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CS5317
16-Bit, 20 kHz Oversampling A/D Converter
Features
l Complete
Description
Voiceband DSP Front-End
The CS5317 is an ideal analog front-end for voiceband signal processing applications such as high-performance modems, passive sonar, and voice recognition systems. It includes a 16-bit A/D converter with an internal track & hold amplifier, a voltage reference, and a linear-phase digital filter. An on-chip phase-lock loop (PLL) circuit simplifies the CS5317's use in applications where the output word rate must be locked to an external sampling signal. The CS5317 uses delta-sigma modulation to achieve 16-bit output word rates up to 20 kHz. The delta-sigma technique utilizes oversampling followed by a digital filtering and decimation process. The combination of oversampling and digital filtering greatly eases antialias requirements. Thus, the CS5317 offers 84 dB dynamic range and 80 dB THD and signal bandwidths up to 10 kHz at a fraction of the cost of hybrid and discrete solutions. The CS5317's advanced CMOS construction provides low power consumption of 220 mW and the inherent reliability of monolithic devices. ORDERING INFORMATION See page 20.
-
16-Bit A/D Converter Internal Track & Hold Amplifier On-Chip Voltage Reference Linear-Phase Digital Filter
l On-Chip
PLL for Simplified Output Phase Locking in Modem Applications l 84 dB Dynamic Range l 80 dB Total Harmonic Distortion l Output Word Rates up to 20 kHz l DSP-Compatible Serial Interface l Low Power Dissipation: 220 mW
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Cirrus Logic, Inc. Crystal Semiconductor Products Division P.O. Box 17847, Austin, Texas 78760 (512) 445 7222 FAX: (512) 445 7581 http://www.crystal.com
Copyright (c) Cirrus Logic, Inc. 1997 (All Rights Reserved)
MAR `95 DS27F4 1
CS5317
ANALOG CHARACTERISTICS (TA = TMIN - TMAX; VA+, VD+ = 5V 10%; VA-, VD- = -5V 10%; CLKIN = 4.9152 MHz in CLKOR mode; 1kHz Input Sinewave; with 1.2 k, .01 F antialiasing filter.)
Parameter* Specified Temperature Range Resolution 16 (Note 1) 78 72 (Note2) (Note 3) (Note 4) (1kHz) 78.125 2.75 (Note5) Min Typ 0 to 70 84 80 84 0.4 150 500 10 50 5 80 220 300 Max Units C Bits dB dB dB LSB mV V/C mV V/C s kHz k V mW
Dynamic Performance
Dynamic Rnage Total Harmonic Distortion Signal to Intermodulation Distorition
dc Accuracy
Differential Nonlinearity Positive Full-Scale Error Positive Full-Scale Drift Bipolar Offset Error Bipolar Offset Drift
Filter Characteristics
Absolute Group Delay Passband Frequency
Input Characteristics
AC Input Impedance Analog Input Full Scale Signal Level
Power Supplies
Power Dissipation Notes: 1. Measured over the full 0 to 9.6kHz band with a -20dB input and extrapolated to full-scale. Since this includes energy in the stopband above 5kHz, additional post-filtering at the CS5317's output can typically achieve 88dB dynamic range by improving rejection above 5kHz. This can be increased to 90dB by bandlimiting the output to 2.5kHz. 2. No missing codes is guaranteed by design. 3. Group delay is constant with respect to input analog frequency; that is, the digital FIR filter has linear phase. Group delay is determined by the formula Dgrp = 384/CLKIN in CLKOR mode, or 192/CLKOUT in any mode. 4. The digital filter's frequency response scales with the master clock. Its -3dB point is determined by f-3dB = CLKIN/977.3 in CLKOR mode, or CLKOUT/488.65 in any mode. 5. All outputs unloaded. All inputs CMOS levels. * Refer to the Parameter Definitions section after the Pin Description section.
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CS5317
ANALOG CHARACTERISTICS (continued)
Parameter Power Supply Rejection VA+ VAVD+ VD(Note 6) Min Typ 60 45 60 55 0 to 70 (Note 7) -4 1.28 -3 (Note 8) -10 -8 50 -30 5.12 -12 100 Max Units dB dB dB dB C Mrad/Vs MHz A/rad ns
Specified Temperature Range
Phase-Lock Loop Characteristics
VCO Gain Constant, Ko VCO Operating Frequency Phase Detector Gain Control, Kd Phase Detector Prop. Delay
Notes: 6. With 300mV p-p, 1kHz ripple applied to each supply separately. 7. Over 1.28 MHz to 5.12 MHz VCO output range, where VCO frequency = 2 * CLKOUT. 8. Delay from an input edge to the phase detector to a response at the PHDT output pin.
DIGITAL CHARACTERISTICS (TA = TMIN - TMAX; VA+, VD+ = 5V10%; VA-, VD- = -5V10%) All measurements performed under static conditions.
Parameter High-Level Input Voltage Low-Level Input Voltage High-Level Output Voltage Low-Level Output Voltage Input Leakage Current 3-State Leakage Current Digital Output Pin Capacitance Note: IOUT = 1.6mA (Note 9) Symbol VIH VIL VOH VOL Iin IOZ Cout Min 2.0 (VD+)-1.0V Typ 9 Max 0.8 0.4 10 10 Units V V V V A A pF
9. Iout=-100A. This specification guarantees the ability to drive one TTL load (VOH=2.4V @ Iout=-40A.).
RECOMMENDED OPERATING CONDITIONS (DGND, AGND = 0V, see Note 10.)
Parameter DC Power Supplies: Positive Digital Negative Digital Positive Analog Negative Analog Symbol VD+ VDVA+ VAfclk Min 4.5 -4.5 4.5 -4.5 0.01 Typ 5.0 -5.0 5.0 -5.0 Max 5.5 -5.5 5.5 -5.5 5.12 Units V V V V MHz
Master Clock Frequency Note: 10. All voltages with respect to ground.
Specifications are subject to change without notice. DS27F4 3
CS5317
SWITCHING CHARACTERISTICS (TA = TMIN-TMAX; CL=50 pF; VD+ = 5V10%; VD- = -5V10%)
Parameter Master Clock Frequency: CLKIN CLKG1 Mode CLKG2 Mode CLKOR Mode DOUT Any Digital Input Any Digital Output Any Digital Input Any Digital Output Pulse Width Low Pulse Width High Pulse Width Low Pulse Width High Symbol fclkg1 fclkg2 fclkor fdout trisein triseout tfallin tfallout tpwl1 tpwh1 tpwl1 tpwh1 tpwr RST High to CLKIN High CLKIN High to RST High tsu1 tsu2 tphl1 tphl2 tplh1 tplh2 tplh3 tplh4 tplh5 tplh6 Min 200 200 45 45 400 40 40 Typ 20 15 20 15 1 Max 20 10 5.12 20 1000 20 1000 20 150 80 60 60 100 200 200 Units kHz kHz MHz kHz ns ns ns ns ns ns ns ns ns ns ns ns CLKOUT cycles ns ns ns ns ns
Output Word Rate: Rise Times: Fall Times:
CLKIN Duty Cycle CLKG1 and CKLG2 Modes CLKOR Mode RST Pulse Width Low Set Up Times:
Propagation Delays: DOE Falling to Data Valid CLKIN Rising to DOUT Falling (Note 11) DOE Rising to Hi-Z Output CLKOUT Rising to DOUT Falling CLKOUT Rising to DOUT Rising CLKOUT Rising to Data Valid CLKIN Rising to CLKOUT Falling (Note 12) CLKIN Rising to CLKOUT Rising (Note 12) Notes: 11. CLKIN only pertains to CLKG1 and CLKG2 modes. 12. Only valid in CLKOR mode.
ABSOLUTE MAXIMUM RATINGS (DGND, AGND = 0V, all voltages with repect to groung)
Parameter DC Power Supplies: Positive Digital Negative Digital Positive Analog Negative Analog (Note 13) Symbol VD+ VDVA+ VAIin VINA VIND TA Min -0.3 0.3 -0.3 0.3 (VA-) - 0.3 -0.3 -55 Max (VA+) + 0.3 -6.0 6.0 -6.0 10 (VA+) + 0.3 (VD+) + 0.3 125 Units V V V V mA V V C
Input Current, Any Pin Except Supplies Analog Input Voltage (AIN and VREF pins) Digital Input Voltage Ambient Operating Temperature
-65 150 C Storage Temperature Tstg Notes: 13. Transient currents up to 100mA will not cause SCR latch-up. WARNING:Operating this device at or beyond these extremes may result in permanent damage to the device. Normal operation of the part is not guaranteed at these extremes.
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CS5317
t risein t fallin 2.0 V 0.8 V
Rise and Fall Times
t pwh1 CLKIN
t riseout
t fallout 2.4 V 0.4 V
t pwl1
CLKIN Timing
CLKIN (Note 14) CLKOUT t plh2 DOUT t phl1 t plh4 15 (MSB) 14 1 0 t phl2 t plh3
t plh1
DATA
DOE (Note 15)
Serial Output Timing
CLKIN t plh5 CLKOUT t plh6 t plh5
DOUT t su2 RST (Note 16)
t su1
t su2
t su1
t pwr
Reset Timing
Notes: 14. CLKIN only pertains to CLKG1 and CLKG2 modes. 15. If DOE is brought high during serial data transfer, CLKOUT, DOUT, and DATA will immediately 3-state and the rest of the serial data is lost. 16. RST must be held high except in the clock override (CLKOR) mode where it can be used to align the phases of all internal clocks.
DS27F4
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CS5317
GENERAL DESCRIPTION The CS5317 functions as a complete data conversion subsystem for voiceband signal processing. The A/D converter, sample/hold, voltage reference, and much of the antialiasing filtering are performed on-chip. The CS5317's serial interface offers its 16-bit, 2's complement output in a format which easily interfaces with industry-standard micro's and DSP's. The CS5317 also includes a phase-locked loop that simplifies the converter's application in systems which require sampling to be locked to an external signal source. The CS5317 continuously samples its analog input at a rate set by an external clock source. On-chip digital filtering, an integral part of the delta-sigma ADC, processes the data and updates the 16-bit output register at up to 20 kHz. The CS5317 can be read at any rate up to 20 kHz. The CS5317 is a CS5316 with an on-chip sampling clock generator. As such, it replaces the CS5316 and should be considered for all new designs. In addition, a CS5316 look-alike mode is included, allowing a CS5317 to be dropped into a CS5316 socket.
modulator's 1-bit output conveys information in the form of duty cycle. The digital filter then processes the 1-bit signal and extracts a high resolution output at a much lower rate (that is, 16-bits at a 20 kHz word rate with a 5 kHz input bandwidth). An elementary example of a delta-sigma A/D converter is a conventional voltage-to-frequency converter and counter. The VFC's 1-bit output conveys information in the form of frequency (or duty-cycle), which is then filtered (averaged) by the counter for higher resolution. In comparison, the CS5317 uses a more sophisticated multi-order modulator and more powerful FIR filtering to extract higher word rates, much lower noise, and more useful system-level filtering. Filtering At the system level, the CS5317's digital filter can be modeled exactly like an analog filter with a few minor differences. First, digital filtering resides behind the A/D conversion and can thus reject noise injected during the conversion process (i.e. power supply ripple, voltage reference noise, or noise in the ADC itself). Analog filtering cannot. Also, since digital filtering resides behind the A/D converter, noise riding unfiltered on a nearfull-scale input could potentially saturate the ADC. In contrast, analog filtering removes the noise before it ever reaches the converter. To address this issue, the CS5317's analog modulator and digital filter reserve headroom such that the device can process signals with 100mV "excursions" above full-scale and still output accurately converted and filtered data. Filtered input signals above full-scale still result in an output of all ones. An Application Note called "Delta Sigma Overview" contains more details on delta-sigma conversion and digital filtering.
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THEORY OF OPERATION The CS5317 utilizes the delta-sigma technique of executing low-cost, high-resolution A/D conversions. A delta-sigma A/D converter consists of two basic blocks: an analog modulator and a digital filter. Conversion The analog modulator consists of a 1-bit A/D converter (that is, a comparator) embedded in an analog negative feedback loop with high openloop gain. The modulator samples and converts the analog input at a rate well above the bandwidth of interest (2.5 MHz for the CS5317). The
6
CS5317
SYSTEM DESIGN WITH THE CS5317 Like a tracking ADC, the CS5317 continuously samples and converts, always tracking the analog input signal and updating its output register at a 20 kHz rate. The device can be read at any rate to create any system-level sampling rate desired up to 20kHz. Clocking Oversampling is a critical function in delta-sigma A/D conversion. Although system-level output sample rates typically remain between 7kHz and 20kHz in voiceband applications, the CS5317 actually samples and converts the analog input at rates up to 2.56 MHz. This internal sampling rate is typically set by a master clock which is on the order of several megahertz. See Table1 for a complete description of the clock relationships in the various CS5317 operating modes.
Some systems such as echo-canceling modems, though, require the output sampling rate to be locked to a sampling signal which is 20 kHz or below. For this reason the CS5317 includes an on-chip phase-lock loop (PLL) which can generate its requisite 5.12 MHz master clock from a 20 kHz sampling signal. The CS5317 features two modes of operation which utilize the internal PLL. The first, termed Clock Generation 1 (CLKG1), accepts a sampling clock up to 20 kHz at the CLKIN pin and internally generates the requisite 5.12 MHz clock. The CS5317 then processes samples updating its output register at the rate defined at CLKIN, typically 20 kHz. For a 20 kHz clock input the digital filter's 3 dB corner is set at 5.239 kHz, so CLKG1 provides a factor of 2X oversampling at the system level (20 kHz is twice the minimum possible sampling frequency needed to reconstruct a 5 kHz input). The CLKG1 mode is initiated by tying the MODE input to +5V.
+5V Analog Supply 10 F 0.1 F 1 VA+
10 2 VD+ CLKIN 9 Clock Source 0.1 F 10 F
MODE
7
VD- (clock override mode / CLKOR) VD+ (clock gen. mode / CLKG1) (clock gen. mode / CLKG2)
CS5317
Analog Signal Source Signal Conditioning 11 AIN 2.75V 16 RST 3 8
uP or DSP Control
DOE VA+ 25 nF 25 k 18 17 15 0.1 F 0.1 F 10 F 12 DOUT VCOIN DATA PHDT AGND
CLKOUT
Serial 6 5
Data
Interface
-5V Analog Supply
REFBUF VA14
10
DGND VD10
4
0.1 F
10 F
Figure 1. System Connection Diagram with Example PLL Components
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CS5317
Output Word Rate Provides System-level 2X RESET Oversampling HIGH NO
Symbol CLKG2 Clock CLKG2 Gen. 2 CLKG2 CLKG1 +5V HIGH YES Clock CLKG1 Gen. 1 CLKG1 CLKOR -5V SYNC YES Clock CLKOR Override CLKOR CS5316 CS5316 FSYNC LOW YES - Delay from CLKIN rising to DOUT falling = * tdcD
Mode
Mode Pin 0V
CLKIN (kHz) 7.2 9.6 10.0 (max) 14.4 19.2 20.0 (max) 3686.4 4915.2 5120.0 (max) 5120.0 (max) 1 CLKOUT cycle
CLKOUT fsin (MHz) 1.8432 2.4576 2.56 1.8432 2.4576 2.56 1.8432 2.4576 2.56 2.56
DOUT fsout (kHz) 7.2 9.6 10.0 14.4 19.2 20.0 14.4 19.2 20.0 20.0
F (kHz) 14.4 19.2 20.0 14.4 19.2 20.0 14.4 19.2 20.0 20.0
tdcD* (ns) 542.5 406.9 390.6 542.5 406.9 390.6 N/A N/A N/A N/A
Table 1. Mode Comparisons
The second PLL mode is termed Clock Generation 2 (CLKG2) which generates its 5.12 MHz clock from a 10 kHz external sampling signal. Again, output samples are available at the system sampling rate set by CLKIN, typically 10 kHz. For the full-rated 10 kHz clock CLKG2 still sets the filter's 3 dB point at 5 kHz. Therefore, CLKG2 provides no oversampling beyond the Nyquist requirement at the system level (10 kHz : 5 kHz) and its internal digital filter provides little anti-aliasing value. The CLKG2 mode is initiated by grounding the MODE pin. The CS5317 features a third operating mode called Clock Override (CLKOR). Initiated by tying the MODE pin to -5V, CLKOR allows the 5.12 MHz master clock to be driven directly into the CLKIN pin. The CS5317 then processes samples updating its output register at fclkin/256. Since all clocking is generated internally, the CLKOR mode includes a Reset capability which allows the output samples of multiple CS5317's to be synchronized. The CS5317 also has a CS5316 compatible mode, selected by tying RST low, and using MODE (pin 7) as the FSYNC pin. See the CS5316 data sheet for detailed timing information.
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Analog Design Considerations DC Characteristics The CS5317 was designed for signal processing. Its analog modulator uses CMOS amplifiers resulting in offset and gain errors which drift over temperature. If the CS5317 is being considered for low-frequency (< 10 Hz) measurement applications, Crystal Semiconductor recommends the CS5501, a low-cost, d.c. accurate, delta-sigma ADC featuring excellent 60 Hz rejection and a system-level calibration capability. The Analog Input Range and Coding Format The input range of the CS5317 is nominally 3V, with 250 mV possible gain error. Because of this gain error, analog input levels should be kept below 2.75V. The converter's serial output appears MSB-first in 2's complement format. Antialiasing Considerations In applying the CS5317, aliasing occurs during both the initial sampling of the analog input at fsin (~2.5 MHz) and during the digital decimation process to the 16-bit output sample rate, fsout.
DS27F4
CS5317
Initial Sampling The CS5317 samples the analog input, AIN, at one-half the master clock frequency (~2.5 MHz max). The input sampling frequency, fsin, appears at CLKOUT regardless of whether the master clock is generated on-chip (CLKG1 and CLKG2 modes) or driven directly into the CS5317 (CLKOR mode). The digital filter then processes the input signal at the input sample rate. Like any sampled-data filter, though, the digital filter's passband spectrum repeats around integer multiples of the sample rate, fsin. That is, when the CS5317 is operating at its full-rated speed any
Mag H(ej ) (dB)
-2.74 dB 0
noise within 5 kHz bands around 2.5 MHz, 5 MHz, 7.5 MHz, etc. will pass unfiltered and alias into the baseband. Such noise can only be filtered by analog filtering before the signal is sampled. Since the signal is heavily oversampled (2.5 MHz : 5 kHz, or 500 : 1), a single-pole passive RC filter can be used as shown in Figure 2.
Input Signal 1.2 K 0.01F AIN
Note: Any nonlinearities contributed by this filter will be encoded as distortion by the CS5317. Therefore a low distortion, high frequency capacitor such as COG-ceramic is recommended.
Figure 2. Anti-alias Filter
-40
-80 0 .25 F .5 F 5 kHz 10 kHz dc F 20 kHz 2F 40 kHz 3F 60 kHz
f
sin(128T) 128sin(T) =
3
Magnitude where: T = 1/ sin sin = = = = F= = sout = sout = input sampling frequency = CLKOUT frequency for all modes CLKIN/2 in CLKOR mode CLKIN*128 in CLKG1 mode CLKIN*256 in CLKG2 mode sin/128 for all modes input frequency sin/128 = output data rate for CLKOR & CLKG1 = F sin/256 = output data rate for CLKG2 = F/2
Examples:
For sin = 2.56 MHz at = 5 kHz: Magnitude is -2.74 dB For sin = 2.56 MHz at = 10 kHz: Magnitude is -11.8 dB Figure 3. CS5317 Low-Pass Filter Response
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CS5317
Decimation Aliasing effects due to decimation are identical in the CLKOR and CLKG1 modes. Aliasing is different in the CLKG2 mode due to the difference in output sample rates (10 kHz vs. 20 kHz) and thus will be discussed separately. Aliasing in the CLKOR and CLKG1 Modes The delta-sigma modulator output is fed into the digital low-pass filter at the input sampling rate, fsin. The filter's frequency response is shown in Figure 3. In the process of filtering the digitized signal the filter decimates the sampling rate by 128 (that is, fsout = fsin/128). In its most elementary form, decimation simply involves ignoring or selectively reading - a fraction of the available samples. In the process of decimation the output of the digital filter is effectively resampled at fsout, the output word rate, which has aliasing implications. Residual signals after filtering at multiples of fsout will alias into the baseband. For example, an input tone at 28 kHz will be attenuated by 39.9 dB. If fsout = 20 kHz, the residual tone will alias into the baseband and appear at 8 kHz in the output spectrum. If the input signal contains a large amount of outof-band energy, additional analog and/or digital antialias filtering may be required. If digital postfiltering is used to augment the CS5317's rejection above fsout/4 (that is, above 5 kHz), the filtering will also reject residual quantization
noise from the modulator. This will typically increase the converter's dynamic range to 88 dB. Further bandlimiting the digital output to fsout/8 (2.5 kHz at full speed) will typically increase dynamic range to 90 dB. Aliasing in the CLKG2 Mode Aliasing effects in the CLKG2 mode can be modeled exactly as those in the CLKG1 mode with the output decimated by two (from 20 kHz to 10 kHz). This is most easily achieved by ignoring every other sample. In the CLKG2 mode the ratio of the output sampling rate to the filter's -3 dB point is two, with no oversampling beyond the demands of the Nyquist criterion. Without the ability to roll-off substantially before fsout/2, the on-chip digital filter's antialiasing value is diminished. The CLKG2 mode should therefore be used only when the output data rate must be minimized due to communication and/or storage reasons. In addition, adequate analog filtering must be provided prior to the A/D converter. Digital Design Considerations The CS5317 presents its 16-bit serial output MSB-first in 2's complement format. The converter's serial interface was designed to easily interface to a wide variety of micro's and DSP's. Appendix A offers several hardware interfaces to industry-standard processors.
f out DOUT CLKOUT DATA
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 14
MSB (sign bit)
Figure 4. Data Output 10
LSB
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CS5317
Data Output Characteristics & Coding Format As shown in Figure 4, the CS5317 outputs its 16bit data word in a serial burst. The data appears at the DATA pin on the rising edge of the same CLKOUT cycle in which DOUT falls. Data changes on the rising edge of CLKOUT, and can be latched on the falling edge. The CLKOUT rate is set by the CLKIN input (fclkin/2 in the CLKOR mode; fclkin*128 in the CLKG1 mode; and fclkin*256 in the CLKG2 mode). DOUT returns high after the last bit is transmitted. After transmitting the sixteen data bits, DATA will remain high until DOUT falls again, initiating the next data output cycle. A 3-state capability is available for bus-oriented applications. The 3-state control input is termed Data Output Enable, DOE, and is asynchronous with respect to the rest of the CS5317. If DOE is taken high at any time, even during a data burst, the DATA, DOUT and CLKOUT pins go to a high impedance state. Any data which would be output while DOE is high is lost. Power Supplies Since the A/D converter's output is digitally filtered in the CS5317, the device is more forgiving and requires less attention than conventional 16bit A/D converters to grounding and layout arrangements. Still, care must be taken at the design and layout stages to apply the device properly. The CS5317 provides separate analog and digital power supply connections to isolate digital noise from its analog circuitry. Each supply pin should be decoupled to its respective ground, AGND or DGND. Decoupling should be accomplished with 0.1 F ceramic capacitors. If significant low frequency noise is present in the supplies, 10 F tantalum capacitors are recommended in parallel with the 0.1 F capacitors. The positive digital power supply of the CS5317 must never exceed the positive analog supply by more than a diode drop or the chip could be perDS27F4
manently damaged. If the two supplies are derived from separate sources, care must be taken that the analog supply comes up first at power-up. Figure 1 shows a decoupling scheme which allows the CS5317 to be powered from a single set of 5V rails. The digital supplies are derived from the analog supplies through 10 resistors to prevent the analog supply from dropping below the digital supply. PLL Characteristics A phase-locked loop is included on the CS5317 and is used to generate the requisite high frequency A/D sampling clock. A functional diagram of the PLL is shown in Figure 5. The PLL consists of a phase detector, a filter, a VCO (voltage-controlled oscillator), and a counter/divider. The phase detector inputs are CLKIN (1) and a sub-multiple of the VCO output signal (2). The inputs to the phase detector are positive-edge triggered and therefore the duty cycle of the CLKIN signal is not significant. With this type of phase detector, the lock range of the PLL is equal to the capture range and is independent of the low pass filter. The output of the phase detector is input to an external low pass filter. The filter characteristics are used to determine the transient response of the loop. The output voltage from the filter functions as the input control voltage to the VCO. The output of the VCO is then divided in frequency to provide an input to the phase detector. The clock divider ratio is a function of the PLL mode which has been selected. Phase Detector Gain (Kd) A properly designed and operating phase-locked loop can be described using steady state linear analysis. Once in frequency lock, any phase difference between the two inputs to the phase detector cause a current output from the detector during the phase error. While either the +50 A or the -50 A current source may be turned on, the average current flow is:
11
CS5317
ioutavg = Kd(1-2) (-50A 2) (1-2) where 1 is the phase of IN1, 2 is the phase of IN2 and Kd is the phase detector gain. The factor 2 comes from averaging the current over a full CLKIN cycle. Kd is in units of micro-amperes/radian. VCO Gain (Ko) The output frequency from the VCO ranges from 1.28 MHz to 5.12 MHz. The frequency is a function of the control voltage input to the VCO. The VCO has a negative gain factor, meaning that as the control voltage increases more positively the output frequency decreases. The gain factor units are Megaradians per Volt per Second. This is equivalent to 2 Megahertz per volt. Changes in output frequency are given by: vco = Ko VCOin [Ko is typ. -10Mrad/Vs.] Counter/Divider Ratio The CS5317 PLL multiplies the CLKIN rate by an integer value. To set the multiplication rate, a counter/divider chain is used to divide the VCO output frequency to develop a clock whose frequency is compared to the CLKIN frequency in the phase detector. The binary counter/divider ra+5V Kd = -8 A/rad 1 CLKIN IN1 DOWN 50 A C2 VA+
tio sets the ratio of the VCO frequency to the CLKIN frequency. As illustrated in Figure 5, the VCO output is always divided by two to yield the CLKOUT signal which is identical in frequency to the delta-sigma modulator sampling clock. The CLKOUT signal is then further divided by either 128 in the CLKG1 mode or by 256 in the CLKG2 mode. When the divide by two stage is included, the divider ratio (N) for the PLL in the CLKG1 mode is effectively 256. In the CLKG2 mode the divider ratio (N) is 512. Loop Transfer Function As the phase-locked loop is a closed loop system, an equation can be determined which describes its closed loop response. Using the gain factors for the phase detector and the VCO, the filter arrangement and the counter/divider constant N, analysis will yield the following equation which describes the transfer function of the PLL: KoKdR KoKd s+ 2 NC N = 1 s2 + KoKdR s + KoKd N NC This equation may be rewritten such that its elements correspond with the following
External RC C R VCO CLKOR 2 CLKOR K0 = -10 Mrad/V.s Delta-Sigma Sampling Clock (CLKOUT)
Phase/Frequency Detect Logic IN2 2
50 A
PHDT
VCOIN
UP
-5V CLKG2 2 CLKG1 Conversion Output Rate Same Frequency as DOUT Internal Sync for Digital Filter 128
Figure 5. PLL Functional Diagram 12 DS27F4
CS5317
characteristic form in which the damping factor, , and the natural frequency, n , are evident: 2 2ns + n 2 =2 1 s + 2ns + n 2 Both the natur al frequency and the damping factor are particularly important in determining the transient response of the phase-locked loop when subjected to a step input of phase or frequency. A family of curves are illustrated in Figure 6 that indicate the overshoot and stability of the loop as a function of the damping factor. Each response is plotted as a function of the normalized time, n t. For a given and lock time, t, the n required can be determined. Alternatively, phase lock control loop bandwidth may be a specified parameter. In some systems it may be desirable to reduce the -3dB bandwidth of the PLL control loop to reduce the effects of jitter in the phase of the input clock. The 3 dB bandwidth of the PLL control loop is defined by the following equation:
CLKIN is approximately 20 times greater than the 3 dB corner frequency of the control loop. Filter Components Using the equations which describe the transfer function of the PLL system, the following external filter component equations can be determined: C= KoKd
Nn 2
N KoKd
R = 2n
The gain factors (Ko, Kd) are specified in the Analog Characteristics table. In the event the system calls for very low bandwidth, hence a corresponding reduction in loop gain, the phase detector gain factor Kd can be reduced. A large series resistor (R1) can be inserted between the output of the detector and the filter. Then the 50 A current sources will saturate to the supplies and yield the following gain factor: Kd -5V 2R1
3dB = n1 22 + 1 + (22 + 1)2 +
The equations used to describe the PLL and the 3 dB bandwidth are valid only if the frequency of
20 log(2/1) 2 normalized to 1
1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 1 2 3 4 5 6 7 8 9 10
= 0.5
4
= 0.5 = 0.6 = 0.7 = 0.8 = 0.9 = 1.0 = 1.5 = 2.0 = 3.0 = 10.0
3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 0.1 1
= 0.5 = 10
= 10.0
t. n
10
Figure 6a. 2 Unit Step Response DS27F4
/n
Figure 6b. Second Order PLL Frequency Response 13
CS5317
In some applications additional filtering may be useful to eliminate any jitter associated with the discrete current pulses from the phase detector. In this case a capacitor whose value is no more than 0.1 C can be placed across the RC filter network (C2 in Figure 5). Filter Design Example The following is a step by step example of how to derive the loop filter components. The CS5317 A/D sampling clock is to be derived from a 9600 Hz clock source. The application requires the signal passband of the CS5317 to be 4 kHz. The on-chip digital filter of the CS5317 has a 3 dB passband of CLKOUT/488.65 (see Note 4 in the data sheet specifications tables). The 4 kHz passband requirement dictates that the sample clock (CLKOUT) of the CS5317 be a minimum of 4000 X 488.65 = 1.954 MHz. This requires the VCO to run at 3.908 MHz. The 3.908 MHz rate is 407 times greater than the 9600 Hz PLL input clock. Therefore the CS5317 must be set up in mode CLKG2 with N = 512. If the CLKG1 mode were used (N = 256), too narrow of a signal bandwidth through the A/D would result. Once the operating mode has been determined from the system requirements, a value for the damping factor must be chosen. Figure 6 illustrates the dynamic aspects of the system with a given damping factor. Damping factor is generally chosen to be between 0.5 and 2.0. The choice of 0.5 will result in an overshoot of 30 % to a step response whereas the choice of 2.0 will result in an overshoot of less than 5 %. For example purposes, let us use a damping factor of 1.0. So, let us begin with the following variables : Ko = - 10 Mradians/volt.sec Kd = - 8 A/radian N = 512 = 1.0
To calculate values for the resistor R and capacitor C of the filter, we must first derive a value for n. Using the general rule that the sample clock should be at least 20 times higher frequency than the 3dB bandwidth of the PLL control loop: CLKIN 20 3dB where CLKIN = 9600 Hz = 2 9600 radians/sec. So: 3dB = 2 9600/20 = 3016 radians/sec. Knowing 3dB and the damping factor of 1.0, we can calculate the natural frequency, n , of the control loop: n = 3dB1 22 + 1 + (22 + 1)2 + n = 3016 1 2(1)2 + 1 + (2(1)2 + 1)2 + n = 1215 1 sec
Once the natural frequency, n , is determined, values for R and C for the loop filter can be calculated: R = 2nN/KoKd R = 2(1)(1215 1/s) 512/(-10Mrad/v.s.)(-8 A/rad) R = 15552 v/A = 15.55 k. Use R = 15 k. C = KoKd/Nn2 C = (-10 Mrad/v.s)(- 8 A/rad)/512 (1215 1/s)2 C = 105.8 x 10 -9 A.s/v = 105 nF. Use 0.1 F.
The above example assumed typical values for Ko and Kd. Your application may require a worst case analysis which includes the minimum or maximum values. Table 2 shows some other example situations and R and C values.
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14
CS5317
CLKIN CLKOUT 3dB n R * (k) C * (nF) (Hz) Mode N (MHz) 7200 CLKG2 512 1.8432 1.0 2262 911 11.6 187 9600 CLKG2 512 2.4576 1.0 3016 1215 15.5 106 14400 CLKG1 256 1.8432 1.0 4524 1822 11.6 94 19200 CLKG1 256 2.4576 1.0 6032 2430 15.5 52 * The values for R and C are as calculated using the described method. Component tolerances have not been allowed for. Notice that Ko and Kd can vary over a wide range, so using tight tolerances for R and C is not justified. Use the nearest conveniently available value. Table 2 Example PLL Loop Filter R and C values
CS5317 PERFORMANCE The CS5317 features 100% tested dynamic performance. The following section is included to illustrate the test method used for the CS5317. FFT Tests and Windowing The CS5317 is tested using Fast Fourier Transform (FFT) techniques to analyze the converter's dynamic performance. A pure sine wave is applied to the CS5317 and a "time record" of 1024 samples is captured and processed. The FFT algorithm analyzes the spectral content of the digital waveform and distributes its energy among 512 "frequency bins". Assuming an ideal sinewave, distribution of energy in bins outside of the fundamental and dc can only be due to quantization effects and errors in the CS5317. If sampling is not synchronized to the input sinewave it is highly unlikely that the time record will contain an exact integer number of periods of the input signal. However, the FFT assumes that the signal is periodic, and will calculate the spectrum of a signal that appears to have large discontinuities, thereby yielding a severely distorted spectrum. To avoid this problem, the time record is multiplied by a window function prior to performing the FFT. The window function smoothly forces the endpoints of the time record to zero, removing the discontinuities. The effect of the "window" in the frequency domain is to convolute the spectrum of the window with that of the actual input.
DS27F4
The quality of the window used for harmonic analysis is typically judged by its highest sidelobe level. The Blackman-Harris window used to test the CS5317 has a maximum side-lobe level of -92 dB. Figure 7 shows an FFT plot of a typical CS5317 with a 1 kHz sinewave input generated by an "ultra-pure" sine wave generator and the output multiplied by a Blackman-Harris window. Artifacts of windowing are discarded from the signal-to-noise calculation using the assumption that quantization noise is white. All FFT plots in this data sheet were derived by averaging the FFT results from ten time records. This filters the spectral variability that can arise from capturing finite time records, without disturbing the total energy outside the fundamental. All harmonics and the -92 dB side-lobes from the BlackmanHarris window are therefore clearly visible in the plots.
0dB -20dB -40dB -60dB Signal Amplitude Relative to Full Scale -80dB -100dB -120dB 1 kHz Input Frequency 9.6 kHz Sampling Rate: 19.2 kHz Full Scale: _ + 2.75 V S/(N+D): 81.39 dB
dc
Figure 7. CS5317 Dynamic Performance 15
CS5317
Full - scale signal - to - noise - plus - distortion [S/(N+D)] is calculated as the ratio of the rms power of the fundamental to the sum of the rms power of the FFT's other frequency bins, which include both noise and distortion. For the CS5317, signal-to-noise-plus-distortion is shown to be better than 81 dB for an input frequency range of 0 to 9.6 kHz (fs/2). Harmonic distortion characteristics of the CS5317 are excellent at 80 dB full scale signal to THD (typical), as are intermodulation distortion characteristics, shown in Figure 8. Intermodulation distortion results from the modulation distortion of two or more input frequencies by a non-linear transfer function. DNL Test Figure 9 shows a plot of the typical differential non-linearity (DNL) of the CS5317. This test is done by taking a large number of conversion results, and counting the occurrences of each code. A perfect A/D converter would have all codes of equal size and therefore equal numbers of occurrences. In the DNL test, a code with the average number of occurrences is considered ideal and plotted as DNL = 0 LSB. A code with more or less occurrences than average will appear as a DNL of greater than or less than zero. A missing code has zero occurrences, and will appear as a DNL of -1 LSB.
0dB S/I.M.D.: 84.7 dB -20dB -40dB -60dB Signal Amplitude Relative to Full Scale -80dB -100dB -120dB 800 1450 Input Frequency (Hz) 9600
dc
Figure 8. CS5317 Intermodulation Distortion
The plot below illustrates the typical DNL performance of the CS5317, and clearly shows the part easily achieves no missing codes.
Schematic & Layout Review Service
Confirm Optimum Schematic & Layout Before Building Your Board. For Our Free Review Service Call Applications Engineering.
Call: (512) 445-7222
+1
+1/2
DNL (LSB)
0
-1/2
-1
0
32,768
65,535
Codes Figure 9. CS5317 DNL Plot 16 DS27F4
CS5317
PIN DESCRIPTIONS
(Pin numbers refer to the 18-pin DIP package)
18 pin DIP Pinout
POSITIVE ANALOG POWER VA+ POSITIVE DIGITAL POWER VD+ DOE DATA OUTPUT ENABLE DIGITAL GROUND DGND SERIAL CLOCK OUTPUT CLKOUT SERIAL DATA OUTPUT DATA CLOCKING MODE SELECT MODE DOUT DATA OUTPUT READY CLOCK INPUT CLKIN
1 2 3 4 5 6 7 8 9 18 17 16 15 14 13 12 11 10
VCOIN PHDT RST AGND VANC REFBUF AIN VD-
VCO INPUT PHASE DETECT RESET ANALOG GROUND NEGATIVE ANALOG POWER NO CONNECT POSITIVE REFERENCE BUFFER ANALOG INPUT NEGATIVE DIGITAL POWER
20 pin SOIC pinout
POSITIVE ANALOG POWER VA+ POSITIVE DIGITAL POWER VD+ DOE DATA OUTPUT ENABLE DIGITAL GROUND DGND NO CONNECT NC SERIAL CLOCK OUTPUT CLKOUT SERIAL DATA OUTPUT DATA CLOCKING MODE SELECT MODE DOUT DATA OUTPUT READY CLOCK INPUT CLKIN
1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11
VCOIN PHDT RST AGND NC NC VAREFBUF AIN VD-
VCO INPUT PHASE DETECT RESET ANALOG GROUND NO CONNECT NO CONNECT NEGATIVE ANALOG POWER POSITIVE REFERENCE BUFFER ANALOG INPUT NEGATIVE DIGITAL POWER
Power Supplies VD+ - Positive Digital Power, PIN 2. Positive digital supply voltage. Nominally 5 volts. VD- - Negative Digital Power, PIN 10. Negative digital supply voltage. Nominally -5 volts. DGND - Digital Ground, PIN 4. Digital ground reference. VA+ - Positive Analog Power, PIN 1. Positive analog supply voltage. Nominally 5 volts. VA- - Negative Analog Power, PIN 14. Negative analog supply voltage. Nominally -5 volts. AGND - Analog Ground, PIN 15. Analog ground reference. PLL/Clock Generator CLKIN - Clock Input, PIN 9. Clock input for both clock generation modes and the clock override mode (see MODE).
DS27F4 17
CS5317
MODE - Mode Set, PIN 7. Determines the internal clocking mode utilized by the CS5317. Connect to +5V to select CLKG1 mode. Connect to DGND to select CLKG2 mode. Connect to -5V to select CLKOR mode. This pin becomes equivalent to FSYNC in the CSZ5316 compatible mode. VCOIN - VCO Input, PIN 18. This pin is typically connected to PHDT. A capacitor and resistor in series connected between VA+ and this pin sets the filter response of the on-chip phase locked loop. PHDT - Phase Detect, PIN 17. This pin is typically connected to VCOIN. A capacitor and resistor in series connected between VA+ and this pin sets the filter response of the on-chip phase locked loop. Inputs AIN - Analog Input, PIN 11. DOE - Data Output Enable, PIN 3. Three-state control for serial output interface. When low, DATA, DOUT, and CLKOUT are active. When high, they are in a high impedance state. RST - Sample Clock Reset, PIN 16. Sets phase of CLKOUT. Functions only in the clock override mode, CLKOR. Used to synchronize the output samples of multiple CS5317's. Must be kept high in CLKG1 or CLKG2 modes. Also, tying this pin low, with MODE not tied to - 5V, will place the CS5317 into CSZ5316 compatible mode. Outputs DOUT - Data Output Flag, PIN 8. The falling edge indicates the start of serial data output on the DATA pin. The rising edge indicates the end of serial data output. DATA - Data Output, PIN 6. Serial data output pin. Converted data is clocked out on this pin by the rising edge of CLKOUT. Data is sent MSB first in two's complement format. CLKOUT - Data Output Clock, PIN 5. Serial data output clock. Data is clocked out on the rising edge of this pin. The falling edge should be used to latch data. Since CLKOUT is a free running clock, DOUT can be used to indicate valid data. REFBUF - Positive Voltage Reference Noise Buffer, PIN 12. Used to attenuate noise on the internal positive voltage reference. Must be connected to the analog ground through a 0.1F ceramic capacitor.
18
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CS5317
PARAMETER DEFINITIONS Resolution - The number of different output codes possible. Expressed as N, where 2N is the number of available output codes. Dynamic Range - The ratio of the largest allowable input signal to the noise floor. Total Harmonic Distortion - The ratio of the rms sum of all harmonics to the rms value of the largest allowable input signal. Units in dB's. Signal to Intermodulation Distortion - The ratio of the rms sum of two input signals to the rms sum of all discernible intermodulation and harmonic distortion products. Linearity Error - The deviation of a code from a straight line passing through the endpoints of the transfer function after zero- and full-scale errors have been accounted for. "Zero-scale" is a point 1/2 LSB below the first code transition and "full-scale" is a point 1/2 LSB beyond the code transition to all ones. The deviation is measured from the middle of each particular code. Units in %FS. Differential Nonlinearity - The deviation of a code's width from the ideal width. Units in LSB's. Positive Full Scale Error - The deviation of the last code transition from the ideal, (VREF - 3/2 LSB). Units in mV. Positive Full Scale Drift - The drift in effective, positive, full-scale input voltage with temperature. Negative Full Scale Error - The deviation of the first code transition from the ideal, (-VREF + 1/2 LSB). Units in mV. Negative Full Scale Drift - The drift in effective, negative, full-scale input voltage with temperature. Bipolar Offset - The deviation of the mid-scale transition from the ideal. The ideal is defined as the middle transition lying on a straight line between actual positive full-scale and actual negative full-scale. Bipolar Offset Drift - The drift in the bipolar offset error with temperature. Absolute Group Delay - The delay through the filter section of the part. Passband Frequency - The upper -3 dB frequency of the CS5317.
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19
CS5317
ORDERING GUIDE
Model Number CS5317-KP CS5317-KS Temperature Range 0 to 70C 0 to 70C Package 18 Pin Plastic DIP 20 Pin Plastic SOIC
20
DS27F4
CS5317
APPENDIX A APPLICATIONS
Figure A1 shows one method of converting the serial output of the CS5317 into 16-bit, parallel words. The associated timing is also shown.
+5V
CS5317 DATA CLKOUT DOUT
A
OE2 P A P B 74HCT299 P C P D P E P F P G P H OE1
D0 D1 D2 D3 D4 D5 D6 D7 16 Data Bus 8
S1
S2
QH +5V
CS OE2 OE1 P A A 74HCT299 P B P C P D P E P F P G P H
D8 D9 D10 D11 D12 D13 D14 D15 8
S1 S2
74HCT74
D
SET
Q
INT
Q
INT
Only needed for level sensitive interrupt driven systems.
CLKOUT
DOUT
DATA
15 (MSB)
14
13
2
1
0
INT INT Cleared when data read (CS goes low)
Figure A1. CS5317-to-Parallel Data Bus Interface DS27F4 21
CS5317
Figure A2 shows the interconnection and timing details for connecting a CS5317 to a NEC PD7730 DSP chip.
Figure A3 shows the interconnection and timing details for connecting a CS5317 to a Motorola DSP 56000.
PD77230 SICK SIEN SI
CS5317 Status Register (SR) Bit Mnemonic Setting Meaning 9 SCI 0 External Clock 7, 6 SDLI 1, 0 16 bit data 3 SIF 0 MSB First CLKOUT DOUT DATA
CLKOUT
DOUT DATA 15 (MSB) 14 13 2 1 0
Figure A2. CS5317-to-NEC PD77230 Serial Interface
SSI Control Reg. B CRB (X:FFED)
SSI Control Reg. A CRA (X:FFEC) WL1 = 1 16 bits WL0 = 0
SYNC ASYNC CLKOUT SCK SC0 PINS DOUT SC2 SC1 GCK 0 0 SYN 1 0 FSL 0 0 SCKD 0 SCD2 0 SCD1 0 SCD0 0
CS5317 CLKOUT DOUT DATA
DSP56000 SCK, SC0 SC2, SC1 SRD
CLKOUT
DOUT
DATA
15 (MSB)
14
13
2
1
0
Figure A3. CS5317-to-Motorola DSP56000 Serial Interface 22 DS27F4
CS5317
Figure A4 shows the interconnection and timing details for connecting a CS5317 to a WE DSP16 DSP chip.
Serial I/O Control Register (SIOC) Field Value Meaning MSB 1 MSB input first ILD 0 ILD is an input ICK 0 ICK is an input ILEN 0 16 bit input data
Figure A5 shows the interconnection and timing details for connecting a CS5317 with TMS32020 and TMS320C25 DSP chips.
DSP16 ICK ILD D 74 Q DATA d DI
CS5317 CLKOUT DOUT DATA
CLKOUT
DOUT
DATA d
15 (MSB)
14
13
2
1
0
Figure A4. CS5317-to-WE DSP16 Serial Interface
CS5317 TMS32020 Status Register (ST1): F0 = 0 (16 bit data) TMS320C25 Status Register (ST1): F0 = 0 (16 bit data) FSM = 1 (Frame Sync used) CLKOUT DOUT DATA
TMS32020 TMS320C25 CLKR FSR DR
CLKOUT
DOUT
DATA
15 (MSB)
14
13
2
1
0
Figure A5. CS5317-to-TMS32020/TMS320C25 Serial Interface
DS27F4
23
* Notes *
CDB5317
Evaluation Board for CS5317
Features Description
The CDB5317 Evaluation Board is designed to allow the user to quickly evaluate performance of the CS5317 Delta-Sigma Analog-to-Digital Converter. All that is required to use this board is an external power supply, a signal source, a clock source, and an ability to read either serial or parallel 16bitdata words. ORDERING INFORMATION CDB5317 Evaluation Board
l Easy to Use Digital Interface
Parallel 16 Bits With Clock Serial Output With Clock l Multiple Operating Modes Including Two PLL Modes l IDC Header used to access Parallel Data, Serial Data, and Clock Input and Output
I
AIN
+5V GND -5V
V L
CLKIN
CLKIN CS5317
CLKOUT DATA
SERIAL TO PARALLEL CONVERTER
IDC HEADER
DRDY DACK D0-D15
Cirrus Logic, Inc. Crystal Semiconductor Products Division P.O. Box 17847, Austin, Texas 78760 (512) 445 7222 FAX: (512) 445 7581 http://www.crystal.com
Copyright (c) Cirrus Logic, Inc. 1998 (All Rights Reserved)
MAR `95 DS27DB3 25
CDB5317 GENERAL DESCRIPTION The CDB5317 Evaluation Board is a stand-alone environment for easy lab evaluation of the CS5317 Delta-Sigma Analog-to-Digital Converter. Included on the board is a serial-to-parallel converter. The user can access output data in either parallel or serial form. When supplied with the necessary +5 V and -5 V power supplies, a CLKIN signal, and an analog signal source, the CDB5317 will provide converted data at the 40 pin header. SUGGESTED EVALUATION METHOD An efficient evaluation of the CS5317 using the CDB5317 may be accomplished as described below. The following equipment will be required for the evaluation: * The CDB5317 Evaluation Board. * A power supply capable of supplying +5V and -5V. * A clock source as the CLKIN signal of the CS5317. * A spectrally pure sine wave generator such as the Krohn-Hite Model 4400A "Ultra-Low Distortion Oscillator". * A PC equipped with a digital data acquisition board such as the Metrabyte Model PIO12 "24 Bit Parallel Digital I/O Interface". * A software routine to collect the data and perform a Fast Fourier Transform (FFT). The evaluation board includes filter components for the on-chip phase locked loop. The components are adequate for testing if the CLKIN signal has little or no phase-jitter. If the CDB5317 board is being tested as part of a system which generates a CLKIN which contains jitter, the PLL filter components may need to be optimized for your system (see the CS5317 data sheet). Set-up for evaluation is straightforward. First decide the operating mode and place the jumper on the board for the proper selection. Then decide whether the filter components for the phase locked loop are adequate or whether they should be changed for your evaluation. The PLL will lock on a steady clock input with the filter as it is. Connect the necessary 5 V (CMOS compatible) CLKIN signal for the application. Use the sinewave generator to supply the analog signal to the CDB5317. Apply the analog input and CLKIN signals only when the evaluation board is powered up. Converted data will then appear at the header on the CDB5317. The header should be connected to the digital data acquisition board in the PC through an IDC 40 pin connector and cable. The software routine should collect the data from the CDB5317 and run a standard 1024 point Fast Fourier Transform (FFT). Such an analysis results in a plot similar to Figure 1. This plot resulted from using a 1kHz input signal and a Blackman-Harris window for the FFT. The signal to noise and signal to total harmonic distortion characteristics of the CS5317 may be easily measured in this way. The signal to total harmonic distortion value for a particular input is the ratio of the RMS value of the input signal and the sum of the RMS values of the harmonics shown in the diagram. The dynamic range of the CS5317 can be measured by reducing the input
0dB -20dB -40dB Signal -60dB Amplitude Relative to Full Scale -80dB -100dB Sampling Rate: 19.2 kHz Full Scale: 2.75 V S/(N+D): 81.39 dB
-120dB dc
1 kHz Input Frequency 9.6 kHz
Figure 1. FFT Plot Example 26 DS27DB3
CDB5317 amplitude so that distortion products become negligible. This allows an accurate measurement of the noise floor. More complex analysis such as intermodulation distortion measurements can be accomplished with the addition of another sine-wave generator. are supplied on the board to connect the +5, -5, and ground power lines. A good quality low ripple, low noise supply will give the best performance. The +5 V supply can also be used for VL and should be connected between the VL board jack and the power supply, as opposed to connecting the VL jack straight to the +5V jack. The +5V jack is the positive power source for the CS5317 IC whereas the VL jack supplies power to all the digital ICs. Care should be taken that noise is not coupled between VL and +5V; however, supply noise is generally not a problem with the CS5317 since the on-chip decimation filter will remove any interference outside of its passband. The +5 and -5 V supply lines are filtered on
CIRCUIT DESCRIPTION Figure 2 illustrates the CS5317 A/D converter IC circuit connections. The chip operates off of 5V. These voltages are supplied from a power source external to the evaluation board. Binding posts
TP6 VL D1 TP10 +5V 6.8v D3 C19 C17 0.22F R10 10k R2 200 R1* 51 AIN R11 1.2k C18 0.01 F NPO TP8 C9 10F C8 0.1 F 1 VA+ C5 C4 VL
0.1 F 10 F R7 10 2 VD+ 3 + C6 10 F R5 10 k DOUT (fig. 3) CLKOUT (fig. 3) DATA (fig. 3) R6 10 k C7 0.1 F
17 PHDT 18 VCOIN 9 CLKIN
DOE
CLKIN
CLKIN (fig.6) 11 U6 AIN
8 DOUT 5 CLKOUT 6 DATA 16 RST
R9 10 k
12 REFBUF C14 0.1 F 15 AGND VA14 R8 10 C15
MODE
7
CLKG1 CLKG2 P2 CLKOR
TP7 GND D2 TP9 -5V C16
CS5317 DGND VD10 4 C13 C12 + 10 F
6.8v
10F 0.1 F
0.1 F
* Remove for logic gate CLKIN source
Figure 2. Analog-to-Digital Converter
DS27DB3
27
CDB5317 the board and then connected to the VA+ and VAsupply pins of the chip. The +5 V and -5V are then connected by means of ten resistors to the VD+ and VD- pins respectively. Capacitive filtering is provided on all supply pins of the chip. In addition there is a 0.1 F filter capacitor connected from the REFBUF pin of the chip to the VA- supply pin. To properly operate, the CS5317 chip requires an external (5 V CMOS compatible) clock. A BNC connector labeled CLKIN is provided to connect the off-board clock signal to the board. The CLKIN signal is also available on the 40 pin header connector. The CLKIN signal is one input to the phase detector of the on-chip phase locked loop of the CS5317. Header connector P2 (see Figure 2) is provided to allow mode selection for the CS5317 chip. The mode selection works together with the CLKIN signal to set the sample rate and the output word rate of the CS5317. See the CS5317 data sheet for details on mode selection. Two of the available modes (CLKG1 and CLKG2) utilize the on-chip phase locked loop to step up the CLKIN frequency to obtain the necessary sample rate clock for the A/D converter. Another mode (the CLKOR mode) does not use the on-chip PLL but instead drives the sample function directly. The
VL
DOUT2 (fig. 6) C10 0.1 F S D 5 DRDY (fig. 6) VL TP2
U5
1 3 9 11 13 2 4 8 10 12 DOUT (fig. 2) 1
VL
C1 0.1 F 14 7 2 13 14 2 D 4
12
U4 Q 74HC74 3 CL Q GND R 7
6
UNUSED GATES VL 10 VL VL 12 9 DSQ U4 11 CL 8 RQ VL 13
CLKOUT (fig. 2)
3 U1
4 5 6
VL TP3 0.1 F C11 14 DACK 5 6 U5 (fig. 6) R4 7 10k CLKOUT (fig. 6) CLKOUT2 (fig. 6)
DATA (fig. 2)
11
10
9
8
DATA 1 (fig. 6) DATA (fig. 6)
Figure 3. Buffers and Parallel Handshake Flip-Flop
28
DS27DB3
CDB5317
CLKOUT DATA DOUT Note: For a complete description of serial timing see the CS5317 Data Sheet Figure 4 Serial Data Timing
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
two modes which use the phase locked loop will require appropriate low pass filter components on the Evaluation Board. The low pass filter components help determine the PLL control loop response, including its bandwidth and stability and therefore directly affect the transient response of the PLL control loop. Appropriate filter components should be installed if a particular dynamic response to changes of the CLKIN signal is desired. The filter components which are installed on the board have been chosen for the following parameters: MODE: CLKG2; CLKIN: 7,200; N=512; damping factor: 1.0; Control loop -3 dB bandwidth: 2262 radians/second. These parameters yield R as 10 k and C as 0.22 F for the filter components.
The analog signal to be digitized is input to the AIN BNC connector. The digital output words from the CS5317 are buffered by HEX inverters as shown in Figure 3. The buffered versions of the CLKOUT and DATA signals are available on the header connector P1 in Figure 6. The serial data signals out of the CS5317 are illustrated in Figure 4. If remote control of the DOE line is desired, the trace on the PC Board can be opened and a wire connection can be soldered to the DOE input line. Remote control of the RST line of the CS5317 is also available if desired. Figures 5 and 6 illustrate the serial to parallel shift registers including timing information. The DATA output signal from the CS5317 is input to the data input of the shift register. An inverted version of the CLKOUT signal is used to clock the DATA into the shift registers. The two 8-bit shift register ICs also include output latches. The rising edge
Serial Data Shifting Out
Parallel Data (D0-D15) Valid
Serial Data Shifting Out
Parallel Data Valid
DATA
DOUT
DRDY
DACK
Figure 5. Parallel Data Timing
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29
CDB5317 of the DOUT signal from the CS5317 is used to latch the data once it is input to the shift registers. The rising edge of DOUT is also used to toggle the DRDY flip flop (see Figure 3). The flip flop is used to signal a remote device whenever new data is latched into the output registers. The DRDY flip flop is reset whenever DACK occurs. A component layout of the CDB5317 board is illustrated in Figure 7.
CLKIN (fig. 2) CLKOUT2 (fig. 3)
TP4
VL C2
0.1 F
P1 CLKIN CLKOUT DATA D15 D14 D13 D12 D11 D10 D9
10 16 DATA1 (fig. 3) TP5 12 RST QH 7 6
74HC595
U2 LATCH CLK
QG QF QE QD QC
5
4 3 2 1
11 14
SHIFT CLK DIN
QB
QA GND OE 8 13 VL C3 10 16
15
D8
R3 10k
0.1 F
9
RST DOUT 74HC595
QH QG QF
7 6 5
D7 D6 D5 D4 D3 D2 D1 D0 DACK DRDY
U3
DOUT2 (fig. 3) CLKOUT (fig. 3) DATA (fig. 2) 12 11 14 LATCH CLK SHIFT CLK DIN GND 8
QE 4 QD 3 QC 2 QB 1 QA 15 13
DACK (fig. 3) DRDY (fig. 3)
Figure 6.
30
DS27DB3
CDB5317
Figure 7. Bird's Eye View
DS27DB3
31

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