39 are tied to their associated SIGGND signals via a 10 k resistor. On the rising edge of RESET the AD5371 state machine initiates a reset sequence to reset the X, M and C registers to their default values. This sequence typically takes 300s and the user should not write to the part during this time. When the reset sequence is complete, and provided that CLR is high, the DAC output will be at a potential specified by the default register settings which will be equivalent to SIGGGND. The DAC outputs will remain at SIGGND until the X, M or C registers are updated and LDAC is taken low.
3.
CALIBRATION
The user can perform a system calibration on the AD5371 to reduce gain and offset errors to below 1 LSB. This is achieved by calculating new values for the m and c registers and reprogramming them.
CLEAR FUNCTION
CLR is an active low input which should be high for normal operation. The CLR pin has in internal 500k pull-down resistor. When CLR is low, the input to each of the DAC output buffer stages, VOUT0 to VOUT39, is switched to the externally set potential on the relevant SIGGND pin. While CLR is low, all LDAC pulses are ignored. When CLR is taken high again, the DAC outputs remain cleared until LDAC is taken low. The contents of input registers and DAC registers 0 to 39 are not affected by taking CLR low. To prevent glitches appearing on the outputs CLR should be brought low whenever the output span is adjusted by writing to the offset DAC.
Reducing Offset and Gain Error
Offset Error is reduced as follows: 1. Set the output to the lowest possible value. 2. Measure the actual output voltage and compare it to the required value. This gives the offset error. 3. Calculate the number of LSBs equivalent to the offset error and add or subtract this from the default value of the c register. Gain Error is reduced as follows: 1. Reduce the offset error. 2. Set the output to the highest possible value 3. Measure the actual output voltage and compare it to the required value. This gives the gain error. 4. Calculate the number of LSBs equivalent to the gain error and subtract it from the default value of the m register. Note that only positive gain error can be reduced.
BUSY AND LDAC FUNCTIONS
The value of an X2 (A or B) register is calculated each time the user writes new data to the corresponding X1, C, or M registers. During the calculation of X2, the BUSY output goes low. While BUSY is low, the user can continue writing new data to the X1, M, or C registers (see the Register Update Rates section for more details), but no DAC output updates can take place. The DAC outputs are updated by taking the LDAC input low. If LDAC goes low while BUSY is active, the LDAC event is stored and the DAC outputs update immediately after BUSY goes high. A user can also hold the LDAC input permanently low. In this case, the DAC outputs update immediately after BUSY
CALIBRATION EXAMPLE
This example assumes that a -4V to +8V output is required. The DAC output is set to -4V but is measured at -4.03V. This gives an offset of -30mV. 1) 1 LSB = 12V/16384 = 732.42V 2) 30mV = 41 LSBs
Rev. PrF | Page 16 of 25
Preliminary Technical Data
goes high. BUSY also goes low, for approximately 500ns, whenever the A/B Select Registers are written to. The BUSY pin is bidirectional and has a 50 k internal pullup resistor. Where multiple AD5371 devices may be used in one system the BUSY pins can be tied together. This is useful where it is required that no DAC in any device is updated until all other DACs are ready. When each device has finished updating the X2 (A or B) registers it will release the BUSY pin. If another device hasn't finished updating its X2 registers it will hold BUSY low, thus delaying the effect of LDAC going low. The DAC outputs are updated by taking the LDAC input low. If LDAC goes low while BUSY is active, the LDAC event is stored and the DAC outputs update immediately after BUSY goes high. A user can also hold the LDAC input permanently low. In this case, the DAC outputs update immediately after BUSY goes high. As described later, the AD5371 has flexible addressing that allows writing of data to a single channel, all channels in a group, the same channel in groups 0 to 4 or groups 1 to 4, or all channels in the device. This means that 1, 5, 8 or 40 X2 register values may need to be calculated and updated. As there is only one multiplier shared between 40 channels, this task must be done sequentially, so the length of the BUSY pulse will vary according to the number of channels being updated. Table 7. BUSY Pulse Widths
Action Loading X1A, X1B, C, or M to 1 channel Loading X1A, X1B, C, or M to 5 channels Loading X1A, X1B, C, or M to 8 channels Loading X1A, X1B, C, or M to 40 channels BUSY Pulse Width (s max) 1.25 3.25 4.75 20.75
AD5371
THERMAL MONITOR FUNCTION
The AD5371 can be programmed to power down the DACs if the temperature on the die exceeds 130C. Setting Bit 1 in the control register (see Table 12) will enable this function. If the die temperature exceeds 130C the AD5371 will enter a temperature power-down mode, which is equivalent to setting the power-down bit in the control register. To indicate that the AD5371 has entered temperature shutdown mode Bit 4 of the control register is set. The AD5371 will remain in temperature shutdown mode, even if the die temperature falls, until Bit 1 in the control register is cleared.
TOGGLE MODE
The AD5371 has two X2 registers per channel, X2A and X2B, which can be used to switch the DAC output between two levels with ease. This approach greatly reduces the overhead required by a micro-processor which would otherwise have to write to each channel individually. When the user writes to either the X1A ,X2A, M or C registers the calculation engine will take a certain amount of time to calculate the appropriate X2A or X2B values. If the application only requires that the DAC output switch between two levels, such as a data generator, any method which reduces the amount of calculation time encountered is advantageous. For the data generator example the user need only set the high and low levels for each channel once, by writing to the X1A and X1B registers. The values of X2A and X2B will be calculated and stored in their respective registers. The calculation delay therefore only happens during the setup phase, i.e. when programming the initial values. To toggle a DAC output between the two levels it is only required to write to the relevant A/B Select Register to set the MUX2 register bit. Furthermore, since there are 8 MUX2 control bits per register it is possible to update eight channels with a single write. Table 14 shows the bits that correspond to each DAC output.
BUSY Pulse Width = ((Number of Channels +1) x 500ns) +250ns
The AD5371 contains an extra feature whereby a DAC register is not updated unless its X2A or X2B register has been written to since the last time LDAC was brought low. Normally, when LDAC is brought low, the DAC registers are filled with the contents of the X2A or X2B registers, depending on the setting of the A/B Select Registers. However the AD5371 updates the DAC register only if the X2 data has changed, thereby removing unnecessary digital crosstalk.
POWER-DOWN MODE
The AD5371 can be powered down by setting Bit 0 in the control register. This will turn off the DACs thus reducing the current consumption. The DAC outputs will be connected to their respective SIGGND potentials. The power-down mode doesn't change the contents of the registers and the DACs will return to their previous voltage when the power-down bit is cleared.
Rev. PrF | Page 17 of 25
Preliminary Technical Data SERIAL INTERFACE
The AD5371 contains two high-speed serial interfaces, an SPIcompatible, interface operating at clock frequencies up to 50MHz (20MHz for read operations), and an LVDS interface. To minimize both the power consumption of the device and on-chip digital noise, the interface powers up fully only when the device is being written to, that is, on the falling edge of SYNC.
AD5371
SPI WRITE MODE
The AD5371 allows writing of data via the serial interface to every register directly accessible to the serial interface, which is all registers except the X2A and X2B registers and the DAC registers. The X2A and X2B registers are updated when writing to the X1A, X1B, M and C registers, and the DAC registers are updated by LDAC. The serial word (see Table 8) is 24 bits long. 14 of these bits are data bits, six bits are address bits, and two bits are mode bits that determine what is done with the data. Two bits are reserved. The serial interface works with both a continuous and a burst (gated) serial clock. Serial data applied to SDI is clocked into the AD5371 by clock pulses applied to SCLK. The first falling edge of SYNC starts the write cycle. At least 24 falling clock edges must be applied to SCLK to clock in 24 bits of data, before SYNC is taken high again. If SYNC is taken high before the 24th falling clock edge, the write operation will be aborted. If a continuous clock is used, SYNC must be taken high before the 25th falling clock edge. This inhibits the clock within the AD5371. If more than 24 falling clock edges are applied before SYNC is taken high again, the input data will be corrupted. If an externally gated clock of exactly 24 pulses is used, SYNC may be taken high any time after the 24th falling clock edge. The input register addressed is updated on the rising edge of SYNC. In order for another serial transfer to take place, SYNC must be taken low again.
SPI INTERFACE
The serial interface is 2.5 V LVTTL compatible when operating from a 2.7 V to 3.6 V DVCC supply. The SPI interface is selected when the SPI/LVDS pin is held low.It is controlled by four pins, as follows.
SYNC
Frame synchronization input.
SDI
Serial data input pin.
SCLK
Clocks data in and out of the device.
SDO
Serial data output pin for data readback. When the SPI mode is used the SYNC, SDI and SCLK pins should be connected to DGND either directly or by using pulldown resistors.
LVDS INTERFACE
The LVDS interface is selected when the SPI/LVDS pin is held high. The LVDS interface uses the same input pins as the SPI interface with the same designations. SDO is not used. In addition, three other pins are provided for the complementary signals needed for differential operation, thus: SYNC/SYNC Differential frame synchronization signal. SDI/SDI Differential serial data input. SCLK/SCLK Differential clock input. Table 8. Serial Word Bit Assignation
I23 M1 I22 M0 I21 A5 I20 A4 I19 A3 I18 A2 I17 A1 I16 A0 I15 D13 I14 D12 I13 D11 I12 D10 I11 D9
I10 D8
I9 D7
I8 D6
I7 D5
I6 D4
I5 D3
I4 D2
I3 D1
I2 D0
I1* 0
I0* 0
*Bits I1 and I0 are reserved for future use. Set to 0 when writing. Read back as 0.
Rev. PrF | Page 18 of 25
Preliminary Technical Data
SPI READBACK MODE
The AD5371 allows data readback via the serial interface from every register directly accessible to the serial interface, which is all registers except the X2A, X2B and DAC registers. In order to read back a register, it is first necessary to tell the AD5371 which register is to be read. This is achieved by writing to the device a word whose first two bits are the special function code 00. The remaining bits then determine if the operation is a readback, and the register which is to be read back, or if it is a write to of the special function registers such as the control register. After the special function write has been performed, if it is a readback command then data from the selected register will be clocked out of the SDO pin during the next SPI operation. The SDO pin is normally three-state but becomes driven as soon as a read command has been issued. The pin will remain driven until the registers data has been clocked out. Figure 5 for the read timing diagram. Note that due to the timing requirements of t5 (25ns) the maximum speed of the SPI interface during a read operation should not exceed 20MHz.
AD5371
REGISTER UPDATE RATES
As mentioned previously the value of the X2 (A or B) register is calculated each time the user writes new data to the corresponding X1, C or M registers. The calculation is performed by a three stage process. The first two stages take 500ns each and the third stage takes 250ns. When the write to one of the X1, C or M registers is complete the calculation process begins. If the write operation involves the update of a single DAC channel the user is free to write to another register provided that the write operation doesn't finish until the first stage calculation is complete, i.e. 500ns after the completion of the first write operation. If a group of channels is being updated by a single write operation the first stage calculation will be repeated for each channel, taking 500ns per channel. In this case the user should not complete the next write operation until this time has elapsed.
CHANNEL ADDRESSING AND SPECIAL MODES
If the mode bits are not 00, then the data word D13 to D0 is written to the device. Address bits A5 to A0 determine which channel or channels is/are written to, while the mode bits determine to which register (X1A, X1B, C or M) the data is written, as shown in Table 8. If data is to be written to the X1A or X1B register, the setting of the A/B bit in the Control Register determines which (0 X1A, 1 X1B). Table 9. Mode Bits
M1 1 1 0 0 M0 1 0 1 0 Action Write DAC input data (X1A or X1B) register, depending on Control Register A/B bit. Write DAC offset (C) register Write DAC gain (M) register Special function, used in combination with other bits of word
LVDS OPERATION
The LVDS interface operates as follows (note that, since the LVDS signals are differential, when a signal goes high its complementary signal goes low, and vice versa). The SYNC signal frames the data. SCLK is initially high. After SYNC goes low and the SYNC to SCLK setup time has elapsed, SCLK can start to clock in the data. Data is clocked into the AD5371 on the high to low transition of SCLK and must be stable at this time (observe setup and hold time specs). SYNC may then be taken high after the SCLK to SYNC hold time to latch the data. The same comments about burst and continuous clocks apply to the LVDS interface as to the SPI interface. Readback is not available when using the LVDS interface.
The AD5371 has very flexible addressing that allows writing of data to a single channel, all channels in a group, the same channel in groups 0 to 4 or groups 1 to 4, or all channels in the device Table 10 shows all these address modes.
Rev. PrF | Page 19 of 25
Preliminary Technical Data
Table 10. Group and Channel Addressing This table shows which group(s) and which channel(s) is/are addressed for every combination of address bits A5 to A0.
ADDRESS BITS A5 TO A3
000 000 001 010 011 100 101 110 111 All groups, all channels Group 0, all channels Group 1, all channels Group 2, all channels Group 3, all channels Group 4, all channels Reserved Reserved 001 Group 0, channel 0 Group 0, channel 1 Group 0, channel 2 Group 0, channel 3 Group 0, channel 4 Group 0, channel 5 Group 0, channel 6 Group 0, channel 7 010 Group 1, channel 0 Group 1, channel 1 Group 1, channel 2 Group 1, channel 3 Group 1, channel 4 Group 1, channel 5 Group 1, channel 6 Group 1, channel 7 011 Group 2, channel 0 Group 2, channel 1 Group 2, channel 2 Group 2, channel 3 Group 2, channel 4 Group 2, channel 5 Group 2, channel 6 Group 2, channel 7 100 Group 3, channel 0 Group 3, channel 1 Group 3, channel 2 Group 3, channel 3 Group 3, channel 4 Group 3, channel 5 Group 3, channel 6 Group 3, channel 7 101 Group 4, channel 0 Group 4, channel 1 Group 4, channel 2 Group 4, channel 3 Group 4, channel 4 Group 4, channel 5 Group 4, channel 6 Group 4, channel 7 110 Groups 0,1,2,3,4 channel 0 Groups 0,1,2,3,4 channel 1 Groups 0,1,2,3,4 channel 2 Groups 0,1,2,3,4 channel 3 Groups 0,1,2,3,4 channel 4 Groups 0,1,2,3,4 channel 5 Groups 0,1,2,3,4 channel 6 Groups 0,1,2,3,4 channel 7
AD5371
111 Groups 1,2,3,4 channel 0 Groups 1,2,3,4 channel 1 Groups 1,2,3,4 channel 2 Groups 1,2,3,4 channel 3 Groups 1,2,3,4 channel 4 Groups 1,2,3,4 channel 5 Groups 1,2,3,4 channel 6 Groups 1,2,3,4 channel 7
ADDRESS BITS A2 TO A0
SPECIAL FUNCTION MODE
If the mode bits are 00, then the special function mode is selected, as shown in Table 11. Bits I21 to I16 of the serial data word select the special function, while the remaining bits are Table 11. Special Function Mode
I23 0 I22 0 I21 S5 I20 S4 I19 S3 I18 S2 I17 S1 I16 S0 I15 F15 I14 F14 I13 F13 I12 F12 I11 F11
data required for execution of the special function, for example the channel address for data readback. The codes for the special functions are shown in Table 12. Table 13 shows the addresses for data readback.
I10 F10
I9 F9
I8 F8
I7 F7
I6 F6
I5 F5
I4 F4
I3 F3
I2 F2
I1 F1
I0 F0
Rev. PrF | Page 20 of 25
Preliminary Technical Data
Table 12. Special Function Codes
SPECIAL FUNCTION CODE S5 0 0 S4 0 0 S3 0 0 S2 0 0 S1 0 0 S0 0 1 DATA F15-F0 0000 0000 0000 0000 XXXX XXXX XXXX X[F2:F0] NOP ACTION
AD5371
Write control register F2 = 1 Select B reg for input; F2 = 0 Select A reg for input F1 = 1 En temp shutdown; F1 = 0 Disable temp shutdown F0 = 1 Soft power down; F0 = 0 soft power up Write data in F13:F0 to OFS0 register Write data in F13:F0 to OFS1 register Write data in F13:F0 to OFS2 register Select register for readback Write data in F7:F0 to A/B Select Register 0 Write data in F7:F0 to A/B Select Register 1 Write data in F7:F0 to A/B Select Register 2 Write data in F7:F0 to A/B Select Register 3 Write data in F7:F0 to A/B Select Register 4 Block write A/B Select Registers F7:F0 = 0, write all 0's (all channels use X2A register) F7:F0 = 1, wrote all 1's (all channels use X2B register)
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 1 1 1
0 0 1 1 1 1 0 0 0 0
1 1 0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1 0 1
XX[F13:F0] XX[F13:F0] XX[F13:F0] See Table 13 XXXX XXXX[F7:F0] XXXX XXXX[F7:F0] XXXX XXXX[F7:F0] XXXX XXXX[F7:F0] XXXX XXXX[F7:F0] XXXX XXXX[F7:F0]
Table 13. Address Codes for Data Readback
F15 0 0 0 0 1 1 1 1 1 1 1 1 1 F14 0 0 1 1 0 0 0 0 0 0 0 0 0 F13 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 1 1 1 0 0 0 0 1 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 0 Bits F12 to F7 select channel to be read back, from Channel 0 = 001000 to Channel 39 = 101111 F12 F11 F10 F9 F8 F7 REGISTER READ A Register B Register C Register M Register Control Register OFS0 Data Register OFS1 Data Register OFS2 Data Register A/B Select Register 0 A/B Select Register 1 A/B Select Register 2 A/B Select Register 3 A/B Select Register 4
Note: F6 to F0 are don't care for data readback function.
Rev. PrF | Page 21 of 25
Preliminary Technical Data
Table 14. DACs Select by A/B Select Registers
A/B Select Register 0 1 2 3 4 Bits F7 VOUT7 VOUT15 VOUT23 VOUT31 VOUT39 F6 VOUT6 VOUT14 VOUT22 VOUT30 VOUT38 F5 VOUT5 VOUT13 VOUT21 VOUT29 VOUT37 F4 VOUT4 VOUT12 VOUT20 VOUT28 VOUT36 F3 VOUT3 VOUT11 VOUT19 VOUT27 VOUT35 F2 VOUT2 VOUT10 VOUT18 VOUT26 VOUT34 F1 VOUT1 VOUT9 VOUT17 VOUT25 VOUT33 F0 VOUT0 VOUT8 VOUT16 VOUT24 VOUT32
AD5371
POWER SUPPLY DECOUPLING
In any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated performance. The printed circuit board on which the AD5371 is mounted should be designed so that the analog and digital sections are separated and confined to certain areas of the board. If the AD5371 is in a system where multiple devices require an AGND-to-DGND connection, the connection should be made at one point only. The star ground point should be established as close as possible to the device. For supplies with multiple pins (VSS, VDD, VCC), it is recommended to tie these pins together and to decouple each supply once. The AD5371 should have ample supply decoupling of 10 F in parallel with 0.1 F on each supply located as close to the package as possible, ideally right up against the device. The 10 F capacitors are the tantalum bead type. The 0.1 F capacitor should have low effective series resistance (ESR) and effective series inductance (ESI), such as the common ceramic types that provide a low impedance path to ground at high frequent cies, to handle transient currents due to internal logic switching. Digital lines running under the device should be avoided, because these couple noise onto the device. The analog ground plane should be allowed to run under the AD5371 to avoid noise coupling. The power supply lines of the AD5371 should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. Fast switching digital signals should be shielded with digital ground to avoid radiating noise to other parts of the board, and should never be run near the reference inputs. It is essential to minimize noise on all VREF lines. Avoid crossover of digital and analog signals. Traces on opposite sides of the board should run at right angles to each other. This reduces the effects of feedthrough through the board. A microstrip technique is by far the best, but not always possible with a double-sided board. In this technique, the
component side of the board is dedicated to ground plane, while signal traces are placed on the solder side. As is the case for all thin packages, care must be taken to avoid flexing the package and to avoid a point load on the surface of this package during the assembly process.
POWER SUPPLY SEQUENCING
When the supplies are connected to the AD5371 it is important that the AGND and DGND pins are connected to the relevant ground plane before the positive or negative supplies are applied. In most applications this is not an issue as the ground pins for the power supplies will be connected to the ground pins of the AD5371 via ground planes. Where the AD5371 is to be used in a hot-swap card care should be taken to ensure that the ground pins are connected to the supply grounds before the positive or negative supplies are connected. This is required to prevent currents flowing in directions other than towards an analog or digital ground.
Rev. PrF | Page 22 of 25
Preliminary Technical Data
INTERFACING EXAMPLES
The SPI interface of the AD5371 is designed to allow the parts to be easily connected to industry standard DSPs and microcontrollers. Figure 12 shows how the AD5371 could be connected to the Analog Devices Blackfin(R) DSP. The Blackfin has an integrated SPI port which can be connected directly to the SPI pins of the AD5371 and programmable I/O pins which can be used to set or read the state of the digital input or output pins associated with the interface.
AD537x
SPISELx SCK MOSI MISO SYNC SCLK SDI SDO RESET LDAC CLR BUSY
537x-0101
AD5371
connected together. The user can write to the AD5371 by writing to the transmit register. A read operation can be accomplished by first writing to the AD5371 to tell the part that a read operation is required. A second write operation with a NOP instruction will cause the data to be read from the AD5371. The DSPs receive interrupt can be used to indicate when the read operation is complete.
ADSP-21065L
TFSx RFSx TCLKx RCLKx DTxA DRxA FLAG0 FLAG1 FLAG2 FLAG3
AD537x
SYNC SCLK SDI SDO RESET LDAC CLR BUSY
537x-0101
ADSP-BF531
PF10 PF9 PF8 PF7
Figure 13. Interfacing to an ADSP-21065L DSP
Figure 12. Interfacing to a Blackfin DSP
The Analog Devices ADSP-21065L is a floating point DSP with two serial ports (SPORTS). Figure 13 shows how one SPORT can be used to control the AD5371. In this example the Transmit Frame Synchronization (TFS) pin is connected to the Receive Frame Synchronization (RFS) pin. Similarly the transmit and receive clocks (TCLK and RCLK) are also
Rev. PrF | Page 23 of 25
Preliminary Technical Data OUTLINE DIMENSIONS
0.75 0.60 0.45 1.60 MAX
1 PIN 1
AD5371
14.00 BSC SQ
80 61 60
TOP VIEW 1.45 1.40 1.35
(PINS DOWN)
12.00 BSC SQ
0.15 0.05
SEATING PLANE
0.20 0.09 7 3.5 0 0.08 MAX COPLANARITY
20 21 40
41
VIEW A
VIEW A
ROTATED 90 CCW
0.50 BSC LEAD PITCH
0.27 0.22 0.17
COMPLIANT TO JEDEC STANDARDS MS-026-BDD
Figure 14. 80 Lead Quad Flat Package (ST-80-1) Dimensions shown in millimeters
10.00 BSC SQ A1 CORNER INDEX AREA
12 11 10 9 87 6 5 43 21 A
2.50 SQ
BALL A1 PAD CORNER TOP VIEW
8.80 BSC
BOTTOM VIEW
B C D E F G H J K L M
0.80 BSC 1.40 1.35 1.20 DETAIL A
0.65 REF 0.34 NOM 0.29 MIN
DETAILA
1.11 1.01 0.91
0.50* SEATING 0.45 PLANE 0.40 BALL DIAMETER *COMPLIANT TO JEDEC STANDARDS MO-205AC WITH THE EXCEPTION OF BALL DIAMETER.
0.12 MAX COPLANARITY
Figure 15. 100-Lead Chip Scale Package Ball Grid Array [CSP_BGA] (BC-100-2) Dimensions shown in millimeters
ORDERING GUIDE
Model AD5371BSTZ AD5371BBCZ Temperature Range -40C to +85C -40C to +85C Package Description 80-Lead Quad Flat Pack (LQFP ) 100 Ball Chip Scale Package (CSPBGA) Package Option ST-80 BC-100-2
Rev. PrF | Page 24 of 25
Preliminary Technical Data NOTES
AD5371
(c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
PR05814-0-10/06(PrF)
Rev. PrF | Page 25 of 25

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