250 kSPS, 6-Channel, Simultaneous
Sampling, Bipolar 16-/14-/12-Bit ADC
Data Sheet
AD7656/AD7657/AD7658
Rev. D
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FEATURES
6 independent ADCs
True bipolar analog inputs
Pin-/software-selectable ranges: ±10 V, ±5 V
Fast throughput rate: 250 kSPS
iCMOS process technology
Low power
140 mW at 250 kSPS with 5 V supplies
Wide input bandwidth
86.5 dB SNR at 50 kHz input frequency
On-chip reference and reference buffers
Parallel, serial, and daisy-chain interface modes
High speed serial interface
SPI-/QSPI™-/MICROWIRE™-/DSP-compatible
Standby mode: 100 µW maximum
64-lead LQFP
APPLICATIONS
Power line monitoring systems
Instrumentation and control systems
Multi-axis positioning systems
FUNCTIONAL BLOCK DIAGRAM
V
SS
DGND
V
DD
REF
CONVS T A CONVS T B CONVS T C
OUTPUT
DRIVERS
OUTPUT
DRIVERS
OUTPUT
DRIVERS
OUTPUT
DRIVERS
CONTROL
LOGIC
BUF
BUF
BUF
AGND
T/H
T/H
T/H
T/H
T/H
T/H
CLK
OSC
AV
CC
DV
CC
V1
V2
V3
V4
V5
V6
SER/PAR
CS
V
DRIVE
STBY
DOUT A
DOUT B
DOUT C
SCLK
RD
WR
DATA/
CONTROL
LINES
05020-001
AD7656/AD7657/AD7658
16-/14- /12-BI T SAR
16-/14- /12-BI T SAR
16-/14- /12-BI T SAR
16-/14- /12-BI T SAR
16-/14- /12-BI T SAR
16-/14- /12-BI T SAR
Figure 1.
GENERAL DESCRIPTION
The AD7656/AD7657/AD76581 contain six 16-/14-/12-bit,
fast, low power, successive approximation ADCs all in the one
package that is designed on the iCMOS™ process (industrial
CMOS). iCMOS is a process combining high voltage silicon
with submicron CMOS and complementary bipolar technol-
ogies. It enables the development of a wide range of high
performance analog ICs, capable of 33 V operation in a
footprint that no previous generation of high voltage parts
could achieve. Unlike analog ICs using conventional CMOS
processes, iCMOS components can accept bipolar input signals
while providing increased performance, which dramatically
reduces power consumption and package size.
The AD7656/AD7657/AD7658 feature throughput rates up
to 250 kSPS. The parts contain low noise, wide bandwidth,
track-and-hold amplifiers that can handle input frequencies
up to 12 MHz.
The conversion process and data acquisition are controlled
using CONVST signals and an internal oscillator. Three
CONVST pins allow independent, simultaneous sampling of
the three ADC pairs. The AD7656/AD7657/AD7658 all have
a high speed parallel and serial interface, allowing the devices
to interface with microprocessors or DSPs. In serial interface
mode, the parts have a daisy-chain feature that allows multiple
ADCs to connect to a single serial interface. The AD7656/
AD7657/AD7658 can accommodate true bipolar input signals
in the ±4 × VREF range and ±2 × VREF range. The AD7656/
AD7657/AD7658 also contain an on-chip 2.5 V reference.
PRODUCT HIGHLIGHTS
1. Six 16-/14-/12-bit, 250 kSPS ADCs on board.
2. Six true bipolar, high impedance analog inputs.
3. Parallel and high speed serial interfaces.
1 Protected by U.S. Patent No. 6,731,232.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 2 of 32
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
AD7656 .......................................................................................... 3
AD7657 .......................................................................................... 5
AD7658 .......................................................................................... 7
Timing Specifications .................................................................. 9
Absolute Maximum Ratings .......................................................... 10
Thermal Resistance .................................................................... 10
ESD Caution ................................................................................ 10
Pin Configuration and Function Descriptions ........................... 11
Typical Performance Characteristics ........................................... 14
Terminology .................................................................................... 18
Theory of Operation ...................................................................... 20
Converter Details ....................................................................... 20
ADC Transfer Function ............................................................. 21
Reference Section ....................................................................... 21
Typical Connection Diagram ................................................... 21
Driving the Analog Inputs ........................................................ 22
Interface Section ......................................................................... 22
Application Hints ........................................................................... 29
Layout .......................................................................................... 29
Power Supply Configuration..................................................... 29
Outline Dimensions ....................................................................... 30
Ordering Guide .......................................................................... 30
REVISION HISTORY
3/12—Rev. C to Rev D
Changes to Figure 26 ...................................................................... 22
8/10—Rev. B to Rev. C
Changes to t1 Unit in Table 4 ........................................................... 9
Changes to VDD to AVCC Rating in Table 5 .................................. 10
Added Power Supply Configuration Section .............................. 29
Added Figure 36 .............................................................................. 29
VDD to AVCC
1/10—Rev. A to Rev. B
Changes to Unit of DC Accuracy Parameter, Table 1 .................. 3
Changes to DC Accuracy Parameter, Table 2 ............................... 5
Changes to DC Accuracy Parameter, Table 3 ............................... 7
Changes to Terminology Section.................................................. 18
Updated Outline Dimensions ....................................................... 30
Changes to Ordering Guide .......................................................... 30
4/06—Rev. 0 to Rev. A
Added AD7657/AD7658 parts ......................................... Universal
Changes to Table 1 ............................................................................. 3
Changes to Table 5 .......................................................................... 10
3/06—Revision 0: Initial Version
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 3 of 32
SPECIFICATIONS
AD7656
VREF = 2.5 V internal/external, AVCC = 4.75 V to 5.25 V, DVCC = 4.75 V to 5.25 V, VDRIVE = 2.7 V to 5.25 V;
For ±4 × VREF range: VDD = 10 V to 16.5 V, VSS = −10 V to −16.5 V; For ±2 × VREF range: VDD = 5 V to 16.5 V, VSS = −5 V to −16.5 V;
fSAMPLE = 250 kSPS, TA = TMIN to TMAX, unless otherwise noted.1
Table 1.
Parameter
B Version
1
Y Version
1
Unit
Test Conditions/Comments
DYNAMIC PERFORMANCE fIN = 50 kHz sine wave
Signal-to-Noise + Distortion (SINAD)2 84 84 dB min
85.5 85.5 dB typ
Signal-to-Noise Ratio (SNR)2 85 85 dB min
86.5 86.5 dB typ
Total Harmonic Distortion (THD)2 −90 −90 dB max
−92 −92 dB typ VDD/VSS = ±5 V to ±10 V
−100
−100
dB typ
V
DD
/V
SS
= ±12 V to ±16.5 V
Peak Harmonic or Spurious Noise (SFDR)2 −100 −100 dB typ
Intermodulation Distortion (IMD)2 fa = 50 kHz, fb = 49 kHz
Second-Order Terms −112 −112 dB typ
Third-Order Terms −107 −107 dB typ
Aperture Delay
10
10
ns max
Aperture Delay Matching 4 4 ns max
Aperture Jitter 35 35 ps typ
Channel-to-Channel Isolation2 −100 −100 dB typ fIN on unselected channels up to 100 kHz
Full Power Bandwidth 12 12 MHz typ @ −3 dB
2 2 MHz typ @ −0.1 dB
DC ACCURACY
Resolution 16 16 Bits
No Missing Codes 15 14 Bits min
16
16
Bits min
@ 25°C
Integral Nonlinearity2 ±3 ±4.5 LSB max
±1 ±1 LSB typ
Positive Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.22% FSR typical
Positive Full-Scale Error Matching2 ±0.35 ±0.35 % FSR max
Bipolar Zero-Scale Error
2
±0.023
±0.023
% FSR max
±0.004% FSR typical
Bipolar Zero-Scale Error Matching2 ±0.038 ±0.038 % FSR max
Negative Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.22% FSR typical
Negative Full-Scale Error Matching2 ±0.35 ±0.35 % FSR max
ANALOG INPUT See Table 8 for min VDD/VSS for each range
Input Voltage Ranges ±4 × VREF ±4 × VREF V RNG bit/RANGE pin = 0
±2 × VREF ±2 × VREF V RNG bit/RANGE pin = 1
DC Leakage Current ±1 ±1 µA max
Input Capacitance3 10 10 pF typ ±4 × VREF range when in track
14
14
pF typ
±2 × V
REF
range when in track
REFERENCE INPUT/OUTPUT
Reference Input Voltage Range 2.5/3 2.5/3 V min/max
DC Leakage Current ±1 ±1 µA max
Input Capacitance3 18.5 18.5 pF typ REFEN/DIS = 1
Reference Output Voltage 2.49/2.51 2.49/2.51 V min/max
Long-Term Stability 150 150 ppm typ 1,000 hours
Reference Temperature Coefficient 25 25 ppm/°C max
6
6
ppm/°C typ
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 4 of 32
Parameter B Version1 Y Version1 Unit Test Conditions/Comments
LOGIC INPUTS
Input High Voltage (VINH) 0.7 × VDRIVE 0.7 × VDRIVE V min
Input Low Voltage (VINL) 0.3 × VDRIVE 0.3 × VDRIVE V max
Input Current (IIN) ±1 ±1 µA max Typically 10 nA, VIN = 0 V or VDRIVE
Input Capacitance (C
IN
)
3
10
10
pF max
LOGIC OUTPUTS
Output High Voltage (VOH) VDRIVE − 0.2 VDRIVE − 0.2 V min ISOURCE = 200 µA
Output Low Voltage (VOL) 0.2 0.2 V max ISINK = 200 µA
Floating-State Leakage Current ±1 ±1 µA max
Floating-State Output Capacitance3 10 10 pF max
Output Coding Twos complement
CONVERSION RATE
Conversion Time 3.1 3.1 µs max
Track-and-Hold Acquisition Time2, 3 550 550 ns max
Throughput Rate 250 250 kSPS Parallel interface mode only
POWER REQUIREMENTS
VDD 5/15 5/15 V nom min/max For 4 × VREF range, VDD = 10 V to 16.5 V
VSS −5/−15 −5/−15 V nom min/max For 4 × VREF range, VDD = −10 V to −16.5 V
AVCC 5 5 V nom
DVCC 5 5 V nom
VDRIVE 3/5 3/5 V nom min/max
ITOTAL Digital I/PS = 0 V or VDRIVE
Normal Mode (Static) 28 28 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VSS = −16.5 V
Normal Mode (Operational)
26
26
mA max
f
SAMPLE
= 250 kSPS, AV
CC
= DV
CC
= V
DRIVE
= 5.25 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VDD = 16.5 V, VSS = −16.5 V
ISS (Operational) 0.25 0.25 mA max VSS = −16.5 V, fSAMPLE = 250 kSPS
IDD (Operational) 0.25 0.25 mA max VDD = 16.5 V, fSAMPLE = 250 kSPS
Partial Power-Down Mode 7 7 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Full Power-Down Mode (STBY Pin) 80 80 µA max SCLK on or off, AVCC = DVCC = VDRIVE = 5.25 V,
VDD = 16.5 V, VSS = −16.5 V
Power Dissipation AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Normal Mode (Static) 143 143 mW max
Normal Mode (Operational) 140 140 mW max fSAMPLE = 250 kSPS
Partial Power-Down Mode 35 35 mW max
Full Power-Down Mode (STBY Pin) 100 100 µW max
1 Temperature ranges are as follows: B version is −40°C to +85°C and Y version is −40°C to +125°C.
2 See the Terminology section.
3 Sample tested during initial release to ensure compliance.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 5 of 32
AD7657
VREF = 2.5 V internal/external, AVCC = 4.75 V to 5.25 V, DVCC = 4.75 V to 5.25 V, VDRIVE = 2.7 V to 5.25 V;
For ±4 × VREF range: VDD = 10 V to 16.5 V, VSS = −10 V to −16.5 V; For ±2 × VREF range: VDD = 5 V to 16.5 V, VSS = −5 V to −16.5 V;
fSAMPLE = 250 kSPS, TA = TMIN to TMAX, unless otherwise noted.1
Table 2.
Parameter B Version1 Y Version1 Unit Test Conditions/Comments
DYNAMIC PERFORMANCE fIN = 50 kHz sine wave
Signal-to-Noise + Distortion (SINAD)2 81.5 81.5 dB min
Signal-to-Noise Ratio (SNR)2 82.5 82.5 dB min
83.5 83.5 dB typ
Total Harmonic Distortion (THD)2 −90 −89 dB max
−92 −92 dB typ
Peak Harmonic or Spurious Noise (SFDR)2 −100 −100 dB typ
Intermodulation Distortion (IMD)2 fa = 50 kHz, fb = 49 kHz
Second-Order Terms
−109
−109
dB typ
Third-Order Terms
−104
−104
dB typ
Aperture Delay 10 10 ns max
Aperture Delay Matching 4 4 ns max
Aperture Jitter 35 35 ps typ
Channel-to-Channel Isolation2 −100 −100 dB typ fIN on unselected channels up to 100 kHz
Full Power Bandwidth 12 12 MHz typ @ −3 dB
2 2 MHz typ @ −0.1 dB
DC ACCURACY
Resolution 14 14 Bits
No Missing Codes 14 14 Bits min
Integral Nonlinearity2 ±1.5 ±1.5 LSB max
±1 ±1 LSB typ
Positive Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.183% FSR typical
Positive Full-Scale Error Matching
2
±0.3
±0.3
% FSR max
Bipolar Zero-Scale Error
2
±0.0305
±0.0305
% FSR max
±0.015 % FSR typical
Bipolar Zero-Scale Error Matching2 ±0.0427 ±0.0427 % FSR max
Negative Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.183% FSR typical
Negative Full-Scale Error Matching2 ±0.3 ±0.3 % FSR max
ANALOG INPUT See Table 8 for min VDD/VSS for each range
Input Voltage Ranges ±4 × VREF ±4 × VREF V RNG bit/RANGE pin = 0
±2 × VREF ±2 × VREF V RNG bit/RANGE pin = 1
DC Leakage Current ±1 ±1 µA max
Input Capacitance3 10 10 pF typ ±4 × VREF range when in track
14 14 pF typ ±2 × VREF range when in track
REFERENCE INPUT/OUTPUT
Reference Input Voltage Range
2.5/3
2.5/3
V min/max
DC Leakage Current ±1 ±1 µA max
Input Capacitance3 18.5 18.5 pF typ REFEN/DIS = 1
Reference Output Voltage 2.49/2.51 2.49/2.51 V min/max
Long-Term Stability 150 150 ppm typ 1,000 hours
Reference Temperature Coefficient 25 25 ppm/°C max
6 6 ppm/°C typ
LOGIC INPUTS
Input High Voltage (VINH) 0.7 × VDRIVE 0.7 × VDRIVE V min
Input Low Voltage (VINL) 0.3 × VDRIVE 0.3 × VDRIVE V max
Input Current (IIN) ±1 ±1 µA max Typically 10 nA, VIN = 0 V or VDRIVE
Input Capacitance (CIN)3 10 10 pF max
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 6 of 32
Parameter B Version1 Y Version1 Unit Test Conditions/Comments
LOGIC OUTPUTS
Output High Voltage (VOH) VDRIVE − 0.2 VDRIVE − 0.2 V min ISOURCE = 200 µA
Output Low Voltage (VOL) 0.2 0.2 V max ISINK = 200 µA
Floating-State Leakage Current ±1 ±1 µA max
Floating-State Output Capacitance
3
10
10
pF max
Output Coding Twos complement
CONVERSION RATE
Conversion Time 3.1 3.1 µs max
Track-and-Hold Acquisition Time2, 3 550 550 ns max
Throughput Rate 250 250 kSPS Parallel interface mode only
POWER REQUIREMENTS
VDD 5/15 5/15 V nom min/max For 4 × VREF range, VDD = 10 V to 16.5 V
VSS −5/−15 −5/−15 V nom min/max For 4 × VREF range, VDD = −10 V to −16.5 V
AVCC 5 5 V nom
DVCC 5 5 V nom
V
DRIVE
3/5
3/5
V nom min/max
ITOTAL Digital I/PS = 0 V or VDRIVE
Normal Mode (Static) 28 28 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VSS = −16.5 V
Normal Mode (Operational) 26 26 mA max fSAMPLE = 250 kSPS, AVCC = DVCC = VDRIVE = 5.25 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VDD = 16.5 V, VSS = −16.5 V
ISS (Operational) 0.25 0.25 mA max VSS = −16.5 V, fSAMPLE = 250 kSPS
IDD (Operational) 0.25 0.25 mA max VDD = 16.5 V, fSAMPLE = 250 kSPS
Partial Power-Down Mode 7 7 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Full Power-Down Mode (STBY Pin) 80 80 µA max SCLK on or off, AVCC = DVCC = VDRIVE = 5.25 V,
VDD = 16.5 V, VSS = −16.5 V
Power Dissipation AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Normal Mode (Static) 143 143 mW max
Normal Mode (Operational) 140 140 mW max fSAMPLE = 250 kSPS
Partial Power-Down Mode 35 35 mW max
Full Power-Down Mode (
STBY
Pin)
100
100
µW max
1 Temperature ranges are as follows: B version is −40°C to +85°C and Y version is −40°C to +125°C.
2 See the Terminology section.
3 Sample tested during initial release to ensure compliance.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 7 of 32
AD7658
VREF = 2.5 V internal/external, AVCC = 4.75 V to 5.25 V, DVCC = 4.75 V to 5.25 V, VDRIVE = 2.7 V to 5.25 V;
For ±4 × VREF range: VDD = 10 V to 16.5 V, VSS = −10 V to −16.5 V; For ±2 × VREF range: VDD = 5 V to 16.5 V, VSS = −5 V to −16.5 V;
fSAMPLE = 250 kSPS, TA = TMIN to TMAX, unless otherwise noted.1
Table 3.
Parameter B Version1 Y Version1 Unit Test Conditions/Comments
DYNAMIC PERFORMANCE fIN = 50 kHz sine wave
Signal-to-Noise + Distortion (SINAD)2 73 73 dB min
73.5 73.5 dB typ
Total Harmonic Distortion (THD)2 −88 −88 dB max
−92 −92 dB typ
Peak Harmonic or Spurious Noise (SFDR)2 −97 −97 dB typ
Intermodulation Distortion (IMD)2 fa = 50 kHz, fb = 49 kHz
Second-Order Terms −106 −106 dB typ
Third-Order Terms
−101
−101
dB typ
Aperture Delay
10
10
ns max
Aperture Delay Matching 4 4 ns max
Aperture Jitter 35 35 ps typ
Channel-to-Channel Isolation2 −100 −100 dB typ fIN on unselected channels up to 100 kHz
Full Power Bandwidth 12 12 MHz typ @ −3 dB
2 2 MHz typ @ −0.1 dB
DC ACCURACY
Resolution 12 12 Bits
No Missing Codes 12 12 Bits min
Differential Nonlinearity ±0.7 ±0.7 LSB max
Integral Nonlinearity2 ±1 ±1 LSB max
Positive Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.244% FSR typical
Positive Full-Scale Error Matching2 ±0.366 ±0.366 % FSR max
Bipolar Zero-Scale Error
2
±3
±3
LSB max
±0.0488% FSR typical
Bipolar Zero-Scale Error Matching
2
±3
±3
LSB max
Negative Full-Scale Error2 ±0.75 ±0.75 % FSR max ±0.244% FSR typical
Negative Full-Scale Error Matching2 ±0.366 ±0.366 % FSR max
ANALOG INPUT See Table 8 for min VDD/VSS for each range
Input Voltage Ranges ±4 × VREF ±4 × VREF V RNG bit/RANGE pin = 0
±2 × VREF ±2 × VREF V RNG bit/RANGE pin = 1
DC Leakage Current ±1 ±1 µA max
Input Capacitance3 10 10 pF typ ±4 × VREF range when in track
14 14 pF typ ±2 × VREF range when in track
REFERENCE INPUT/OUTPUT
Reference Input Voltage Range 2.5/3 2.5/3 V min/max
DC Leakage Current
±1
±1
µA max
Input Capacitance3 18.5 18.5 pF typ REFEN/DIS = 1
Reference Output Voltage 2.49/2.51 2.49/2.51 V min/max
Long-Term Stability 150 150 ppm typ 1,000 hours
Reference Temperature Coefficient 25 25 ppm/°C max
6 6 ppm/°C typ
LOGIC INPUTS
Input High Voltage (VINH) 0.7 × VDRIVE 0.7 × VDRIVE V min
Input Low Voltage (VINL) 0.3 × VDRIVE 0.3 × VDRIVE V max
Input Current (IIN) ±1 ±1 µA max Typically 10 nA, VIN = 0 V or VDRIVE
Input Capacitance (CIN)3 10 10 pF max
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 8 of 32
Parameter B Version1 Y Version1 Unit Test Conditions/Comments
LOGIC OUTPUTS
Output High Voltage (VOH) VDRIVE − 0.2 VDRIVE − 0.2 V min ISOURCE = 200 µA
Output Low Voltage (VOL) 0.2 0.2 V max ISINK = 200 µA
Floating-State Leakage Current ±1 ±1 µA max
Floating-State Output Capacitance
3
10
10
pF max
Output Coding Twos complement
CONVERSION RATE
Conversion Time 3.1 3.1 µs max
Track-and-Hold Acquisition Time2, 3 550 550 ns max
Throughput Rate 250 250 kSPS Parallel interface mode only
POWER REQUIREMENTS
VDD 5/15 5/15 V nom min/max For 4 × VREF range, VDD = 10 V to 16.5 V
VSS −5/−15 −5/−15 V nom min/max For 4 × VREF range, VDD = −10 V to −16.5 V
AVCC 5 5 V nom
DVCC 5 5 V nom
V
DRIVE
3/5
3/5
V nom min/max
ITOTAL Digital I/PS = 0 V or VDRIVE
Normal Mode (Static) 28 28 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VSS = −16.5 V
Normal Mode (Operational) 26 26 mA max fSAMPLE = 250 kSPS, AVCC = DVCC = VDRIVE = 5.25 V,
(Includes IAVCC, IVDD, IVSS, IVDRIVE, IDVCC) VDD = 16.5 V, VSS = −16.5 V
ISS (Operational) 0.25 0.25 mA max VSS = −16.5 V, fSAMPLE = 250 kSPS
IDD (Operational) 0.25 0.25 mA max VDD = 16.5 V, fSAMPLE = 250 kSPS
Partial Power-Down Mode 7 7 mA max AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Full Power-Down Mode (STBY Pin) 80 80 µA max SCLK on or off, AVCC = DVCC = VDRIVE = 5.25 V,
VDD = 16.5 V, VSS = −16.5 V
Power Dissipation AVCC = DVCC = VDRIVE = 5.25 V, VDD = 16.5 V,
VSS = −16.5 V
Normal Mode (Static) 143 143 mW max
Normal Mode (Operational) 140 140 mW max fSAMPLE = 250 kSPS
Partial Power-Down Mode 35 35 mW max
Full Power-Down Mode (
STBY
Pin)
100
100
µW max
1 Temperature ranges are as follows: B version is −40°C to +85°C and Y version is −40°C to +125°C
2 See the Terminology section.
3 Sample tested during initial release to ensure compliance.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 9 of 32
TIMING SPECIFICATIONS
AVCC/DVCC = 4.75 V to 5.25 V, VDD = 5 V to 16.5 V, VSS = −5 V to −16.5 V, V DRIVE = 2.7 V to 5.25 V, VREF = 2.5 V internal/external,
TA = TMIN to TMAX, unless otherwise noted.1
Table 4.
Parameter
Limit at TMIN, TMAX
Unit Description
VDRIVE < 4.75 V VDRIVE = 4.75 V to 5.25 V
PARALLEL MODE
tCONVERT 3 3 µs typ Conversion time, internal clock
tQUIET 150 150 ns min Minimum quiet time required between bus relinquish
and start of next conversion
tACQ 550 550 ns min Acquisition time
t10 25 25 ns min Minimum CONVST low pulse
t1 60 60 ns max CONVST high to BUSY high
tWAKE-UP 2 2 ms max STBY rising edge to CONVST rising edge
25 25 µs max Partial power-down mode
PARALLEL WRITE OPERATION
t11 15 15 ns min WR pulse width
t12 0 0 ns min CS to WR setup time
t13 5 5 ns min CS to WR hold time
t14 5 5 ns min Data setup time before WR rising edge
t15 5 5 ns min Data hold after WR rising edge
PARALLEL READ OPERATION
t2 0 0 ns min BUSY to RD delay
t3 0 0 ns min CS to RD setup time
t4 0 0 ns min CS to RD hold time
t5 45 36 ns min RD pulse width
t6 45 36 ns max Data access time after RD falling edge
t7 10 10 ns min Data hold time after RD rising edge
t
8
12
12
ns max
Bus relinquish time after
RD
rising edge
t9 6 6 ns min Minimum time between reads
SERIAL INTERFACE
fSCLK 18 18 MHz max Frequency of serial read clock
t16 12 12 ns max Delay from CS until SDATA three-state disabled
t172 22 22 ns max Data access time after SCLK rising edge/CS falling edge
t18 0.4 tSCLK 0.4 tSCLK ns min SCLK low pulse width
t19 0.4 tSCLK 0.4 tSCLK ns min SCLK high pulse width
t20 10 10 ns min SCLK to data valid hold time after SCLK falling edge
t21 18 18 ns max CS rising edge to SDATA high impedance
1 Sample tested during initial release to ensure compliance. All input signals are specified with tR = tF = 5 ns (10% to 90% of VDD) and timed from a voltage level of 1.6 V.
2 A buffer is used on the data output pins for this measurement.
200µA IOL
200µA IOH
1.6V
TO OUTPUT
PIN CL
25pF
05020-002
Figure 2. Load Circuit for Digital Output Timing Specification
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 10 of 32
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 5.
Parameter Rating
VDD to AGND, DGND −0.3 V to +16.5 V
VSS to AGND, DGND +0.3 V to −16.5 V
VDD to AVCC AVCC − 0.3 V to 16.5 V
AVCC to AGND, DGND −0.3 V to +7 V
DVCC to AVCC −0.3 V to AVCC + 0.3 V
DVCC to DGND, AGND −0.3 V to +7 V
AGND to DGND −0.3 V to +0.3 V
VDRIVE to DGND −0.3 V to DVCC + 0.3 V
Analog Input Voltage to AGND1 VSS − 0.3 V to VDD + 0.3 V
Digital Input Voltage to DGND −0.3 V to VDRIVE + 0.3 V
Digital Output Voltage to GND −0.3 V to VDRIVE + 0.3 V
REFIN to AGND −0.3 V to AVCC + 0.3 V
Input Current to Any Pin Except
Supplies2 ±10 mA
Operating Temperature Range
B Version −40°C to +85°C
Y Version −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Junction Temperature 150°C
Pb/SN Temperature, Soldering
Reflow (10 sec to 30 sec) 240(+0)°C
Pb-Free Temperature, Soldering Reflow 260(+0)°C
1 If the analog inputs are being driven from alternative VDD and VSS supply
circuitry, a 240 Ω series resistor should be placed on the analog inputs.
2 Transient currents of up to 100 mA do not cause SCR latch-up.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages. These
specifications apply to a four-layer board.
Table 6. Thermal Resistance
Package Type
θ
JA
θ
JC
Unit
64-Lead LQFP
45
11
°C/W
ESD CAUTION
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 11 of 32
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
64
DB15
63
WR/REF
EN/DIS
62
H/S SEL
61
SER/PAR/SEL
60
AV
CC
59
AGND
58
REFCAPC
57
AGND
56
REFCAPB
55
AGND
54
REFCAPA
53
AGND
52
AGND
51
REFIN/REFOUT
50
AV
CC
49
AGND
47
AV
CC
46
AV
CC
45
V5
42
V4
43
AGND
44
AGND
48
V6
41
AV
CC
40
AV
CC
39
V3
37
AGND
36
V2
35
AV
CC
34
AV
CC
33
V1
38
AGND
2
DB13
3
DB12
4
DB11
7
DB8/DOUT A
6
DB9/DOUT B
5
DB10/DOUT C
1
DB14/REFBUF
EN/DIS
8
DGND
9
V
DRIVE
10
DB7/HBEN/DCEN
12
DB5/DCIN A
13
DB4/DCIN B
14
DB3/DCIN C
15
DB2/SEL C
16
DB1/SEL B
11
DB6/SCLK
17
DB0/SEL A
18
BUSY
19
CS
20
RD
21
CONV S T C
22
CONV S T B
23
CONVST A
24
STBY
25
DGND
26
DV
CC
27
RANGE
28
RESET
29
W/B
30
V
SS
31
V
DD
32
AGND
PIN 1
AD7656/AD7657/AD7658
TOP VI EW
(No t t o Scal e)
05020-003
Figure 3. Pin Configuration
Table 7. Pin Function Descriptions
Pin No. Mnemonic Description
54, 56, 58
REFCAPA, REFCAPB,
REFCAPC
Decoupling capacitors are connected to these pins. This decouples the reference buffer for each
ADC pair. Each REFCAP pin should be decoupled to AGND using 10 µF and 100 nF capacitors.
33, 36, 39,
42, 45, 48
V1 to V6 Analog Input 1 to 6. These are six single-ended analog inputs. In hardware mode, the analog input
range on these channels is determined by the RANGE pin. In software mode, it is determined by
Bit RNGC to Bit RNGA of the control register (see Table 10).
32, 37, 38, 43,
44, 49, 52, 53,
55, 57, 59
AGND Analog Ground. Ground reference point for all analog circuitry on the AD7656/AD7657/AD7658.
All analog input signals and any external reference signal should be referred to this AGND voltage.
All 11 of these AGND pins should be connected to the AGND plane of a system. The AGND and
DGND voltages should ideally be at the same potential and must not be more than 0.3 V apart,
even on a transient basis.
26 DVCC Digital Power, 4.75 V to 5.25 V. The DVCC and AVCC voltages should ideally be at the same potential
and must not be more than 0.3 V apart, even on a transient basis. This supply should be decoupled
to DGND, and 10 µF and 100 nF decoupling capacitors should be placed on the DVCC pin.
9 VDRIVE Logic Power Supply Input. The voltage supplied at this pin determines the operating voltage of
the interface. Nominally at the same supply as the supply of the host interface. This pin should be
decoupled to DGND, and 10 µF and 100 nF decoupling capacitors should be placed on the VDRIVE pin.
8, 25 DGND Digital Ground. This is the ground reference point for all digital circuitry on the AD7656/AD7657/AD7658.
Both DGND pins should connect to the DGND plane of a system. The DGND and AGND voltages should
ideally be at the same potential and must not be more than 0.3 V apart, even on a transient basis.
34, 35, 40,
41, 46, 47,
50, 60
AVCC Analog Supply Voltage, 4.75 V to 5.25 V. This is the supply voltage for the ADC cores. The AVCC and
DVCC voltages should ideally be at the same potential and must not be more than 0.3 V apart, even
on a transient basis. These supply pins should be decoupled to AGND, and 10 µF and 100 nF
decoupling capacitors should be placed on the AVCC pins.
23, 22, 21 CONVST A,
CONVST B, CONVST C
Conversion Start Input A, B, C. These logic inputs are used to initiate conversions on the ADC pairs.
CONVST A is used to initiate simultaneous conversions on V1 and V2. CONVST B is used to initiate
simultaneous conversions on V3 and V4. CONVST C is used to initiate simultaneous conversions on
V5 and V6. When CONVSTx switches from low to high, the track-and-hold switch on the selected
ADC pair switches from track to hold and the conversion is initiated. These inputs can also be used
to place the ADC pairs into partial power-down mode.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 12 of 32
Pin No. Mnemonic Description
19 CS Chip Select. This active low logic input frames the data transfer. When both CS and RD are logic low
in parallel mode, the output bus is enabled and the conversion result is output on the parallel data
bus lines. When both CS and WR are logic low in parallel mode, DB[15:8] are used to write data to
the on-chip control register. In serial mode, the CS is used to frame the serial read transfer and clock
out the MSB of the serial output data.
20 RD Read Data. When both CS and RD are logic low in parallel mode, the output bus is enabled. In serial
mode, the RD line should be held low.
63 WR/REFEN/
DIS Write Data/Reference Enable/Disable. When H/S SEL pin is high and both CS and WR are logic low,
DB[15:8] are used to write data to the internal control register. When the H/S SEL pin is low, this pin
is used to enable or disable the internal reference. When H/S SEL = 0 and REFEN/DIS = 0, the internal
reference is disabled and an external reference should be applied to the REFIN/REFOUT pin. When
H/S SEL = 0 and REFEN/DIS = 1, the internal reference is enabled and the REFIN/REFOUT pin should be
decoupled. See the Reference Section.
18 BUSY BUSY Output. This pin transitions high when a conversion is started and remains high until the
conversion is complete and the conversion data is latched into the output data registers. A new
conversion should not be initiated on the AD7656/AD7657/AD7658 when the BUSY signal is high.
51 REFIN/REFOUT Reference Input/Output. The on-chip reference is available on this pin for use external to the
AD7656/AD7657/AD7658. Alternatively, the internal reference can be disabled and an external
reference can be applied to this input. See the Reference Section. When the internal reference is
enabled, this pin should be decoupled using at least a 10 µF decoupling capacitor.
61 SER/PAR/SEL Serial/Parallel Selection Input. When this pin is low, the parallel interface is selected. When this
pin is high, the serial interface mode is selected. In serial mode, DB[10:8] take on their DOUT[C:A]
function, DB[0:2] take on their DOUT select function, DB7 takes on its DCEN function. In serial mode,
DB15 and DB[13:11] should be tied to DGND.
17 DB0/SEL A Data Bit 0/Select DOUT A. When SER/PAR = 0, this pin acts as a three-state parallel digital output pin.
When SER/PAR = 1, this pin takes on its SEL A function; it is used to configure the serial interface. If
this pin is 1, the serial interface operates with one/two/three DOUT output pins and enables DOUT A
as a serial output. When operating in serial mode, this pin should always be = 1.
16 DB1/SEL B Data Bit 1/Select DOUT B. When SER/PAR = 0, this pin acts as a three-state parallel digital output pin.
When SER/PAR = 1, this pin takes on its SEL B function; it is used to configure the serial interface. If
this pin is 1, the serial interface operates with two/three DOUT output pins and enables DOUT B as a
serial output. If this pin is 0, the DOUT B is not enabled to operate as a serial data output pin and
only one DOUT output pin, DOUT A, is used. Unused serial DOUT pins should be left unconnected.
15 DB2/SEL C Data Bit 2/Select DOUT C. When SER/PAR = 0, this pin acts as a three-state parallel digital output pin.
When SER/PAR = 1, this pin takes on its SEL C function; it is used to configure the serial interface. If
this pin is 1, the serial interface operates with three DOUT output pins and enables DOUT C as a
serial output. If this pin is 0, the DOUT C is not enabled to operate as a serial data output pin.
Unused serial DOUT pins should be left unconnected.
14 DB3/DCIN C Data Bit 3/Daisy-Chain Input C. When SER/PAR = 0, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and DCEN = 1, this pin acts as Daisy-Chain Input C. When operating
in serial mode but not in daisy-chain mode, this pin should be tied to DGND.
13 DB4/DCIN B Data Bit 4/Daisy-Chain Input B. When SER/PAR = 0, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and DCEN = 1, this pin acts as Daisy-Chain Input B. When operating
in serial mode but not in daisy-chain mode, this pin should be tied to DGND.
12 DB5/DCIN A Data Bit 5/Daisy-Chain Input A. When SER/PAR is low, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and DCEN = 1, this pin acts as Daisy-Chain Input A. When operating
in serial mode but not in daisy-chain mode, this pin should be tied to DGND.
11 DB6/SCLK Data Bit 6/Serial Clock. When SER/PAR = 0, this pin acts as a three-state parallel digital output pin. When
SER/PAR = 1, this pin takes on its SCLK input function; it is the read serial clock for the serial transfer.
10 DB7/HBEN/DCEN Data Bit 7/High Byte Enable/Daisy-Chain Enable. When operating in parallel word mode
(SER/PAR = 0 and W/B = 0), this pin takes on its Data Bit 7 function. When operating in parallel
byte mode (SER/PAR = 0 and W/B = 1), this pin takes on its HBEN function. When in this mode and
the HBEN pin is logic high, the data is output MSB byte first on DB[15:8]. When the HBEN pin is
logic low, the data is output LSB byte first on DB[15:8]. When operating in serial mode (SER/PAR = 1),
this pin takes on its DCEN function. When the DCEN pin is logic high, the parts operate in daisy-
chain mode with DB[5:3] taking on their DCIN[A:C] function. When operating in serial mode but
not in daisy-chain mode, this pin should be tied to DGND.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 13 of 32
Pin No. Mnemonic Description
7 DB8/DOUT A Data Bit 8/Serial Data Output A. When SER/PAR = 0, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and SEL A = 1, this pin takes on its DOUT A function and outputs
serial conversion data.
6 DB9/DOUT B Data Bit 9/Serial Data Output B. When SER/PAR = 0, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and SEL B = 1, this pin takes on its DOUT B function and outputs
serial conversion data. This configures the serial interface to have two DOUT output lines.
5 DB10/DOUT C Data Bit 10/Serial Data Output C. When SER/PAR = 0, this pin acts as a three-state parallel digital
output pin. When SER/PAR = 1 and SEL C = 1, this pin takes on its DOUT C function and outputs
serial conversion data. This configures the serial interface to have three DOUT output lines.
4 DB11 Data Bit 11/Digital Ground. When SER/PAR = 0, this pin acts as a three-state parallel digital output
pin. When SER/PAR = 1, this pin should be tied to DGND.
3, 2, 64 DB12, DB13, DB15 Data Bit 12, Data Bit 13, Data Bit 15. When SER/PAR = 0, these pins act as three-state parallel digital
input/output pins. When CS and RD are low, these pins are used to output the conversion result.
When CS and WR are low, these pins are used to write to the control register. When SER/PAR = 1,
these pins should be tied to DGND. For the AD7657, DB15 contains a leading zero. For the AD7658,
DB15, DB13, and DB12 contain leading zeros.
1 DB14/REFBUFEN/DIS Data Bit 14/REFBUF Enable/Disable. When SER/PAR = 0, this pin acts as a three-state digital input/
output pin. For the AD7657/AD7658, DB14 contains a leading zero. When SER/PAR = 1, this pin can be
used to enable or disable the internal reference buffers.
28 RESET Reset Input. When set to logic high, this pin resets the AD7656/AD7657/AD7658. The current
conversion, if any, is aborted. The internal register is set to all 0s. In hardware mode, the
AD7656/AD7657/AD7658 are configured depending on the logic levels on the hardware select pins.
In all modes, the parts should receive a RESET pulse after power-up. The reset high pulse should be
typically 100 ns wide. After the RESET pulse, the AD7656/AD7657/AD7658 needs to see a valid
CONVST pulse to initiate a conversion; this should consist of a high-to-low CONVST edge followed
by a low-to-high CONVST edge. The CONVST signal should be high during the RESET pulse.
27 RANGE Analog Input Range Selection. Logic input. The logic level on this pin determines the input range of
the analog input channels. When this pin is Logic 1 at the falling edge of BUSY, the range for the
next conversion is ±2 × VREF. When this pin is Logic 0 at the falling edge of BUSY, the range for the
next conversion is ±4 × VREF. In hardware select mode, the RANGE pin is checked on the falling edge
of BUSY. In software mode (H/S SEL = 1), the RANGE pin can be tied to DGND and the input range is
determined by the RNGA, RNGB, and RNGC bits in the control register.
31 VDD Positive Power Supply Voltage. This is the positive supply voltage for the analog input section, and
10 µF and 100 nF decoupling capacitors should be placed on the VDD pin.
30 VSS Negative Power Supply Voltage. This is the negative supply voltage for the analog input section, and
10 µF and 100 nF decoupling capacitors should be placed on the VSS pin.
24 STBY Standby Mode Input. This pin is used to put all six on-chip ADCs into standby mode. The STBY pin is
high for normal operation and low for standby operation.
62 H/S SEL Hardware/Software Select Input. Logic input. When H/S SEL = 0, the AD7656/AD7657/AD7658
operate in hardware select mode, and the ADC pairs to be simultaneously sampled are selected
by the CONVST pins. When H/S SEL = 1, the ADC pairs to be sampled simultaneously are selected by
writing to the control register. In serial mode, CONVST A is used to initiate conversions on the
selected ADC pairs.
29 W/B Word/Byte Input. When this pin is logic low, data can be transferred to and from the AD7656/AD7657/
AD7658 using the parallel data lines DB[15:0]. When this pin is logic high, byte mode is enabled. In this
mode, data is transferred using data lines DB[15:8] and DB[7] takes on its HBEN function. To obtain the
16-bit conversion result, 2-byte reads are required. In serial mode, this pin should be tied to DGND.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 14 of 32
TYPICAL PERFORMANCE CHARACTERISTICS
0
–160 0
FRE QUENCY ( kHz )
(dB)
125
05020-030
–20
–40
–60
–80
–100
–120
–140
25 50 75 100
V
DD
/V
SS
= ±15V
AV
CC
/DV
CC
/V
DRIVE
= +5V
INTERNAL RE FERENCE
±10V RANG E
T
A
= 25° C
f
S
= 250kSPS
f
IN
= 50kHz
SNR = +87.33d B
SI NAD = + 87.251d B
THD = –104.32d B
SF DR = –104.13d B
Figure 4. AD7656 FFT for ±10 V Range
0
–160 0
FRE QUENCY ( kHz )
(dB)
125
05020-031
–20
–40
–60
–80
–100
–120
–140
25 50 75 100
V
DD
/V
SS
= ±12V
AV
CC
/DV
CC
/V
DRIVE
= +5V
INTERNAL RE FERENCE
±5V RANG E
T
A
= 25° C
f
S
= 250kSPS
f
IN
= 50kHz
SNR = +86.252d B
SI NAD = + 86.196d B
THD = –105.11d B
SF DR = –98.189d B
Figure 5. AD7656 FFT for ±5 V Range
2.0
–2.0 010k 20k 30k 40k 50k 60k 65535
05020-017
CODE
INL (LSB)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
f
SAMPLE
= 250kSPS
2 × V
REF
RANGE
INL WCP = 0.64LS B
INL WCN = –0.76LS B
Figure 6. AD7656 Typical INL
2.0
–2.0 010k 20k 30k 40k 50k 60k 65535
05020-016
CODE
DNL ( LSB)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
f
SAMPLE
= 250kSPS
2 × V
REF
RANGE
DNL WCP = 0.81LS B
DNL WCN = –0. 57LSB
Figure 7. AD7656 Typical DNL
02000 4000 6000 8000 10000 12000 14000 16383
05020-035
INL (LSB)
CODE
2.0
–2.0
1.6
0.8
0
–0.8
–1.6
1.2
0.4
–0.4
–1.2
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
f
SAMPLE
= 250kSPS
2 × V
REF
RANGE
Figure 8. AD7657 Typical INL
2.0
–2.0
1.6
0.8
0
–0.8
–1.6
1.2
0.4
–0.4
–1.2
02000 4000 6000 8000 10000 12000 14000 16383
DNL ( LSB)
CODE
05020-034
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
Figure 9. AD7657 Typical DNL
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 15 of 32
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0 0500 1000 1500 2000 2500 3000 3500 4095
05020-033
INL (LSB)
CODE
AVCC/DVCC/VDRIVE = +5V
VDD/VSS = ± 12V
f
SAMPLE = 250kS P S
2 × VREF RANG E
Figure 10. AD7658 Typical INL
05020-032
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0 0500 1000 1500 2000 2500 3000 3500 4095
DNL ( LSB)
CODE
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
fSAMPLE
= 250kSPS
2 × V
REF
RANGE
Figure 11. AD7658 Typical DNL
90
6010 1000
05020-023
ANALOG INPUT FREQUENCY ( kHz )
SI NAD ( dB)
100
85
80
75
70
65
AV
CC
/DV
CC
/V
DRIVE
= +5. 25V
V
DD
/V
SS
= ±16. 5V
±10V RANG E
AV
CC
/DV
CC
/
V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
±5V RANG E
AV
CC
/DV
CC
/
V
DRIVE
= +5V
V
DD
/V
SS
= ±5. 25V
±5V RANG E
AV
CC
/DV
CC
/
V
DRIVE
= +4. 75 V
V
DD
/V
SS
= ±10V
±10V RANG E
f
SAMPLE
= 250kSPS
INTERNAL RE FERENCE
T
A
= 25° C
Figure 12. AD7656 SINAD vs. Input Frequency
–60
–12010 1000
05020-022
ANALOG INPUT FREQUENCY ( kHz )
THD ( dB)
100
–70
–80
–90
–100
–110
AV
CC
/DV
CC
/
V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
±5V RANG E
AV
CC
/DV
CC
/
V
DRIVE
= +5. 25V
V
DD
/V
SS
= ±16. 5V
±10V RANG E
f
SAMPLE
= 250kSPS
INTERNAL RE FERENCE
T
A
= 25° C AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±5. 25V
±5V RANG E
AV
CC
/DV
CC
/
V
DRIVE
= +4. 75V
V
DD
/V
SS
= ±10V
±10V RANG E
Figure 13. AD7656 THD vs. Input Frequency
–60
–12010 100
05020-026
ANALOG INPUT FREQUENCY ( kHz )
THD ( dB)
–70
–80
–90
–100
–110
V
DD
/V
SS
= ±16. 5V
AV
CC
/DV
CC
/V
DRIVE
= +5. 25V
T
A
= 25° C
INTERNAL RE FERENCE
±4 × V
REF
RANGE
R
SOURCE
= 1000Ω
R
SOURCE
= 10Ω
R
SOURCE
= 100Ω
R
SOURCE
= 50Ω
R
SOURCE
= 220Ω
Figure 14. AD7656 THD vs. Input Frequency for Various Source Impedances,
±4 × VREF Range
–40
–12010 100
05020-027
ANALOG INPUT FREQUENCY ( kHz )
THD ( dB)
–50
–60
–70
–80
–90
–100
–110
V
DD
/V
SS
= ±12V
AV
CC
/DV
CC
/V
DRIVE
= +5V
T
A
= 25° C
INTERNAL RE FERENCE
±2 × V
REF
RANGE
R
SOURCE
= 1000Ω
R
SOURCE
= 100Ω
R
SOURCE
= 50Ω
R
SOURCE
= 220Ω
R
SOURCE
= 10Ω
Figure 15. AD7656 THD vs. Input Frequency for Various Source Impedances,
±2 × VREF Range
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 16 of 32
–55 125
05020-018
TEMPERATURE (°C)
REFERENCE VOLT AGE (V)
–35 –15 525 45 65 85 105
2.492
2.494
2.496
2.498
2.500
2.502
2.504
2.506
2.508
2.510 AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
Figure 16. Reference Voltage vs. Temperature
3.20
2.70
–55 125
05020-019
TEMPERATURE (°C)
CONVERSION TIME (µs)
3.15
3.10
3.05
3.00
2.95
2.90
2.85
2.80
2.75
–35 –15 525 45 65 85 105
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
Figure 17. Conversion Time vs. Temperature
3500
–5
CODE
NUMBER OF OCCURRENCE S
3
3000
2500
2000
1500
1000
500
–4 –3 –2 –1 012
VDD/VSS = ± 15V
AVCC/DVCC/VDRIVE = +5V
INTERNAL RE FERENCE
8192 SAMP LES
05020-029
25
168
1532
3212
2806
392
57 0
0
0
Figure 18. AD7656 Histogram of Codes
100
4030 530
05020-021
SUPPLY RIPPLE FREQUENCY (kHz)
PSRR ( dB)
90
80
70
60
50
80 130 180 230 280 330 380 430 480
V
DD
V
SS
f
SAMPLE
= 250kSPS
±2 × V
REF
RANGE
INTERNAL RE FERENCE
T
A
= 25° C
f
IN
= 10kHz
100nF ON V
DD
AND V
SS
Figure 19. PSRR vs. Supply Ripple Frequency
–40 140
05020-025
TEMPERATURE (°C)
SNR (dB)
–20 020 40 60 80 100 120
83.0
83.5
84.0
84.5
85.0
85.5
86.0
86.5
87.0
±5V RANG E ,
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
f
SAMPLE
= 250kSPS
f
IN
= 50kHz
INTERNAL RE FERENCE
±10V RANG E ,
AV
CC
/DV
CC
/V
DRIVE
= +5. 25V
V
DD
/V
SS
= ±16. 5V
Figure 20. AD7656 SNR vs. Temperature
–100
–107
–40 140
05020-024
TEMPERATURE (°C)
THD ( dB)
–101
–102
–103
–104
–105
–106
–20 020 40 60 80 100 120
±10V RANG E ,
AV
CC
/DV
CC
/V
DRIVE
= +5. 25V
V
DD
/V
SS
= ±16. 5V
±5V RANG E ,
AV
CC
/DV
CC
/V
DRIVE
= +5V
V
DD
/V
SS
= ±12V
f
SAMPLE
= 250kSPS
f
IN
= 50kHz
INTERNAL RE FERENCE
Figure 21. AD7656 THD vs. Temperature
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 17 of 32
120
600
05020-028
FRE QUENCY OF INPUT NOISE ( kHz )
CHANNEL - TO- CHANNE L I S OLATI ON (d B)
AV
CC
/DV
CC
/V
DRIVE
= 5V
V
DD
/V
SS
= ±12V
T
A
= 25° C
INTERNAL RE FERENCE
±2 × V
REF
RANGE
30kHz O N S E LECT E D CHANNE L
110
100
90
80
70
20 40 60 80 100 120 140
Figure 22. Channel-to-Channel Isolation
30
0
–40 100
05020-020
TEMPERATURE (°C)
DYNAMIC CURRENT ( mA)
25
20
15
10
5
–20 020 40 60 80
±10V RANG E
±5V RANG E
AV
CC
/DV
CC
/V
DRIVE
= +5V
f
SAMPLE
= 250kSPS
FOR ±5V RANGE V
DD
/V
SS
= ±12V
FOR ±10V RANGE V
DD
/V
SS
= ±16. 5V
Figure 23. Dynamic Current vs. Temperature
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 18 of 32
TERMINOLOGY
Integral Nonlinearity
The maximum deviation from a straight line passing through
the endpoints of the ADC transfer function. The endpoints of
the transfer function are zero scale, a ½ LSB below the first code
transition and full scale at ½ LSB above the last code transition.
Differential Nonlinearity
The difference between the measured and the ideal 1 LSB
change between any two adjacent codes in the ADC.
Bipolar Zero Code Error
The deviation of the midscale transition (all 1s to all 0s) from
the ideal VIN voltage, that is, AGND − 1 LSB.
Bipolar Zero Code Error Matching
The difference in bipolar zero code error between any two input
channels.
Positive Full-Scale Error
The deviation of the last code transition (011…110) to (011…111)
from the ideal (+4 × VREF − 1 LSB, +2 × VREF − 1 LSB) after
adjusting for the bipolar zero code error.
Positive Full-Scale Error Matching
The difference in positive full-scale error between any two input
channels.
Negative Full-Scale Error
The deviation of the first code transition (10…000) to (10…001)
from the ideal (−4 × VREF + 1 LSB, −2 × VREF + 1 LSB) after
adjusting for the bipolar zero code error.
Negative Full-Scale Error Matching
The difference in negative full-scale error between any two
input channels.
Track-and-Hold Acquisition Time
The track-and-hold amplifier returns to track mode at the end
of the conversion. The track-and-hold acquisition time is the
time required for the output of the track-and-hold amplifier to
reach its final value, within ±1 LSB, after the end of the conversion.
See the Track-and-Hold Section for more details.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the measured output signal
to the rms sum of all other spectral components below the
Nyquist frequency. The value for SNR is expressed in decibels.
Signal-to-(Noise + Distortion) Ratio (SINAD)
The measured ratio of signal-to-(noise + distortion) at the
output of the ADC. The signal is the rms amplitude of the
fundamental. Noise is the sum of all nonfundamental signals up
to half the sampling frequency (fS/2, excluding dc).
The ratio depends on the number of quantization levels in the
digitization process: the more levels, the smaller the quantization
noise. The theoretical signal-to-(noise + distortion) ratio for an
ideal N-bit converter with a sine wave input is given by
Signal-to-(Noise + Distortion) = (6.02 N + 1.76) dB
Thus, this is 98 dB for a 16-bit converter, 86.04 dB for a 14-bit
converter, and 74 dB for a 12-bit converter.
Total Harmonic Distortion (THD)
The ratio of the rms sum of the harmonics to the fundamental.
For the AD7656/AD7657/AD7658, it is defined as
1
2
6
2
5
2
4
2
3
2
2
log20)dB(V
VVVVV
THD
++++
=
where:
V1 is the rms amplitude of the fundamental.
V2, V3, V4, V5, and V6 are the rms amplitudes of the second
through sixth harmonics.
Peak Harmonic or Spurious Noise (SFDR)
The ratio of the rms value of the next largest component in the
ADC output spectrum (up to fS/2, excluding dc) to the rms value
of the fundamental. Normally, the value of this specification is
determined by the largest harmonic in the spectrum, but for
ADCs where the harmonics are buried in the noise floor, it is
determined by a noise peak.
Intermodulation Distortion (IMD)
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities create distortion
products at sum and difference frequencies of mfa ± nfb, where
m, n = 0, 1, 2, 3. Intermodulation distortion terms are those for
which neither m nor n are equal to 0. For example, the second-
order terms include (fa + fb) and (fa − fb), and the third-order
terms include (2fa + fb), (2fa − fb), (fa + 2fb), and (fa − 2fb).
The AD7656/AD7657/AD7658 are tested using the CCIF standard
in which two input frequencies near the top end of the input
bandwidth are used. In this case, the second-order terms are
usually distanced in frequency from the original sine waves,
and the third-order terms are usually at a frequency close to the
input frequencies. As a result, the second- and third-order terms
are specified separately. The calculation of the intermodulation
distortion is per the THD specification, where it is the ratio of
the rms sum of the individual distortion products to the rms
amplitude of the sum of the fundamentals expressed in decibels.
Power Supply Rejection (PSR)
Variations in power supply affect the full-scale transition but
not the converter’s linearity. Power supply rejection is the
maximum change in full-scale transition point due to a change
in power supply voltage from the nominal value. See the Typical
Performance Characteristics section.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 19 of 32
Figure 19 shows the power supply rejection ratio vs. supply
ripple frequency for the AD7656/AD7657/AD7658.
The power supply rejection ratio is defined as the ratio
of the power in the ADC output at full-scale frequency, f,
to the power of a 200 mV p-p sine wave applied to the
ADC’s VDD and VSS supplies of frequency fS
PSRR (dB) = 10 log (Pf/PfS)
where:
Pf is equal to the power at frequency f in the ADC output.
PfS is equal to the power at frequency fS coupled onto the VDD
and VSS supplies.
Channel-to-Channel Isolation
Channel-to-channel isolation is a measure of the level of crosstalk
between any two channels. It is measured by applying a full-scale,
100 kHz sine wave signal to all unselected input channels and
determining the degree to which the signal attenuates in the
selected channel with a 30 kHz signal.
% FSR
%FSR is calculated using the full theoretical span of the ADC.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 20 of 32
THEORY OF OPERATION
CONVERTER DETAILS
The AD7656/AD7657/AD7658 are high speed, low power
converters that allow the simultaneous sampling of six on-chip
ADCs. The analog inputs on the AD7656/AD7657/AD7658 can
accept true bipolar input signals. The RANGE pin/RNG bits are
used to select either ±4 × VREF or ±2 × VREF as the input range
for the next conversion.
Each AD7656/AD7657/AD7658 contains six SAR ADCs, six
track-and-hold amplifiers, an on-chip 2.5 V reference, reference
buffers, and high speed parallel and serial interfaces. The parts
allow the simultaneous sampling of all six ADCs when all three
CONVST signals are tied together. Alternatively, the six ADCs
can be grouped into three pairs. Each pair has an associated
CONVST signal used to initiate simultaneous sampling on each
ADC pair, on four ADCs, or on all six ADCs. CONVST A is used
to initiate simultaneous sampling on V1 and V2, CONVST B
is used to initiate simultaneous sampling on V3 and V4, and
CONVST C is used to initiate simultaneous sampling on V5
and V6.
A conversion is initiated on the AD7656/AD7657/AD7658 by
pulsing the CONVST x input. On the rising edge of CONVST x,
the track-and-hold of the selected ADC pair is placed into hold
mode and the conversions are started. After the rising edge of
CONVST x, the BUSY signal goes high to indicate that the
conversion is taking place. The conversion clock for the
AD7656/AD7657/AD7658 is internally generated, and the
conversion time for the parts is 3 µs. The BUSY signal returns
low to indicate the end of conversion. On the falling edge of
BUSY, the track-and-hold returns to track mode. Data can be
read from the output register via the parallel or serial interface.
Track-and-Hold Section
The track-and-hold amplifiers on the AD7656/AD7657/AD7658
allow the ADCs to accurately convert an input sine wave of full-
scale amplitude to 16-/14-/12-bit resolution, respectively. The
input bandwidth of the track-and-hold amplifiers is greater
than the Nyquist rate of the ADC, even when the AD7656/
AD7657/AD7658 are operating at its maximum throughput
rate. The parts can handle input frequencies of up to 12 MHz.
The track-and-hold amplifiers sample their respective inputs
simultaneously on the rising edge of CONVSTx. The aperture time
for the track-and-hold (that is, the delay time between the external
CONVSTx signal actually going into hold) is 10 ns. This is well
matched across all six track-and-holds on one device and from
device to device. This allows more than six ADCs to be sampled
simultaneously. The end of the conversion is signaled by the falling
edge of BUSY, and it is at this point that the track-and-holds return
to track mode and the acquisition time begins.
Analog Input Section
The AD7656/AD7657/AD7658 can handle true bipolar input
voltages. The logic level on the RANGE pin or the value written
to the RNGx bits in the control register determines the analog
input range on the AD7656/AD7657/AD7658 for the next
conversion. When the RANGE pin/RNGx bit is 1, the analog
input range for the next conversion is ±2 × VREF. When the
RANGE pin/RNGx bit is 0, the analog input range for the next
conversion is ±4 × VREF.
D1
D2
V
DD
C2
R1
V1
V
SS
C1
05020-004
Figure 24. Equivalent Analog Input Structure
Figure 24 shows an equivalent circuit of the analog input structure
of the AD7656/AD7657/AD7658. The two diodes, D1 and D2,
provide ESD protection for the analog inputs. Care must be
taken to ensure that the analog input signal never exceeds the
VDD and VSS supply rails by more than 300 m V. Signals exceeding
this value cause these diodes to become forward-biased and to
start conducting current into the substrate. The maximum
current these diodes can conduct without causing irreversible
damage to the parts is 10 mA. Capacitor C1 in Figure 24 is
typically about 4 pF and can be attributed primarily to pin
capacitance. Resistor R1 is a lumped component made up of
the on resistance of a switch (track-and-hold switch). This
resistor is typically about 25 Ω. Capacitor C2 is the ADC
sampling capacitor and has a capacitance of 10 pF typically.
The AD7656/AD7657/AD7658 require VDD and VSS dual
supplies for the high voltage analog input structures. These
supplies must be equal to or greater than the analog input range
(see Table 8 for the requirements on these supplies for each
analog input range). The AD7656/AD7657/AD7658 require a
low voltage AVCC supply of 4.75 V to 5.25 V to power the ADC
core, a DVCC supply of 4.75 V to 5.25 V for the digital power,
and a VDRIVE supply of 2.7 V to 5.25 V for the interface power.
To meet the specified performance when using the minimum
supply voltage for the selected analog input range, it can be
necessary to reduce the throughput rate from the maximum
throughput rate.
Table 8. Minimum VDD/VSS Supply Voltage Requirements
Analog Input
Range (V)
Reference
Voltage (V)
Full-Scale
Input (V)
Minimum
VDD/VSS (V)
±4 × VREF +2.5 ±10 ±10
±4 × VREF +3.0 ±12 ±12
±2 × VREF +2.5 ±5 ±5
±2 × VREF +3.0 ±6 ±6
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 21 of 32
ADC TRANSFER FUNCTION
The output coding of the AD7656/AD7657/AD7658 is twos
complement. The designed code transitions occur midway
between successive integer LSB values, that is, 1/2 LSB, 3/2 LSB.
The LSB size is FSR/65536 for the AD7656, FSR/16384 for the
AD7657, and FSR/4096 for the AD7658. The ideal transfer
characteristic is shown in Figure 25.
011...111
011...110
000...001
000...000
111...111
–FS R/2 + 1/ 2LSB +FS R/2 – 3/ 2LSB
AGND – 1LSB
ANALOG INPUT
ADC CODE
100...010
100...001
100...000
05020-005
Figure 25. AD7656/AD7657/AD7658 Transfer Characteristic
The LSB size is dependent on the analog input range selected
(see Table 9).
REFERENCE SECTION
The RFIN/REFOUT pin either allows access to the AD7656/
AD7657/AD7658’s 2.5 V reference or it allows an external
reference to be connected, providing the reference source for
each part’s conversions. The AD7656/AD7657/AD7658 can
accommodate a 2.5 V to 3 V external reference range. When
using an external reference, the internal reference needs to be
disabled. After a reset, the AD7656/AD7657/AD7658 default to
operating in external reference mode with the internal reference
buffers enabled. The internal reference can be enabled in either
hardware or software mode. To enable the internal reference in
hardware mode, the H/S SEL pin = 0 and the REFEN/DIS pin = 1. To
enable the internal reference in software mode, H/S SEL = 1 and
a write to the control register is necessary to make DB9 of the
register = 1. For the internal reference mode, the REFIN/REFOUT
pin should be decoupled using 10 µF and 100 nF capacitors.
The AD7656/AD7657/AD7658 contain three on-chip reference
buffers. Each of the three ADC pairs has an associated reference
buffer. These reference buffers require external decoupling
capacitors on REFCAPA, REFCAPB, and REFCAPC pins,
and 10 µF and 100 nF decoupling capacitors should be placed
on these REFCAP pins. The internal reference buffers can be
disabled in software mode by writing to Bit DB8 in the internal
control register. If operating the devices in serial mode,
the internal reference buffers can be disabled in hardware
mode by setting the DB14/REFBUFEN/DIS pin high. If the
internal reference and its buffers are disabled, an external
buffered reference should be applied to the REFCAP pins.
TYPICAL CONNECTION DIAGRAM
Figure 26 shows the typical connection diagram for the
AD7656/AD7657/AD7658. There are eight AVCC supply pins
on the parts. The AVCC supply is the supply that is used for the
AD7656/AD7657/AD7658 conversion process; therefore, it
should be well decoupled. Each AVCC supply pin should be
individually decoupled with a 10 µF tantalum capacitor and a
100 nF ceramic capacitor. The AD7656/AD7657/AD7658 can
operate with the internal reference or an externally applied
reference. In this configuration, the parts are configured to
operate with the external reference. The REFIN/REFOUT pin
is decoupled with a 10 µF and 100 nF capacitor pair. The three
internal reference buffers are enabled. Each of the REFCAP
pins are decoupled with the 10 µF and 100 nF capacitor pair.
Six of the AVCC supply pins are used as the supply to the six
ADC cores on the AD7656/AD7657/AD7658 and, as a result,
are used for the conversion process. Each analog input pin is
surrounded by an AVCC supply pin and an AGND pin. These
AVCC and AGND pins are the supply and ground for the indi-
vidual ADC cores. For example, Pin 33 is V1, Pin 34 is the AVCC
supply for ADC Core 1, and Pin 32 is the AGND for ADC Core
1. An alternative reduced decoupling solution is to group these
six AVCC supply pins into three pairs, Pin 34 and Pin 35, Pin 40
and Pin 41, and Pin 46 and Pin 47.
For the AD7656, a 100 µF decoupling capacitor can be placed
on each of the pin pairs. All of the other supply and reference
pins should be decoupled with a 10 µF decoupling capacitor.
When the AD7657 is configured in this reduced decoupling
configuration, each of the three AVCC pin pairs should be
decoupled with a 33 µF capacitor. When the AD7658 is con-
figured in this same configuration, each of the three AVCC
pin pairs should be decoupled with a 22 µF capacitor.
If the same supply is being used for the AVCC supply and DVCC
supply, a ferrite or small RC filter should be placed between the
supply pins.
The AGND pins are connected to the AGND plane of the system.
The DGND pins are connected to the digital ground plane in
the system. The AGND and DGND planes should be connected
together at one place in the system. This connection should be
made as close as possible to the AD7656/AD7657/AD7658 in
the system.
Table 9. LSB Size for Each Analog Input Range
Range AD7656 AD7657 AD7658
Input Range ±10 V ±5 V ±10 V ±5 V ±10 V ±5 V
LSB Size 0.305 mV 0.152 mV 1.22 mV 0.610 mV 4.88 mV 2.44mV
FS Range
20 V/65536
10 V/65536
20 V/16384
10 V/16384
20 V/4096
10 V/4096
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 22 of 32
+100nF
100nF
++
DV
CC
100nF +
100nF
DV
CC
AV
CC
AGND DGND V
DRIVE
DGND
V
DD
AGND
+100nF V
SS
AGND
+100nF
+100nF
REF CAP A, B, C
AGND
REFIN/OUT
AGND
D0 TO D15
CONV S T A, B, C
CS
RD
BUSY
SER/PAR
H/S
W/B
RANGE
RESET
STBY V
DRIVE
AD7656/AD7657/AD7658
10µF
µP/µC/DSP
10µF
10µF
10µF
10µF
10µF
10µF
DIGITAL SUPPLY
VOLTAGE +3V OR +5V
ANALOG SUPPLY
VOLTAGE 5V
1
1
DECO UP LING SHOWN ON T HE AV
CC
PI N AP P LIE S TO E ACH AV
CC
PI N.
2
SEE POWER SUPPLY CONFIGURATION SECTION.
+9.5V TO + 16.5V
2
SUPPLY
2.5V
REF
SI X ANALOG
INPUTS
–9.5V TO –16.5V
2
SUPPLY
PARALLEL
INTERFACE
05020-006
Figure 26. Typical Connection Diagram
The VDRIVE supply is connected to the same supply as the
processor. The voltage on VDRIVE controls the voltage value
of the output logic signals.
The VDD and VSS signals should be decoupled with a minimum
10 µF decoupling capacitor. These supplies are used for the high
voltage analog input structures on the AD7656/AD7657/AD7658
analog inputs.
DRIVING THE ANALOG INPUTS
Together, the driver amplifier and the analog input circuit used
for the AD7656 must settle for a full-scale step input to a 16-bit
level (0.0015%), which is within the specified 550 ns acquisition
time of the AD7656. The noise generated by the driver amplifier
needs to be kept as low as possible to preserve the SNR and
transition noise performance of the AD7656.
The driver also needs to have a THD performance suitable to
that of the AD7656. The AD8021 meets all these requirements.
The AD8021 needs an external compensation capacitor of
10 pF. If a dual version of the AD8021 is required, the AD8022
can be used. The AD8610 and the AD797 can also be used to
drive the AD7656/AD7657/AD7658.
INTERFACE SECTION
The AD7656/AD7657/AD7658 provide two interface options, a
parallel interface and a high speed serial interface. The required
interface mode is selected via the SER/PAR pin. The parallel
interface can operate in word (W/B = 0) or byte (W/B = 1) mode.
The interface modes are discussed in the following sections.
Parallel Interface (SER/PAR = 0)
The AD7656/AD7657/AD7658 consist of six 16-/14-/12-bit
ADCs, respectively. A simultaneous sample of all six ADCs can
be performed by connecting all three CONVST pins together,
CONVST A, CONVST B, and CONVST C. The AD7656/AD7657/
AD7658 need to see a CONVST pulse to initiate a conversion;
this should consist of a falling CONVST edge followed by a
rising CONVST edge. The rising edge of CONVSTx initiates
simultaneous conversions on the selected ADCs. The AD7656/
AD7657/AD7658 contain an on-chip oscillator that is used to
perform the conversions. The conversion time, tCONV, is 3 µs.
The BUSY signal goes low to indicate the end of conversion.
The falling edge of the BUSY signal is used to place the track-
and-hold into track mode. The AD7656/AD7657/AD7658 also
allow the six ADCs to be converted simultaneously in pairs by
pulsing the three CONVST pins independently. CONVST A is
used to initiate simultaneous conversions on V1 and V2,
CONVST B is used to initiate simultaneous conversions on
V3 and V4, and CONVST C is used to initiate simultaneous
conversions on V5 and V6. The conversion results from the
simultaneously sampled ADCs are stored in the output data
registers.
Data can be read from the AD7656/AD7657/AD7658 via the
parallel data bus with standard CS and RD signals (W/B = 0).
To read the data over the parallel bus, SER/PAR should be tied
low. The CS and RD input signals are internally gated to enable
the conversion result onto the data bus. The data lines DB0 to
DB15 leave their high impedance state when both CS and RD
are logic low.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 23 of 32
The CS signal can be permanently tied low, and the RD signal
can be used to access the conversion results. A read operation
can take place after the BUSY signal goes low. The number of
required read operations depends on the number of ADCs that
are simultaneously sampled (see Figure 27). If CONVST A
and CONVST B are simultaneously brought low, four read
operations are required to obtain the conversion results from
V1, V2, V3, and V4. If CONVST A and CONVST C are
simultaneously brought low, four read operations are required
to obtain the conversion results from V1, V2, V5, and V6.
The conversion results are output in ascending order. For
the AD7657, DB15 and DB14 contain two leading zeros and
DB[13:0] output the 14-bit conversion result. For the AD7658,
DB[15:12] contain four leading zeros, and DB[11:0] output the
12-bit conversion result.
When using the three CONVST signals to independently
initiate conversions on the three ADC pairs, care should be
taken to ensure that a conversion is not initiated on a channel
pair when the BUSY signal is high. It is also recommended not
to initiate a conversion during a read sequence because doing so
can affect the performance of the conversion. For the specified
performance, it is recommended to perform the read after the
conversion. For unused input channel pairs, the associated
CONVSTx pin should be tied to VDRIVE.
If there is only an 8-bit bus available, the AD7656/AD7657/
AD7658 interface can be configured to operate in byte mode
(W/B = 1). In this configuration, the DB7/HBEN/DCEN pin
takes on its HBEN function. Each channel conversion result
from the AD7656/AD7657/AD7658 can be accessed in two
read operations, with 8 bits of data provided on DB15 to DB8
for each of the read operations (see Figure 28). The HBEN pin
determines whether the read operation first accesses the high
byte or the low byte of the 16-bit conversion result. To always
access the low byte first on DB15 to DB8, the HBEN pin should
be tied low. To always access the high byte first on DB15 to
DB8, the HBEN pin should be tied high. In byte mode when all
three CONVST pins are pulsed together to initiate simultaneous
conversions on all six ADCs, 12 read operations are necessary
to read back the six 16-/14-/12-bit conversion results. DB[6:0]
should be left unconnected in byte mode.
V1 V2 V3 V4 V5 V6
CONV S T A,
CONV S T B,
CONV S T C
BUSY
CS
RD
DB0 TO DB15
tQUIET
t7t8
t9
t4
t2
t3t5
t6
tACQ
tCONVERT
05020-007
t
10
Figure 27. Parallel Interface Timing Diagram (W/B = 0)
LOW BYTE HIG H BY TE
DB15 TO DB8
CS
RD
t
3
t
6
t
7
t
8
t
4
t
5
t
9
05020-008
Figure 28. Parallel Interface—Read Cycle for Byte Mode of Operation (W/B = 1, HBEN = 0)
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 24 of 32
Software Selection of ADCs
The H/S SEL pin determines the source of the combination of
ADCs that are to be simultaneously sampled. When the H/S SEL
pin is logic low, the combination of channels to be simultaneously
sampled is determined by the CONVST A, CONVST B, and
CONVST C pins. When the H/S SEL pin is logic high, the
combination of channels selected for simultaneous sampling is
determined by the contents of the Control Register DB15 to
Control Register DB13. In this mode, a write to the control
register is necessary.
The control register is an 8-bit write-only register. Data is written
to this register using the CS and WR pins and the DB[15:8] data
pins (see Figure 29). The control register is shown in Table 10.
To select an ADC pair to be simultaneously sampled, set the
corresponding data line high during the write operation.
The AD7656/AD7657/AD7658 control register allows
individual ranges to be programmed on each ADC pair.
DB12 to DB10 in the control register are used to program
the range on each ADC pair.
After a reset occurs on the AD7656/AD7657/AD7658, the
control register contains all zeros.
The CONVST A signal is used to initiate a simultaneous
conversion on the combination of channels selected via the
control register. The CONVST B and CONVST C signals can
be tied low when operating in software mode (H/S SEL = 1).
The number of read pulses required depends on the number
of ADCs selected in the control register and on whether the
devices are operating in word or byte mode. The conversion
results are output in ascending order.
During the write operation, Data Bus Bit DB15 to Bit DB8 are
bidirectional and become inputs to the control register when
RD is logic high and CS and WR are logic low. The logic state
on DB15 through DB8 is latched into the control register when
WR goes logic high.
Table 10. Control Register Bit Function Descriptions
(Default All 0s)
DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8
VC VB VA RNGC RNGB RNGA REFEN REFBUF
Table 11.
Bit Mnemonic Comment
DB15 VC This bit is used to select Analog Inputs V5
and V6 for the next conversion.
When this bit = 1, V5 and V6 are
simultaneously converted on the
next CONVST A rising edge.
DB14 VB This bit is used to select Analog Inputs
V3 and V4 for the next conversion.
When this bit = 1, V3 and V4 are
simultaneously converted on the
next CONVST A rising edge.
DB13 VA This bit is used to select Analog Inputs
V1 and V2 for the next conversion.
When this bit = 1, V1 and V2 are
simultaneously converted on the
next CONVST A rising edge.
DB12 RNGC This bit is used to select the analog input
range for Analog Inputs V5 and V6.
When this bit = 1, the ±2 × VREF mode is
selected for the next conversion.
When this bit = 0, the ±4 × VREF mode is
selected for the next conversion.
DB11 RNGB This bit is used to select the analog input
range for Analog Inputs V3 and V4.
When this bit = 1, the ±2 × VREF mode is
selected for the next conversion.
When this bit = 0, the ±4 × VREF mode is
selected for the next conversion.
DB10 RNGA This bit is used to select the analog input
range for Analog Inputs V1 and V2.
When this bit = 1, the ±2 × VREF mode is
selected for the next conversion.
When this bit = 0, the ±4 × VREF mode is
selected for the next conversion.
DB9 REFEN This bit is used to select the internal
reference or an external reference.
When this bit = 0, the external reference
mode is selected. When this bit = 1, the
internal reference is selected.
DB8 REFBUF This bit is used to select between using the
internal reference buffers and choosing
to bypass these reference buffers.
When this bit = 0, the internal reference
buffers are enabled and decoupling is
required on the REFCAP pins. When this
bit = 1, the internal reference buffers are
disabled and a buffered reference should
be applied to the REFCAP pins.
DATA
DB15 TO DB8
CS
t13
t15
t14
t11
t12
WR
05020-009
Figure 29. Parallel Interface—Write Cycle for Word Mode (W/B= 0)
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 25 of 32
Changing the Analog Input Range (H/S SEL = 0)
The AD7656/AD7657/AD7658 RANGE pin allows the user to
select either ±2 × VREF or ±4 × VREF as the analog input range for
the six analog inputs. When the H/S SEL pin is low, the logic
state of the RANGE pin is sampled on the falling edge of the
BUSY signal to determine the range for the next simultaneous
conversion. When the RANGE pin is logic high at the falling
edge of the BUSY signal, the range for the next conversion is
±2 × VREF. When the RANGE pin is logic low at the falling
edge of the BUSY signal, the range for the next conversion is
±4 × VREF. After a RESET pulse, the range is updated on the first
falling BUSY edge after the RESET pulse.
Changing the Analog Input Range (H/S SEL = 1)
When the H/S SEL pin is high, the range can be changed by
writing to the control register. DB[12:10] in the control register
are used to select the analog input ranges for the next conversion.
Each analog input pair has an associated range bit, allowing
independent ranges to be programmed on each ADC pair.
When the RNGx bit = 1, the range for the next conversion
is ±2 × VREF. When the RNGx bit = 0, the range for the next
conversion is ±4 × VREF.
Serial Interface (SER/PAR = 1)
By pulsing one, two, or all three CONVST x signals, the
AD7656/AD7657/AD7658 use their on-chip trimmed oscillator
to simultaneously convert the selected channel pairs on the
rising edge of CONVST x. After the rising edge of CONVST x,
the BUSY signal goes high to indicate that the conversion has
started. It returns low when the conversion is complete 3 µs
later. The output register is loaded with the new conversion
results, and data can be read from the AD7656/AD7657/AD7658.
To read the data back from the parts over the serial interface,
SER/PAR should be tied high. The CS and SCLK signals are
used to transfer data from the AD7656/AD7657/AD7658. The
parts have three DOUT pins, DOUT A, DOUT B, and DOUT C.
Data can be read back from each part using one, two, or all
three DOUT lines.
Figure 30 shows six simultaneous conversions and the read
sequence using three DOUT lines. Also in Figure 30, 32 SCLK
transfers are used to access data from the AD7656/AD7657/
AD7658; however, two 16 SCLK individually framed transfers
with the CS signal can also be used to access the data on the
three DOUT lines. When operating the AD7656/AD7657/AD7658
in serial mode with conversion data clocking out on all three
DOUT lines, DB0/SEL A, DB1/SEL B, and DB2/SEL C should be
tied to VDRIVE. These pins are used to enable the DOUT A to
DOUT C lines, respectively.
If it is required to clock conversion data out on two data out
lines, DOUT A and DOUT B should be used. To enable DOUT A
and DOUT B, DB0/SEL A and DB1/SEL B should be tied to
VDRIVE and DB2/SEL C should be tied low. When six simultaneous
conversions are performed and only two DOUT lines are used,
a 48 SCLK transfer can be used to access the data from the
AD7656/AD7657/AD7658. The read sequence is shown in
Figure 31 for a simultaneous conversion on all six ADCs using
two DOUT lines. If a simultaneous conversion occurred on all
six ADCs, and only two DOUT lines are used to read the results
from the AD7656/AD7657/AD7658. DOUT A clocks out the
result from V1, V2, and V5, while DOUT B clocks out the
results from V3, V4, and V6.
Data can also be clocked out using just one DOUT line, in
which case, DOUT A should be used to access the conversion
data. To configure the AD7656/AD7657/AD7658 to operate in
this mode, DB0/SEL A should be tied to VDRIVE and DB1/SEL B
and DB2/SEL C should be tied low. The disadvantage of using
just one DOUT line is that the throughput rate is reduced. Data
can be accessed from the AD7656/AD7657/AD7658 using one
96 SCLK transfer, three 32 SCLK individually framed transfers,
or six 16 SCLK individually framed transfers. In serial mode,
the RD signal should be tied low. The unused DOUT line(s)
should be left unconnected in serial mode.
Serial Read Operation
Figure 32 shows the timing diagram for reading data from the
AD7656/AD7657/AD7658 in serial mode. The SCLK input signal
provides the clock source for the serial interface. The CS signal
goes low to access data from the AD7656/AD7657/AD7658.
The falling edge of CS takes the bus out of three-state and
clocks out the MSB of the 16-bit conversion result. The ADCs
output 16 bits for each conversion result; the data stream of the
AD7656 consists of 16 bits of conversion data provided MSB
first. The data stream for the AD7657 consists of two leading
zeros followed by 14 bits of conversion data MSB first. The data
stream for the AD7658 consists of four leading zeros and 12 bits
of conversion data provided MSB first.
The first bit of the conversion result is valid on the first SCLK
falling edge after the CS falling edge. The subsequent 15 data
bits are clocked out on the rising edge of the SCLK signal. Data
is valid on the SCLK falling edge. To access each conversion
result, 16 clock pulses must be provided to the AD7656/AD7657/
AD7658. Figure 32 shows how a 16 SCLK read is used to access
the conversion results.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 26 of 32
V1 V2
CONV S T A,
CONV S T B,
CONV S T C
BUSY
CS
DOUT A
DOUT B
DOUT C
32
V3 V4
V5 V6
SCLK
16
tQUIET
tACQ
tCONVERT
05020-010
Figure 30. Serial Interface with Three DOUT Lines
V1 V2 V5
DOUT A
DOUT B
48
V3 V4 V6
SCLK
CS
05020-011
Figure 31. Serial Interface with Two DOUT Lines
BUSY
ACQUISITION CONVERSION ACQUISITION
SCLK
CS
DOUT A,
DOUT B,
DOUT C
DB15 DB14 DB13 DB1 DB0
t
ACQ
t
10
t
CONVERT
t
2
t
1
t
QUIET
t
21
t
20
t
17
t
16
t
18
t
19
05020-012
CONV S T A,
CONV S T B,
CONV S T C
Figure 32. Serial Read Operation
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 27 of 32
Daisy-Chain Mode (DCEN = 1, SER/PAR = 1)
When reading conversion data back from the AD7656/AD7657/
AD7658 using their three/two/one DOUT pins, it is possible
to configure the parts to operate in daisy-chain mode, using
the DCEN pin. This daisy-chain feature allows multiple AD7656/
AD7657/AD7658 devices to be cascaded together and is useful
for reducing component count and wiring connections. An
example connection of two devices is shown in Figure 33. This
configuration shows two DOUT lines being used. Simultaneous
sampling of the 12 analog inputs is possible by using a common
CONVSTx signal. The DB5, DB4, and DB3 data pins are used
as data input pins DCIN [A:C] for the daisy-chain mode.
The rising edge of CONVST is used to initiate a conversion on
the AD7656/AD7657/AD7658. After the BUSY signal has gone
low to indicate that the conversion is complete, the user can
begin to read the data from the two devices. Figure 34 shows the
serial timing diagram when operating two AD7656/AD7657/
D7658 devices in daisy-chain mode.
The CS falling edge is used to frame the serial transfer from the
AD7656/AD7657/AD7658 devices, to take the bus out of three-
state, and to clock out the MSB of the first conversion result. In
the example shown in Figure 34, all 12 ADC channels are
simultaneously sampled. Two DOUT lines are used to read the
conversion results in this example. CS frames a 96 SCLK transfer.
During the first 48 SCLKs, the conversion data is transferred
from Device 2 to Device 1. DOUT A on Device 2 transfers
conversion data from V1, V2, and V5 into DCIN A in Device 1.
DOUT B on Device 2 transfers conversion results from V3, V4,
and V6 to DCIN B in Device 1. During the first 48 SCLKs,
Device 1 transfers data into the digital host. DOUT A on
Device 1 transfers conversion data from V1, V2, and V5.
DOUT B on Device 1 transfers conversion data from V3, V4,
and V6. During the last 48 SCLKs, Device 2 clocks out zeros
and Device 1 shifts the data clocked in from Device 2 during
the first 48 SCLKs into the digital host. This example can
also be implemented using six 16 SCLK individually framed
transfers if DCEN remains high during the transfers.
Figure 35 shows the timing if two AD7656/AD7657/AD7658
devices are configured in daisy-chain mode and are operating
with three DOUT lines. Assuming a simultaneous sampling of
all 12 inputs occurs, the CS frames a 64 SCLK transfer during
the read operation. During the first 32 SCLKs of this transfer,
the conversion results from Device 1 are clocked into the digital
host and the conversion results from Device 2 are clocked into
Device 1. During the last 32 SCLKs of the transfer, the conver-
sion results from Device 2 are clocked out of Device 1 and into
the digital host. Device 2 clocks out zeros.
Standby/Partial Power-Down Modes of Operation
Each ADC pair can be individually placed into partial power-
down mode by bringing the CONVST x signal low before the
falling edge of BUSY. To power the ADC pair back up, the
CONVST x signal should be brought high to tell the ADC pair
to power up and place the track-and-hold into track mode.
After the power-up time from partial power-down has elapsed,
the CONVST x signal should receive a rising edge to initiate a
valid conversion. In partial power-down mode, the reference
buffers remain powered up. While an ADC pair is in partial power-
down mode, conversions can still occur on the other ADCs.
The AD7656/AD7657/AD7658 have a standby mode whereby
the devices can be placed into a low power consumption mode
(100 µW maximum). The AD7656/AD7657/AD7658 are placed
into standby mode by bringing the logic input STBY low and
can be powered up again for normal operation by bringing
STBY logic high. The output data buffers are still operational
when the AD7656/AD7657/AD7658 are in standby mode,
meaning the user can continue to access the conversion results
of the parts. This standby feature can be used to reduce the
average power consumed by the AD7656/AD7657/AD7658
when operating at lower throughput rates. The parts can be
placed into standby at the end of each conversion when
BUSY goes low and taken out of standby again prior to the
next conversion. The time for the AD7656/AD7657/AD7658
to come out of standby is called the wake-up time. The wake-
up time limits the maximum throughput rate at which the
AD7656/AD7657/AD7658 can operate when powering down
between conversions. See the Specifications section.
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 28 of 32
DIGITAL HOST
CONVERT
CS
SCLK
AD7656/AD7657/AD7658 AD7656/AD7657/AD7658
CONVST
CONVST
CS CS
SCLK SCLK
DATA IN1
DATA IN2
DOUT A
DOUT B
DOUT A
DOUT B
DCIN A
DCIN B
DCEN = 1
DEVICE 1
DCEN = 0
DEVICE 2
05020-013
Figure 33. Daisy-Chain Configuration
DEVICE 1, DOUT A MSB V1 LSB V1 MSB V2 LSB V2 MSB V5 LSB V5 MSB V1 LSB V1 MSB V2 LSB V5
MSB V1 LSB V1 MSB V2 L SB V2 MSB V5 LSB V5
1 2 3
BUSY
SCLK
CS
15 16 17 31 32 33 47 48 49 63 6564 94 95 96
DEVICE 1, DOUT B MSB V3 LSB V3 MSB V4 LSB V4 MSB V6 LSB V6 MSB V3 LSB V3 MSB V4 LSB V6
DEVICE 2, DOUT A
MSB V3 LSB V3 MSB V4 L SB V4 MSB V6 LSB V6
DEVICE 2, DOUT B
05020-014
CONVST A,
CONVST B,
CONVST C
Figure 34. Daisy-Chain Serial Interface Timing with Two DOUT Lines
DEVI CE 1, DOUT A MSB V1 LSB V1 MSB V2 LSB V2 MSB V1 LSB V1 MSB V2 LSB V2
MSB V1 LSB V1 MSB V2 LSB V2
1 2 3
BUSY
SCLK
CS
15 16 17 31 32 33 47 48 49 63 64
DEVI CE 2, DOUT A
MSB V3 LSB V3 MSB V4 LSB V4
DEVI CE 2, DOUT B
DEVI CE 1, DOUT B MSB V3 LSB V3 MSB V4 LSB V4 MSB V3 LSB V3 MSB V4 LSB V4
DEVI CE 1, DOUT C MSB V5 LSB V5 MSB V6 LSB V6 MSB V5 LSB V5 MSB V6 LSB V6
MSB V5 LSB V5 MSB V6 LSB V6
DEVI CE 2, DOUT C
05020-015
CONVS T A,
CONVS T B,
CONVS T C
Figure 35. Daisy-Chain Serial Interface Timing with Three DOUT Lines
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 29 of 32
APPLICATION HINTS
LAYOUT
The printed circuit board that houses the AD7656/AD7657/
AD7658 should be designed so that the analog and digital
sections are separated and confined to certain areas of the board.
At least one ground plane should be used. It could be common
or split between the digital and analog sections. In the case of
the split plane, the digital and analog ground planes should be
joined in only one place, preferably underneath the AD7656/
AD7657/AD7658, or at least as close as possible to each part.
If the AD7656/AD7657/AD7658 are in a system where multiple
devices require analog-to-digital ground connections, the con-
nection should still be made at only one point, a star ground
point, which should be established as close as possible to the
AD7656/AD7657/AD7658. Good connections should be made
to the ground plane. Avoid sharing one connection for multiple
ground pins. Individual vias or multiple vias to the ground
plane should be used for each ground pin.
Avoid running digital lines under the devices because doing so
couples noise onto the die. The analog ground plane should be
allowed to run under the AD7656/AD7657/AD7658 to avoid
noise coupling. Fast-switching signals like CONVST or clocks
should be shielded with digital ground to avoid radiating noise
to other sections of the board, and they should never run near
analog signal paths. Crossover of digital and analog signals
should be avoided. Traces on different but close layers of the
board should run at right angles to each other to reduce the
effect of feedthrough through the board.
The power supply lines to the AVCC, DVCC, VDRIVE, VDD, and VSS
pins on the AD7656/AD7657/AD7658 should use as large a
trace as possible to provide low impedance paths and reduce the
effect of glitches on the power supply lines. Good connections
should be made between the AD7656/AD7657/AD7658 supply
pins and the power tracks on the board; this should involve the
use of a single via or multiple vias for each supply pin.
Good decoupling is also important to lower the supply
impedance presented to the AD7656/AD7657/AD7658 and to
reduce the magnitude of the supply spikes. Decoupling ceramic
capacitors, typically 100 nF, should be placed on all of the power
supply pins, VDD, VSS, AVCC, DVCC, and VDRIVE. These decoupling
capacitors should be placed close to, ideally right up against,
these pins and their corresponding ground pins. Additionally,
low ESR 10 μF capacitors should be placed on each of the
supply pins. Avoid sharing these capacitors between pins. Use
big vias to connect the capacitors to the power and ground
planes. Use wide, short traces between the via and the capacitor
pad, or place the via adjacent to the capacitor pad to minimize
parasitic inductances. Recommended decoupling capacitors are
100 nF, low ESR, ceramic capacitors (Farnell 335-1816) and
10 μF, low ESR, tantalum capacitors (Farnell 197-130) for the
AVCC decoupling. A large tantalum decoupling capacitor should
be placed where the AVCC supply enters the board.
An alternative reduced decoupling arrangement is outlined in
the Typical Connection Diagram section. This decoupling
arrangement groups the AVCC supply pins into pairs and allows
the decoupling capacitors to be shared between the supply pairs.
Group the six AVCC core supply pins into three pairs, Pin 34 and
Pin 35, Pin 40 and Pin 41, and Pin 46 and Pin 47. Connect the
supply pins in each pair together; their location on the AD7656/
AD7657/AD7658 pin configuration easily facilitates this. For
the AD7656, decouple each pair with a 100 µF capacitor; for the
AD7657, decouple each pair with a 33 µF capacitor; for the
AD7658, decouple each pair with a 22 µF capacitor. For this
minimum decoupling configuration, all other supply and
reference pins should be decoupled with a 10 µF decoupling
capacitor.
POWER SUPPLY CONFIGURATION
As outlined in the Absolute Maximum Ratings section, the
analog inputs should not be applied to the AD7656/AD7657/
AD7658 until after the AD7656/AD7657/AD7658 power
supplies have been applied to the device. However, if a
condition exists where the system analog signal conditioning
circuitry supplies are different to the VDD and VSS supplies of
the AD7656/AD7657/AD7658, or if the analog inputs may be
applied prior to the AD7656/AD7657/AD7658 supplies being
established, then an analog input series resister and Schottky
diodes in series with the VDD and VSS supplies are recom-
mended, see Figure 36. This configuration should also be
used if AVCC is applied to the AD7656/AD7657/AD7658
prior to VDD and VSS.
V1 VDD
VSS
VSS
VDD
240Ω
ANALOG
INPUTS
V2
V3 AD7656/
AD7657/
AD7658
V4
V5
V6
05020-036
Figure 36. Power Supply Configuration
AD7656/AD7657/AD7658 Data Sheet
Rev. D | Page 30 of 32
OUTLINE DIMENSIONS
COMP LIANT TO JEDEC STANDARDS MS-026-BCD
051706-A
TOP VIEW
(PINS DOWN)
1
16
17 33
32
48
4964
0.27
0.22
0.17
0.50
BSC
LEAD P ITCH
12.20
12.00 SQ
11.80
PIN 1
1.60
MAX
0.75
0.60
0.45
10.20
10.00 SQ
9.80
VIEW A
0.20
0.09
1.45
1.40
1.35
0.08
COPLANARITY
VIEW A
ROTATE D 90° CCW
SEATING
PLANE
0.15
0.05
7°
3.5°
0°
Figure 37. 64-Lead Low Profile Quad Flat Package [LQFP]
(ST-64-2)
Dimensions shown in millimeters
ORDERING GUIDE
Model1, 2 Temperature Range Package Description Package Option
AD7656BSTZ −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7656BSTZ-REEL −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7656YSTZ −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7656YSTZ-REEL −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7657BSTZ −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7657BSTZ-REEL −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7657YSTZ −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7657YSTZ-REEL −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7658BSTZ −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7658BSTZ-REEL −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7658YSTZ −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
AD7658YSTZ-REEL −40°C to +125°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
EVAL-AD7656CBZ Evaluation Board
EVAL-AD7657CBZ Evaluation Board
EVAL-AD7658CBZ Evaluation Board
EVAL-CONTROL BRD2Z Controller Board
1 Z = RoHS Compliant Part.
2 The EVAL-CONTROL BRD2Z is a complete unit allowing a PC to control and communicate with all Analog Devices evaluation boards ending in the CB designators. To
order a complete evaluation kit, the particular ADC evaluation board, for example, EVAL-AD7656/AD7657/AD7658CBZ, the EVAL-CONTROL BRD2Z and a 12 V
transformer must be ordered. See the relevant evaluation board technical note for more information.
Data Sheet AD7656/AD7657/AD7658
Rev. D | Page 31 of 32
NOTES
