AD AD7173-8

Low Power, 8-/16-Channel, 31.25 kSPS,
24-Bit, Highly Integrated Sigma-Delta ADC
AD7173-8
Data Sheet
FEATURES
APPLICATIONS
Low power, 8-/16-channel, highly integrated multiplexed
analog-to-digital converter (ADC)
Integration
Precision analog input buffers and reference input buffers
2.5 V precision reference (3.5 ppm/°C)
Cross point multiplexer (enable system diagnostic)
8 full differential or 16 single-ended channels
Clock oscillator
GPIO and GPO pins with automatic external mux control
Fast and flexible output rate: 1.25 SPS to 31.25 kSPS
Channel scan data rate: 6.21 kSPS/channel (161 µs settling)
Performance specifications
17.5 noise free bits at 31.25 kSPS
24 noise free bits at 1.25 SPS
INL: ±3 ppm/FSR
85 dB rejection of 50 Hz and 60 Hz with 50 ms settling
Operates with either 3.3 V or5 V supply
Single supply
3.3 V or 5 V AVDD1, 2 V to 5 V AVDD2, and 2 V to 5 V IOVDD
Optional split supply
AVDD1 and AVSS ± 2.5 V or AVDD1 and AVSS ± 1.65 V
Current: 1.4 mA
3-/4-wire serial digital interface (Schmitt trigger on SCLK)
CRC error checking
SPI, QSPI, MICROWIRE, and DSP compatible
Package: 40-lead 6 mm × 6 mm LFCSP
Temperature range: −40°C to +105°C
Process control: PLC/DCS modules
Voltage, current, temperature, and pressure measurement
Flow meters
Medical and scientific multichannel instrumentation
Seismic instrumentation
Chemical analysis instrumentation: chromatography
GENERAL DESCRIPTION
Fast settling, highly accurate, low power, 8-/16-channel,
multiplexed ADC for low bandwidth input signals with
integrated input buffers.
Integrated precision, 2.5 V, low drift (3.5 ppm/°C), band gap
reference and integrated oscillator.
Eight flexible setups with configurability for output data rate,
digital filter mode, offset/gain error correction, reference
selection, buffer enables and more.
Sinc5 + sinc1 filter maximizes channel scan rate, and sinc3 filter
maximizes resolution and enhanced 50 Hz/60 Hz rejection,
with four selectable options to maximize rejection.
Integrated diagnostic features, including CRC, register checksum,
temperature sensor, crosspoint multiplexer, burnout currents,
and GPIOs/GPOs.
FUNCTIONAL BLOCK DIAGRAM
AVDD1
AVDD2 REGCAPA
BUFFERED
PRECISION
REFERENCE
1.8V
LDO
1.8V
LDO
REFERENCE
INPUT
BUFFERS
CROSSPOINT
MULTIPLEXER
AIN0/REF2–
IOVDD REGCAPD
REF– REF+ REFOUT
AVDD
AIN1/REF2+
INT
REF
ANALOG
INPUT
BUFFERS
CS
SCLK
DIGITAL
FILTER
Σ-Δ ADC
SERIAL
INTERFACE
AND CONTROL
DIN
DOUT/RDY
SYNC
AIN15
AVSS
AIN16
ERROR
XTAL AND INTERNAL
CLOCK OSCILLATOR
CIRCUITRY
I/O CONTROL
AD7173-8
AVSS
PDSW
GPIO0 GPIO1 GPIO2 GPIO3
XTAL1 XTAL2/CLKIO
DGND
11773-001
TEMPERATURE
SENSOR
Figure 1.
Rev. 0
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Technical Support
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AD7173-8
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Diagnostics ...................................................................................... 42
General Description ......................................................................... 1
General-Purpose I/O ................................................................. 42
Functional Block Diagram .............................................................. 1
16-Bit/24-Bit Conversions......................................................... 42
Revision History ............................................................................... 2
Serial Interface Reset (DOUT_RESET) .................................. 42
Specifications..................................................................................... 3
Synchronization .......................................................................... 42
Timing Characteristics ................................................................ 7
Error Flags ................................................................................... 43
Absolute Maximum Ratings ............................................................ 8
DATA_STAT ............................................................................... 43
Thermal Resistance ...................................................................... 8
IOSTRENGTH Bit ..................................................................... 43
ESD Caution .................................................................................. 8
Grounding and Layout .................................................................. 44
Pin Configuration and Function Descriptions ............................. 9
Register Summary .......................................................................... 45
Typical Performance Characteristics ........................................... 11
Register Details ............................................................................... 47
Noise Performance and Resolution .............................................. 17
Communications Register......................................................... 47
Getting Started ................................................................................ 18
Status Register ............................................................................. 49
Power Supplies ............................................................................ 19
ADC Mode Register ................................................................... 50
Digital Communication............................................................. 19
Interface Mode Register ............................................................ 51
Configuration Overview ........................................................... 21
Register Check ............................................................................ 52
Circuit Description ......................................................................... 26
Data Register ............................................................................... 52
Analog Input ............................................................................... 26
GPIO Configuration Register ................................................... 53
Reference Options ...................................................................... 28
ID Register................................................................................... 54
Clock Source ............................................................................... 28
Channel Register 0 ..................................................................... 54
Digital Filters ................................................................................... 30
Channel Register 1 to Channel Register 15 ............................ 56
Sinc5 + Sinc1 Filter..................................................................... 30
Setup Configuration Register 0 ................................................ 57
Sinc3 Filter ................................................................................... 31
Single Cycle Settling ................................................................... 32
Setup Configuration Register 1 to Setup Configuration
Register 7 ..................................................................................... 58
Enhanced 50 Hz and 60 Hz Rejection Filters ......................... 32
Filter Configuration Register 0................................................. 59
Operating Modes ............................................................................ 35
Filter Configuration Register 1 to Filter Configuration
Register 7 ..................................................................................... 60
Continuous Conversion Mode ................................................. 35
Continuous Read Mode ............................................................. 36
Single Conversion Mode ........................................................... 37
Standby and Power-Down Modes............................................ 38
Calibration Modes ...................................................................... 38
Digital Interface .............................................................................. 39
Checksum Protection................................................................. 39
Offset Register 0 ......................................................................... 61
Offset Register 1 to Offset Register 7....................................... 61
Gain Register 0............................................................................ 61
Gain Register 1 to Gain Register 7 ........................................... 61
Outline Dimensions ....................................................................... 62
Ordering Guide .......................................................................... 62
CRC Calculation ......................................................................... 40
REVISION HISTORY
10/13—Revision 0: Initial Version
Rev. 0 | Page 2 of 64
Data Sheet
AD7173-8
SPECIFICATIONS
AVDD1 = 3.0 V to 5.5 V, AVDD2 = 2 V to 5.5 V, IOVDD = 2 V to 5.5 V, AVSS = DGND = 0 V, REF+ = 2.5 V, REF− = AVSS,
internal master clock = 2 MHz, TA = TMIN to TMAX, unless otherwise noted.
Table 1.
Parameter
ADC SPEED AND PERFORMANCE
Output Data Rate (ODR)
No Missing Codes 1
Resolution
Noise
Noise Free Resolution
ACCURACY
Integral Nonlinearity (INL)
Offset Error 2
Offset Drift
Offset Drift vs. Time 3
Gain Error2
Gain Drift vs. Temperature1
Gain Drift vs. Time3
REJECTION
Power Supply Rejection
Common-Mode Rejection
At DC
At 50 Hz and 60 Hz1
Normal Mode Rejection1
ANALOG INPUTS
Differential Input Voltage Range
Absolute AIN Voltage Limits1
Buffers Disabled
Buffers Enabled
Analog Input Current
Buffers Enabled
Input Current
Input Current Drift
Buffers Disabled
Input Current
Input Current Drift
Crosstalk
INTERNAL REFERENCE
Output Voltage
Initial Accuracy1
Temperature Coefficient
0°C to +105°C
−40°C to +105°C
Reference Load Current, ILOAD
Test Conditions/Comments
Excluding sinc3 filter at 31.25 kSPS
See Table 6
See Table 6
Sinc5 + sinc1 filter (default)
31.25 kSPS, REF+ = 5 V
2.6 kSPS, REF+ = 5 V
1.25 SPS, REF+ = 5 V
Min
Typ
1.25
24
Unit
31250
SPS
Bits
17.5
18.4
24
2.5 V reference
5 V reference
Internal short
Internal short
±3
±5
±40
±350
±450
±10
±0.5
±3
25°C, AVDD1 = 5 V
AVDD1 and AVDD2, VIN = 1 V
VIN = 0.1 V
20 SPS ODR (post filter); 50 Hz ± 1 Hz and
60 Hz ± 1 Hz
50 Hz ± 1 Hz and 60 Hz ± 1 Hz
Internal clock, 20 SPS ODR (post filter)
External clock, 20 SPS ODR (post filter)
Max
Bits
Bits
Bits
±7.5
±50
±1
90
dB
95
120
71
85
ppm/FSR
ppm/FSR
µV
nV/°C
nV/1000 hrs
ppm/FSR
ppm/FSR/°C
ppm/FSR/
1000 hrs
dB
dB
90
90
dB
dB
±VREF
V
AVSS − 0.05
AVSS
AVDD1 + 0.05
AVDD1 − 1.1
V
V
Single cycle settling enabled (default)
External clock
Internal clock (±2.5% clock)
1 kHz input
100 nF external capacitor on REFOUT to AVSS
REFOUT with respect to AVSS
TA = 25°C 4
±2
±25
nA
pA/°C
±6
±0.1
±0.5
−120
µA/V
nA/V/°C
nA/V/°C
dB
2.5
−0.1
3.5
3.5
IL
−10
Rev. 0 | Page 3 of 64
+0.1
V
% of V
8
10
+10
ppm/°C
ppm/°C
mA
AD7173-8
Parameter
Power Supply Rejection
(Line Regulation)
Load Regulation
Voltage Noise
Voltage Noise Density
Turn-On Settling Time
Long-Term Stability3
Short Circuit
EXTERNAL REFERENCE
Reference Input Voltage
Absolute Reference Input Voltage
Limits1
Buffers Disabled
Buffers Enabled
Average Reference Input Current
Buffers Disabled
Buffers Enabled
Average Reference Input Current Drift
External clock
Internal clock
Normal Mode Rejection1
Common-Mode Rejection
TEMPERATURE SENSOR
Accuracy
Sensitivity
BURNOUT CURRENTS
Source/Sink Current
BRIDGE POWER-DOWN SWITCH
RON
Allowable Currents
GENERAL-PURPOSE I/O (GPIO0, GPIO1,
GPO2, GPO3)
Input Mode Leakage Current1
Floating State Output Capacitance
AVDD1 − AVSS = 5 V
Output High Voltage, VOH1
Output Low Voltage, VOL1
Input High Voltage, VIH1
Input Low Voltage, VIL1
AVDD1 − AVSS = 3.3 V
Output High Voltage, VOH1
Output Low Voltage, VOL1
Input High Voltage, VIH1
Input Low Voltage, VIL1
CLOCK
Internal Clock
Frequency
Accuracy
Duty Cycle
Output Low Voltage, VOL
Output High Voltage, VOH
Crystal
Frequency
Start-Up Time
External Clock (CLKIO)
Duty Cycle1
Data Sheet
Test Conditions/Comments
AVDD1 and AVDD2
Min
∆VOUT/∆IL
eN, 0.1 Hz to 10 Hz
eN, 1 kHz
100 nF capacitor
1000 hours
ISC
Typ
90
Max
140
6.5
215
60
460
25
Reference input = (REF+) − (REF−)
1
2.5
AVSS − 0.05
AVSS
Unit
dB
ppm/mA
µV rms
nV/√Hz
µs
ppm
mA
AVDD1
V
AVDD1 + 0.05
AVDD1
V
V
±9
±50
µA/V
nA
±5
±6
nA/V/°C
nA/V/°C
83
dB
After user calibration at 25°C
±2
477
°C
µV/°C
Analog input buffers must be enabled
±10
µA
Buffers disabled
See the Rejection parameter
24
16
Ω
mA
With respect to AVSS
−10
+10
5
ISOURCE = 200 µA
ISINK = 800 µA
AVSS + 4
AVSS + 0.4
AVSS + 3
AVSS + 0.7
ISOURCE = 200 µA
ISINK = 800 µA
AVSS + 2.7
V
V
V
V
AVSS + 0.45
V
V
V
V
+2.5
MHz
%
AVSS + 0.27
AVSS + 2
2
−2.5
µA
pF
50:50
0.4
V
V
16.384
MHz
µs
MHz
0.8 × IOVDD
14
Typical duty cycle 50:50 (maximum:minimum)
Rev. 0 | Page 4 of 64
30:70
16
10
2
50:50
2.048
70:30
Data Sheet
Parameter
LOGIC INPUTS
Input High Voltage, VINH1
Input Low Voltage, VINL1
Hysteresis1
Leakage Currents
LOGIC OUTPUT (DOUT/RDY)
Output High Voltage, VOH1
Output Low Voltage, VOL1
Leakage Current
Output Capacitance
SYSTEM CALIBRATION1
Full-Scale Calibration Limit
Zero-Scale Calibration Limit
Input Span
POWER REQUIREMENTS
Power Supply Voltage
AVDD1 − AVSS
AVDD2 − AVSS
AVSS − DGND
IOVDD − DGND
IOVDD − AVSS
POWER SUPPLY CURRENTS
Full Operating Mode
AVDD1 Current
AVDD1 = 5 V Typical,
5.5 V Maximum
AVDD1 = 3.3 V Typical,
3.6 V Maximum1
AVDD2 Current
IOVDD Current
Standby Mode
Standby (LDO on)
Power-Down Mode
AD7173-8
Test Conditions/Comments
Min
2 V ≤ IOVDD ≤ 2.3 V
2.3 V ≤ IOVDD ≤ 5.5 V
2 V ≤ IOVDD ≤ 2.3 V
2.3 V ≤ IOVDD ≤ 5.5 V
IOVDD > 2.7 V
IOVDD < 2.7 V
0.65 × IOVDD
0.7 × IOVDD
Typ
0.08
0.04
−10
IOVDD ≥ 4.5 V, ISOURCE = 1 mA
2.7 V ≤ IOVDD < 4.5 V, ISOURCE = 500 μA
IOVDD < 2.7 V, ISOURCE = 200 μA
IOVDD ≥ 4.5 V, ISINK = 2 mA
2.7 V ≤ IOVDD < 4.5 V, ISINK = 1 mA
IOVDD < 2.7 V, ISINK = 400 μA
Floating state
Floating state
Max
Unit
0.35 × IOVDD
0.7
0.25
0.2
+10
V
V
V
V
V
V
µA
0.8 × IOVDD
0.8 × IOVDD
0.8 × IOVDD
0.4
0.4
0.4
+10
−10
10
1.05 × FS
V
V
V
V
V
V
µA
pF
2.1 × FS
V
V
V
5.5
5.5
0
5.5
6.35
V
V
V
V
V
0.23
0.27
mA
0.42
0.49
mA
2.12
2.71
mA
0.945
1.22
mA
0.16
0.19
mA
0.34
0.4
mA
1.9
2.45
mA
−1.05 × FS
0.8 × FS
3.0
2
−2.75
2
For AVSS < DGND
All outputs unloaded
AIN± and REF± buffers disabled; external
reference
AIN± and REF± buffers disabled; internal
reference
AIN± and REF± buffers enabled; external
reference
Each enabled buffered pair: AIN+, AIN− and
REF+, REF−
AIN± and REF± buffers disabled; external
reference
AIN± and REF± buffers disabled; internal
reference
AIN± and REF± buffers enabled; external
reference
Each enabled buffered pair: AIN+, AIN− and
REF+, REF−
External reference
Internal reference
External clock
Internal clock
External crystal
0.87
1.13
mA
1
1.25
0.24
0.52
0.9
1.15
1.4
0.39
0.76
mA
mA
mA
mA
mA
Reference off, total current consumption
Reference on, total current consumption
Full power-down, LDO, REF±
25
400
2
Rev. 0 | Page 5 of 64
10
µA
µA
µA
AD7173-8
Parameter
POWER DISSIPATION
Full Operating Mode
Standby Mode
Power-Down Mode
Data Sheet
Test Conditions/Comments
Unbuffered, external clock and reference;
AVDD1 = 3.3 V, AVDD2 = 2 V, IOVDD = 2 V
Unbuffered, external clock and reference;
all supplies = 5 V
Unbuffered, external clock and reference;
all supplies = 5.5 V
Fully buffered, internal clock and reference
(note that REFOUT has no load); AVDD1 = 3.3 V,
AVDD2 = 2 V, IOVDD = 2 V
Fully buffered, internal clock and reference
(note that REFOUT has no load); all supplies =
5V
Fully buffered, internal clock and reference
(note that REFOUT has no load); all supplies =
5.5 V
Reference off, all supplies = 5 V
Reference on, all supplies = 5 V
Full power-down, all supplies = 5 V
Full power-down, all supplies = 5.5 V
Min
Typ
Max
Unit
3
mW
7.35
mW
9.96
mW
10.4
mW
20.4
mW
28
mW
55
µW
mW
µW
µW
125
2
10
Specification is not production tested but is supported by characterization data at the initial product release.
Following a system or internal zero-scale calibration, the offset error is in the order of the noise for the programmed output data rate selected. A system full-scale
calibration reduces the gain error to the order of the noise for the programmed output data rate.
3
This specification is noncumulative and includes MSL preconditioning effects.
4
This specification includes MSL preconditioning effects.
1
2
Rev. 0 | Page 6 of 64
Data Sheet
AD7173-8
TIMING CHARACTERISTICS
IOVDD = 2 V to 5.5 V, DGND = 0 V, Input Logic 0 = 0 V, Input Logic 1 = IOVDD, CLOAD = 20 pF, unless otherwise noted.
Table 2.
Parameter
SCLK PULSE WIDTH
t3
t4
READ OPERATION
t1
t2 3
t5 5
t6
t7
WRITE OPERATION
t8
t9
t10
t11
Limit at TMIN, TMAX
Unit
Test Conditions/Comments 1, 2
25
25
ns min
ns min
SCLK high pulse width
SCLK low pulse width
0
15
40
0
12
25
2.5
20
0
10
ns min
ns max
ns max
ns min
ns max
ns max
ns min
ns max
ns min
ns min
CS falling edge to DOUT/RDY active time
IOVDD = 4.5 V to 5.5 V
IOVDD = 2 V to 3.6 V
SCLK active edge to data valid delay 4
IOVDD = 4.5 V to 5.5 V
IOVDD = 2 V to 3.6 V
Bus relinquish time after CS inactive edge
0
8
8
5
ns min
ns min
ns min
ns min
CS falling edge to SCLK active edge setup time4
Data valid to SCLK edge setup time
Data valid to SCLK edge hold time
CS rising edge to SCLK edge hold time
SCLK inactive edge to CS inactive edge
SCLK inactive edge to DOUT/RDY high/low
Sample tested during initial release to ensure compliance.
See Figure 2 and Figure 3.
The time required for the output to cross the VOL or VOH limits.
4
The SCLK active edge is the falling edge of SCLK.
5 RDY
returns high after a read of the data register. In single conversion mode and continuous conversion mode, the same data can be read again, if required, while RDY
is high. It is important to ensure that subsequent reads do not occur close to the next output update. If the continuous read feature is enabled, the digital word can be
read only once.
1
2
3
Timing Diagrams
CS (I)
t6
t1
t5
MSB
DOUT/RDY (O)
LSB
t7
t2
t3
11773-002
SCLK (I)
t4
I = INPUT, O = OUTPUT
Figure 2. Read Cycle Timing Diagram
CS (I)
t11
t8
SCLK (I)
t9
t10
MSB
LSB
I = INPUT, O = OUTPUT
Figure 3. Write Cycle Timing Diagram
Rev. 0 | Page 7 of 64
11773-003
DIN (I)
AD7173-8
Data Sheet
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
THERMAL RESISTANCE
Table 3.
θJA is specified for a device soldered on a JEDEC test board for
surface-mount packages. The values listed in Table 4 are based
on simulated data.
Parameter
AVDD1, AVDD2 to AVSS
AVDD1 to DGND
Rating
−0.3 V to +6.5 V
−0.3 V to +6.5 V
IOVDD to DGND
IOVDD to AVSS
−0.3 V to +6.5 V
−0.3 V to +7.5 V
AVSS to DGND
Analog Input Voltage to AVSS
Reference Input Voltage to AVSS
−3.25 V to +0.3 V
−0.3 V to AVDD1 + 0.3 V
−0.3 V to AVDD1 + 0.3 V
Digital Input Voltage to DGND
Digital Output Voltage to DGND
AIN[16:0] or Digital Input Current
Operating Temperature Range
−0.3 V to IOVDD + 0.3 V
−0.3 V to IOVDD + 0.3 V
10 mA
−40°C to +105°C
Storage Temperature Range
Maximum Junction Temperature
Lead Soldering, Reflow Temperature
ESD Rating (HBM)
−65°C to +150°C
150°C
260°C
4 kV
Table 4. Thermal Resistance
Package Type
40-Lead, 6 mm × 6 mm LFCSP
1-Layer JEDEC Board
4-Layer JEDEC Board
4-Layer JEDEC Board with 16 Thermal Vias
ESD CAUTION
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.
Rev. 0 | Page 8 of 64
θJA
Unit
114
54
34
°C/W
°C/W
°C/W
Data Sheet
AD7173-8
40
39
38
37
36
35
34
33
32
31
REF+
REF–
GPO3
AIN15
AIN14
AIN13
AIN12
AIN11
AIN10
AIN9
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1
2
3
4
5
6
7
8
9
10
AD7173-8
TOP VIEW
(Not to Scale)
30
29
28
27
26
25
24
23
22
21
AIN8
AIN7
AIN6
AIN5
AIN4
GPO2
GPIO1
GPIO0
REGCAPD
DGND
NOTES
1. THE EXPOSED PAD SHOULD BE SOLDERED TO A SIMILAR PAD ON THE PCB
UNDER THE EXPOSED PAD TO CONFER MECHANICAL STRENGTH AND FOR
HEAT DISSIPATION. THE EXPOSED PAD MUST BE CONNECTED TO AVSS
THROUGH THIS PAD ON THE PCB.
11773-004
PDSW
XTAL1
XTAL2/CLKIO
DOUT/RDY
DIN
SCLK
CS
ERROR
SYNC
IOVDD
11
12
13
14
15
16
17
18
19
20
AIN16
AIN0/REF2–
AIN1/REF2+
AIN2
AIN3
REFOUT
REGCAPA
AVSS
AVDD1
AVDD2
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin
No.
1
2
Mnemonic
AIN16
AIN0/REF2−
Type 1
AI
AI
3
AIN1/REF2+
AI
4
5
6
7
8
9
10
11
12
13
AIN2
AIN3
REFOUT
REGCAPA
AVSS
AVDD1
AVDD2
PDSW
XTAL1
XTAL2/CLKIO
AI
AI
AO
AO
P
P
P
AO
AI
AI/DI
14
DOUT/RDY
DO
Description
Analog Input 16. Selectable through cross point mux.
Analog Input 0 (AIN0)/Reference 2, Negative Input (REF2−). An external reference can be applied between
REF2+ and REF2−. REF2− can span from AVSS to AVDD1 − 1 V. Analog Input 0 is selectable through cross
point mux. Reference 2 can be selected through the REFSEL bits in the setup configuration register.
Analog Input 1 (AIN0)/Reference 2, Positive Input (REF2+). An external reference can be applied between
REF2+ and REF2−. REF2+ can span from AVDD1 to AVSS + 1 V. Analog Input 1 is selectable through cross
point mux. Reference 2 can be selected through the REFSEL bits in the setup configuration register.
Analog Input 2. Selectable through cross point mux.
Analog Input 3. Selectable through cross point mux.
Buffered Output of Internal Reference. The output is 2.5 V with respect to AVSS.
Analog LDO Regulator Output. Decouple this pin to AVSS using a 1 µF capacitor.
Negative Analog Supply. This supply ranges from 0 V to −2.75 V and is nominally set to 0 V.
Analog Supply Voltage 1. This voltage ranges from 3.0 V minimum to 5.5 V maximum with respect to AVSS.
Analog Supply Voltage 2. This voltage ranges from 2 V to AVDD1 with respect to AVSS.
Power-Down Switch Connected to AVSS. This pin is controlled by the PDSW bit in the GPIOCON register.
Input 1 for Crystal.
Input 2 for Crystal (XTAL2)/Clock Input or Output (CLKIO). See the CLOCKSEL bit settings in the ADCMODE
register (Table 25) for more information.
Serial Data Output (DOUT)/Data Ready Output (RDY). This pin serves a dual purpose. It functions as a serial
data output pin to access the output shift register of the ADC. The output shift register can contain data
from any of the on-chip data or control registers. The data-word/control word information is placed on the
DOUT/RDY pin on the SCLK falling edge and is valid on the SCLK rising edge. When CS is high, the DOUT/RDY
output is tristated. When CS is low, and a register is not being read, DOUT/RDY operates as a data ready
pin, going low to indicate the completion of a conversion. If the data is not read after the conversion, the
pin goes high before the next update occurs. The DOUT/RDY falling edge can be used as an interrupt to
a processor, indicating that valid data is available.
Rev. 0 | Page 9 of 64
AD7173-8
Data Sheet
Pin
No.
15
Mnemonic
DIN
Type 1
DI
16
SCLK
DI
17
CS
DI
18
ERROR
DI/O
19
SYNC
DI
20
IOVDD
P
21
22
DGND
REGCAPD
P
AO
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
GPIO0
GPIO1
GPO2
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
GPO3
REF−
DI/O
DI/O
DO
AI
AI
AI
AI
AI
AI
AI
AI
AI
AI
AI
AI
DO
AI
40
REF+
AI
EP
P
1
Description
Serial Data Input to the Input Shift Register on the ADC. Data in this shift register is transferred to the
control registers in the ADC, with the register address (RA) bits of the communications register identifying
the appropriate register. Data is clocked in on the rising edge of SCLK.
Serial Clock Input. This serial clock input is for data transfers to and from the ADC. SCLK has a Schmitt
trigger input, making the interface suitable for opto-isolated applications.
Chip Select Input. This is an active low logic input used to select the ADC. CS can be used to select the ADC
in systems with more than one device on the serial bus. CS can be hardwired low, allowing the ADC to operate
in 3-wire mode with SCLK, DIN, and DOUT used to interface with the device. When CS is high, the
DOUT/RDY output is tristated.
This pin can be used in one of the following three modes:
Active low error input mode. This mode sets the ADC_ERROR bit in the STATUS register.
Active low, open-drain error output mode. The STATUS register error bits are mapped to the ERROR pin.
The ERROR pins of multiple devices can be wired together to a common pull-up resistor so that an error on
any device can be observed.
General-purpose output mode. The status of the pin is controlled by the ERR_DAT bit in the GPIOCON register.
The pin is referenced between IOVDD and DGND, as opposed to the AVDD1 and AVSS levels used by the
GPIO1 and GPIO2 pins. The ERROR pin has an active pull-up in this case.
Synchronization Input. Allows synchronization of the digital filters and analog modulators when using
multiple AD7173-8 devices.
Digital I/O Supply Voltage. IOVDD voltage ranges from 2 V to 5 V. IOVDD is independent of AVDD1 and
AVDD2. For example, IOVDD can be operated at 3.3 V when AVDD1 or AVDD2 equals 5 V, or vice versa. If
AVSS is set to −2.5 V, the voltage on IOVDD must not exceed 3.6 V.
Digital Ground.
Digital LDO Regulator Output. This pin is for decoupling purposes only. Decouple this pin to DGND using
a 1 µF capacitor.
General-Purpose Input/Output. Logic input/output on this this pin is referred to the AVDD1 and AVSS supplies.
General-Purpose Input/Output. Logic input/output on this this pin is referred to the AVDD1 and AVSS supplies.
General-Purpose Output. Logic output on this this pin is referred to the AVDD1 and AVSS supplies.
Analog Input 4. Selectable through cross point mux.
Analog Input 5. Selectable through cross point mux.
Analog Input 6. Selectable through cross point mux.
Analog Input 7. Selectable through cross point mux.
Analog Input 8. Selectable through cross point mux.
Analog Input 9. Selectable through cross point mux.
Analog Input 10. Selectable through cross point mux.
Analog Input 11. Selectable through cross point mux.
Analog Input 12. Selectable through cross point mux.
Analog Input 13. Selectable through cross point mux.
Analog Input 14. Selectable through cross point mux.
Analog Input 15. Selectable through cross point mux.
General-Purpose Output. Logic output on this this pin is referred to the AVDD1 and AVSS supplies.
Reference 1 Input Negative Terminal. REF− can span from AVSS to AVDD1 − 1 V. Reference 1 can be
selected through the REFSEL bits in the SETUP CONFIGURATION register.
Reference 1 Input Positive Terminal. An external reference can be applied between REF+ and REF−. REF+
can span from AVDD1 to AVSS + 1 V. Reference 1 can be selected through the REFSEL bits in the SETUP
CONFIGURATION register.
Exposed Pad. The exposed pad should be soldered to a similar pad on the PCB under the exposed paddle
to confer mechanical strength to the package and for heat dissipation. The exposed pad must be connected
to AVSS through this pad on the PCB.
AI = analog input, AO = analog output, DI/O = bidirectional digital input/output, DO = digital output, DI = digital input, P = power supply.
Rev. 0 | Page 10 of 64
Data Sheet
AD7173-8
TYPICAL PERFORMANCE CHARACTERISTICS
AVDD1 = 5 V, AVDD2 = 5 V, IOVDD = 3.3 V, unless otherwise noted.
8388539
700
600
500
ADC CODE
OCCURRENCE
8388538
400
300
8388537
200
0
100
200
300
400
500
600
700
800
900
1000
SAMPLE
0
11773-005
8388536
8388536
8388537
8388538
ADC CODE
8388539
11773-008
100
Figure 8. Noise Distribution Histogram
(Output Data Rate = 1.25 SPS, Analog Input Buffers Disabled))
Figure 5. Noise
(Output Data Rate = 1.25 SPS, Analog Input Buffers Disabled)
600
8388551
500
ADC CODE
OCCURRENCE
8388550
400
300
200
8388549
0
100
200
300
400
500
600
700
800
900
1000
SAMPLE
0
11773-006
8388548
8388548
8388549
8388550
8388551
ADC CODE
Figure 6. Noise
(Output Data Rate = 1.25 SPS, Analog Input Buffers Enabled)
11773-009
100
Figure 9. Noise Distribution Histogram
(Output Data Rate = 1.25 SPS, Analog Input Buffers Enabled)
60
8388580
8388570
50
8388560
OCCURRENCE
40
8388540
8388530
8388520
30
20
8388510
10
8388500
100
200
300
400
500
600
700
800
900
1000
SAMPLE
0
ADC CODE
Figure 7. Noise
(Output Data Rate = 10 kSPS, Analog Input Buffers Disabled)
Figure 10. Noise Distribution Histogram
(Output Data Rate = 10 kSPS, Analog Input Buffers Disabled))
Rev. 0 | Page 11 of 64
11773-010
0
8388499
8388502
8388505
8388508
8388511
8388514
8388517
8388520
8388523
8388526
8388529
8388532
8388535
8388538
8388541
8388544
8388547
8388550
8388553
8388556
8388559
8388562
8388565
8388568
8388571
8388574
8388490
11773-007
ADC CODE
8388550
AD7173-8
Data Sheet
8388610
50
8388600
45
8388590
40
8388580
35
OCCURRENCE
ADC CODE
8388570
8388560
8388550
8388540
30
25
20
15
8388530
10
8388520
5
8388510
300
400
500
600
700
800
900
1000
SAMPLE NUMBER
0
ADC CODE
Figure 14. Noise Distribution Histogram
(Output Data Rate = 10 kSPS, Analog Input Buffers Enabled))
8388580
45
8388570
40
8388560
35
8388550
30
OCCURRENCE
8388540
8388530
8388520
25
20
15
8388510
10
8388500
5
100
200
300
400
500
600
700
800
900
1000
SAMPLE NUMBER
0
11773-012
8388490
8388497
8388500
8388503
8388506
8388509
8388512
8388515
8388518
8388521
8388524
8388527
8388530
8388533
8388536
8388539
8388542
8388545
8388548
8388551
8388554
8388557
8388560
8388563
8388566
8388569
8388572
8388575
ADC CODE
Figure 11. Noise
(Output Data Rate = 10 kSPS, Analog Input Buffers Enabled)
0
11773-014
200
ADC CODE
11773-015
100
8388506
8388510
8388514
8388518
8388522
8388526
8388530
8388534
8388538
8388542
8388546
8388550
8388554
8388558
8388562
8388566
8388570
8388574
8388578
8388582
8388586
8388590
8388594
8388598
0
11773-011
8388500
Figure 15. Noise Distribution Histogram
(Output Data Rate = 31.25 kSPS, Analog Input Buffers Disabled)
Figure 12. Noise
(Output Data Rate = 31.25 kSPS, Analog Input Buffers Disabled)
40
8388620
35
8388600
30
OCCURRENCE
8388560
8388540
8388520
25
20
15
10
8388500
5
100
200
300
400
500
600
700
800
900
1000
SAMPLE NUMBER
0
ADC CODE
Figure 13. Noise
(Output Data Rate = 31.25 kSPS, Analog Input Buffers Enabled)
Figure 16. Noise Distribution Histogram
(Output Data Rate = 31.25 kSPS, Analog Input Buffers Enabled)
Rev. 0 | Page 12 of 64
11773-016
0
8388494
8388499
8388504
8388509
8388514
8388519
8388524
8388529
8388534
8388539
8388544
8388549
8388554
8388559
8388564
8388569
8388574
8388579
8388584
8388589
8388594
8388599
8388604
8388609
8388480
11773-013
ADC CODE
8388580
Data Sheet
AD7173-8
0
14
–20
12
–40
AMPLITUDE (dB)
–60
8
6
BUFFER ON, DEVICE 1
BUFFER OFF, DEVICE 1
BUFFER ON, DEVICE 2
BUFFER OFF, DEVICE 2
BUFFER ON, DEVICE 3
BUFFER OFF, DEVICE 3
–160
–180
2
3
4
5
VCM (V)
–200
0
0
18
–20
16
–40
14
–60
AMPLITUDE (dB)
RMS NOISE (µV)
20
12
10
8
4.5
5.0
–120
4
–160
2
–180
–200
11773-018
0
15
FREQUENCY (MHz)
0
2
4
6
8
10
12
14
FREQUENCY (kHz)
Figure 21. ADC Output FFT; 1 kHz Input Tone, −0.5 dBFS Input FFT
(Output Data Rate = 31.25 kSPS, External Reference,
External Clock, Buffers Enabled)
Figure 18. RMS Noise vs. Master Clock Frequency
(Output Data Rate = 31.25 kSPS, Analog Input Buffers Enabled)
0
–20
–20
–40
–40
–60
–60
AMPLITUDE (dB)
0
–80
–100
–120
–80
–100
–120
–140
–140
–160
–160
–180
–180
–200
–200
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
FREQUENCY (kHz)
4.0
4.5
5.0
11773-019
AMPLITUDE (dB)
4.0
–80
–140
10
3.0
2.5
2.0
3.5
FREQUENCY (kHz)
–100
6
5
1.5
Figure 20. ADC Output FFT; 1 kHz Input Tone, −6 dBFS Input FFT
(Output Data Rate = 10 kSPS, External Reference,
External Clock, Buffers Enabled)
Figure 17. RMS Noise vs. Common-Mode Input Voltage
0
1.0
0.5
11773-020
1
–120
–140
0
0
–100
11773-021
2
–80
0
2
4
6
8
10
12
14
FREQUENCY (kHz)
Figure 22. ADC Output FFT; 1 kHz Input Tone, −6 dBFS Input FFT
(Output Data Rate = 31.25 kSPS, External Reference,
External Clock, Buffers Enabled)
Figure 19. ADC Output FFT; 1 kHz Input Tone, −0.5 dBFS Input FFT
(Output Data Rate = 10 kSPS, External Reference,
External Clock, Buffers Enabled)
Rev. 0 | Page 13 of 64
11773-022
4
11773-017
RMS NOISE (µV)
10
AD7173-8
Data Sheet
1.0
0
UNIT 1 BUFFERS OFF
UNIT 1 BUFFERS ON
UNIT 2 BUFFERS OFF
UNIT 2 BUFFERS ON
UNIT 3 BUFFERS OFF
UNIT 3 BUFFERS ON
–20
0.5
–40
REJECTION (dB)
ERROR (%)
FROM POWER-DOWN
0
FROM STANDBY – REFERENCE OFF
–60
–80
–100
–0.5
0.001
0.0001
0.01
0.1
TIME (Seconds)
–140
11773-023
–1.0
0.00001
50k
0
150k
100k
200k
FREQUENCY (Hz)
11773-026
–120
Figure 26. Common-Mode Rejection Ratio vs. Frequency
(Output Data Rate = 31.25 kSPS)
Figure 23. Internal Reference Settling Time
0.10
0
–20
UNIT
UNIT
UNIT
UNIT
0.05
REJECTION (dB)
ERROR (%)
–40
0
1 BUFFERS OFF
1 BUFFERS ON
2 BUFFERS OFF
2 BUFFERS ON
–60
–80
–100
–0.05
0
10
20
30
40
50
TIME (Seconds)
–100
–105
UNIT 1 BUFFERS OFF
UNIT 1 BUFFERS ON
UNIT 2 BUFFERS ON
UNIT 3 BUFFERS ON
REJECTION (dB)
–115
–120
–125
–130
–140
20
30
40
FREQUENCY (Hz)
50
60
70
11773-025
–135
10
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 27. Power Supply Rejection Ratio vs. Frequency
Figure 24. Internal Reference Settling Time (Extended)
–110
–140
Figure 25. Common-Mode Rejection Ratio (10 Hz to 70 Hz) vs. Frequency
(20 SPS Enhanced Filter)
Rev. 0 | Page 14 of 64
10M
11773-027
–0.10
11773-024
–120
Data Sheet
AD7173-8
6
10
9
INL ERROR (ppm)
8
4
3
2
0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
6
5
4
2
1
5.0
0
–40 –30 –20 –10
REFERENCE VOLTAGE (V)
0
10 20 30 40 50 60
70 80
90 100
TEMPERATURE (°C)
Figure 28. Integral Nonlinearity (INL) Error vs. Reference Voltage
(Differential Input, External Reference)
11773-031
1
7
3
BUFFER ON, DEVICE 1
BUFFER OFF, DEVICE 1
BUFFER ON, DEVICE 2
BUFFER OFF, DEVICE 2
BUFFER ON, DEVICE 3
BUFFER OFF, DEVICE 3
11773-028
INL ERROR (ppm)
5
Figure 31. Integral Nonlinearity (INL) Error vs. Temperature
(Differential Input, VREF = 2.5 V)
30
16.02
16.00
15.98
20
FREQUENCY (Hz)
OCCURRENCE
25
15
10
15.96
15.94
15.92
15.90
DEVICE 1
DEVICE 2
DEVICE 3
15.88
15.86
5
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
INL ERROR (ppm)
15.82
–40
11773-029
0
–20
0
20
40
60
80
100
TEMPERATURE (°C)
Figure 29. Integral Nonlinearity (INL) Distribution Histogram
(Differential Input, VREF = 2.5 V External)
11773-032
15.84
Figure 32. Internal Oscillator Frequency vs. Temperature
2.5010
25
2.5008
2.5006
REFERENCE VOLTAGE (V)
15
10
2.5004
2.5002
2.5000
2.4998
DEVICE 1
DEVICE 2
DEVICE 3
2.4996
2.4994
5
0
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2
INL ERROR (ppm)
2.4990
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
Figure 30. Integral Nonlinearity (INL) Distribution Histogram
(Differential Input, VREF = 5 V External)
Figure 33. Internal Reference Voltage vs. Temperature
Rev. 0 | Page 15 of 64
100
11773-033
2.4992
11773-030
OCCURRENCE
20
AD7173-8
Data Sheet
16
9
14
8
7
OCCURRENCE
OCCURRENCE
12
10
8
6
6
5
4
3
4
0
–48 –46 –44 –42 –40 –38 –36 –34 –32 –30 –28 –26 –24 –22 –20 –18
VOLTAGE (µV)
0
–0.08
–0.06
–0.04
–0.02
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
0.32
0.34
0.36
0.38
0.40
11773-034
1
GAIN ERROR DRIFT (ppm/°C)
Figure 34. Offset Error Distribution Histogram
(Internal Short)
11773-037
2
2
Figure 37. Gain Error Drift Distribution Histogram
6
7
6
5
CURRENT (mA)
4
3
4
3
DEVICE 1
DEVICE 2
DEVICE 3
2
2
1
1
300
350
400
450
OFFSET DRIFT (nV/°C)
0
–40 –30 –20 –10
11773-035
0
250
0
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
Figure 35. Offset Error Drift Distribution Histogram
(Internal Short)
11773-038
OCCURRENCE
5
Figure 38. Current Consumption vs. Temperature
(Continuous Conversion Mode, Buffers Enabled,
Internal Reference, Internal Clock)
35
5.0
4.5
30
4.0
CURRENT (µA)
3.5
20
15
3.0
2.5
2.0
DEVICE 1
DEVICE 2
DEVICE 3
1.5
10
1.0
5
3.0
11773-036
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
–0.2
–0.6
–1.0
–1.4
GAIN ERROR (ppm)
0
–40 –30 –20 –10
0
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
Figure 39. Current Consumption vs. Temperature
(Power-Down Mode)
Figure 36. Gain Error Distribution Histogram
Rev. 0 | Page 16 of 64
11773-039
0.5
0
–1.8
OCCURRENCE
25
Data Sheet
AD7173-8
NOISE PERFORMANCE AND RESOLUTION
Table 6 shows the rms noise, peak-to-peak noise, effective
resolution, and the noise free (peak-to-peak) resolution of the
AD7173-8 for various output data rates and filters. The values
listed are for the bipolar input range with an external 5 V
reference.
These values are typical and are generated with a differential
input voltage of 0 V when the ADC is continuously converting
on a single channel. It is important to note that the peak-topeak resolution is calculated based on the peak-to-peak noise.
The peak-to-peak resolution represents the resolution for which
there is no code flicker. Using the sinc3 filter at the fastest rate
results in the noise being quantization limited. This limitation
degrades the noise specification at this rate and does not give a
result of 24 bits, no missing codes.
Table 6. RMS Noise and Peak-to-Peak Resolution vs. Output Data Rate using Sinc5 + Sinc1 Filter (Default) 1
Output Data Rate (SPS)
31,250
5208
1007
381
100.5
20.01
5
1.25
1
RMS Noise (µV rms)
8.0
4.5
2.2
1.3
0.71
0.32
0.15
0.07
Sinc5 + Sinc1 Filter (Default)
Peak-to-Peak
Effective Resolution (Bits)
Noise (µV rms)
20.2
67
21.1
30
22.2
15
22.9
8.9
23.8
5.1
24
1.7
24
0.75
24
0.32
Peak-to-Peak
Resolution (Bits)
17.5
18.3
19.3
20.1
21
22.2
23.4
24
Selected rates only; 1000 samples.
Table 7. RMS Noise and Peak-to-Peak Resolution vs. Output Data Rate using Sinc3 Filter 1
Output Data Rate (SPS)
31,250
5208
1008
400.6
100.5
20.01
5
1.25
1
RMS Noise (µV rms)
210
3.6
1.5
1
0.55
0.25
0.11
0.07
Sinc3 Filter
Peak-to-Peak
Effective Resolution (Bits)
Noise (µV rms)
15.5
1665
21.4
28
22.7
12
23.3
6.6
24
3.5
24
1.2
24
0.56
24
0.27
Selected rates only; 1000 samples.
Rev. 0 | Page 17 of 64
Peak-to-Peak
Resolution (Bits)
12.8
18.7
19.9
20.5
21.4
22.4
23.4
24
AD7173-8
GETTING STARTED
The AD7173-8 offers the user a fast settling, high resolution,
multiplexed ADC with high levels of configurability.
•
•
Eight fully differential or 16 single-ended analog inputs.
Cross point mux. Selects any analog input combination as a
pairing to be converted. The signals are routed to the input
buffers and onto the modulator positive or negative input.
ADC input. Selectable as a fully differential input or as
a single-ended input.
Per setup configurability. Up to eight different setups can
be defined. A separate setup can be mapped to each of the
channels. Each setup allows the user to configure the
following:
• Output data rate
• Digital filter mode
• Offset/gain error correction
• Reference source selection (internal/external)
• Analog and reference input buffer enables
• Digital output coding
The AD7173-8 includes two separate linear regulator blocks for
both the analog and digital circuitry. The analog LDO regulates
the AVDD2 supply to 1.8 V, supplying the ADC core. The user
can tie the AVDD1 and AVDD2 supplies together for easiest
connection. If a clean analog supply rail is in the system in the
range of 2 V to 5.5 V (minimum to maximum), the user can
also choose to connect this supply rail to the AVDD2 input,
allowing for lower power dissipation.
16MHz
CX2
CX1
SEE ANALOG INPUT SECTION FOR FURTHER DETAILS
OPTIONAL EXTERNAL
CRYSTAL CIRCUITRY
CAPACITORS
XTAL1 12
2
AIN0/REF2–
XTAL2/CLKIO 13
DOUT/RDY 14
3
DOUT/RDY
AIN1/REF2+
DIN
DIN 15
36
SCLK
SCLK 16
AIN14
CS
CS 17
37
AIN15
1
AIN16
CLKIN
OPTIONAL
EXTERNAL
CLOCK
INPUT
AD7173-8
IOVDD
IOVDD 20
0.1µF
DGND 21
VIN
1
2
4.7µF
VIN
3
REGCAPD 22
NC 7
0.1µF
1µF
0.1µF
ADR44xBRZ
4
GND
5
AVDD1 9
VOUT 6
8
AVDD1
40
0.1µF
4.7µF
0.1µF
REF+
AVDD2
0.1µF
AVDD2 10
39
REF–
0.1µF
REGCAPA 7
AVSS
8
Figure 40. Typical Connection Diagram
Rev. 0 | Page 18 of 64
0.1µF
1µF
11773-040
•
•
The AD7173-8 includes a precision 2.5 V low drift (3.5 ppm/°C)
band gap internal reference. This reference can be selected to
be used for the ADC conversions, reducing the external component count. When enabled, the internal reference is output to
the REFOUT pin and can be used as a low noise biasing voltage
for the external circuitry. An example of this is using the REFOUT
signal to set the input common mode for an external single-ended
to differential amplifier.
Data Sheet
AD7173-8
The linear regulator for the digital IOVDD supply performs
a similar function, regulating the input voltage applied at the
IOVDD pin to 1.8 V for the internal digital filtering. The serial
interface signals always operate from the IOVDD supply seen at
the pin. This means that if 3.3 V is applied to the IOVDD pin,
the interface logic inputs and outputs operate at this level.
The AD7173-8 can be used across a wide variety of applications,
providing high resolution and accuracy. A sample of these
scenarios follows:
•
•
•
Fast scanning of analog input channels using the internal
mux
Fast scanning of analog input channels using an external
mux
High resolution at lower speeds in either multichannel or
ADC per channel applications
Single ADC per channel; the fast low latency output allows
further application specific filtering in an external microcontroller, DSP, or FPGA
POWER SUPPLIES
The AD7173-8 device has the ability to operate with AVSS set to
a negative voltage, allowing true bipolar inputs to be applied. This
allows for a fully differential input signal centered around 0 V
and eliminates the need for an external level shifting circuit. For
example, with a 5 V split supply, AVDD1 = 2.5 V and AVSS =
−2.5 V. In this use case, the AD7173-8 internally level shifts the
signals, allowing the digital output to function between DGND
(nominally 0 V) and IOVDD.
When using a split supply for AVDD1 and AVSS, the absolute
maximum ratings must be considered (refer to the Absolute
Maximum Ratings section). Ensure that IOVDD is set below
3.6 V to stay within the absolute maximum rating for the
device.
DIGITAL COMMUNICATION
The AD7173-8 can run from either a 3.3 V or 5 V supply
voltage.
The device has three independent power supply pins: AVDD1,
AVDD2, and IOVDD.
•
•
•
•
Split Supply Operation (AVSS ≠ DGND)
AVDD1 and AVDD2 are referred to AVSS.
AVDD2 powers the internal regulator supplying the ADC.
AVDD1 and AVDD2 can be tied together for convenience.
IOVDD is referred to DGND. The supply sets the interface
logic levels on the SPI interface and powers an internal
regulator for operation of the digital processing.
The AD7173-8 has a 3-wire or 4-wire SPI interface that is
compatible with QSPI™, MICROWIRE®, and DSPs. The interface
operates in SPI Mode 3 and can be operated with CS tied low. In
SPI Mode 3, SCLK idles high, the falling edge of SCLK is the drive
edge, and the rising edge of SCLK is the sample edge. This means
that data is clocked out on the falling/drive edge and data is
clocked in on the rising/sample edge.
Single Supply Operation (AVSS = DGND)
When the AD7173-8 is powered from a single supply that is
connected to AVDD1, the supply can be either 3.3 V or 5 V.
In this configuration, AVSS and DGND can be shorted together
on one single ground plane. With this setup, an external level
shifting circuit is required to use fully differential inputs to shift
the common-mode voltage.
Rev. 0 | Page 19 of 64
DRIVE EDGE
SAMPLE EDGE
11773-041
•
AVDD2 is the input to the internal voltage regulator. Connect
AVDD2 to AVDD1 for convenience. Otherwise, if a separate
supply is available in the system, a voltage from 2 V to 5.5 V can
be applied. IOVDD can range from 2 V to 5.5 V in this unipolar
input configuration.
Figure 41. SPI Mode 3 SCLK Edges
AD7173-8
Data Sheet
Accessing the ADC Register Map
The communications register controls access to the full register
map of the ADC. This register is an 8-bit write only register. On
power-up or after a reset, the digital interface defaults to a state
where it is expecting a write to the communications register;
therefore, all communication begins by writing to the communications register.
8-BIT COMMAND
8 BITS, 16 BITS,
OR 24 BITS OF DATA
CMD
DATA
CS
DIN
The data written to the communications register determines
which register is being accessed and if the next operation is a
read or write. The register address bits (RA[5:0]) determine the
specific register to which the read or write operation applies.
11773-042
SCLK
Figure 42. Writing to a Register
(8-Bit Command with Register Address Followed by Data of 8, 16, or 24 Bits;
Data Length Is Dependent on the Register Selected)
When the read or write operation to the selected register is
complete, the interface returns to its default state, where it
expects a write operation to the communications register.
In situations where interface synchronization is lost, a write
operation of at least 64 serial clock cycles with DIN high returns
the ADC to its default state by resetting the entire part, including
the register contents. Alternatively, if CS is being used with the
digital interface, returning CS high resets the digital interface to
its default state and aborts any current operation.
8-BIT COMMAND
8 BITS, 16 BITS,
24 BITS, OR
32 BITS OUTPUT
CS
CMD
DIN
Figure 42 and Figure 43 illustrate writing to and reading from a
register by first writing the 8-bit command to the communications
register followed by the data for the addressed register.
DOUT/RDY
Reading the ID register is the recommended method for verifying
correct communication with the part. The ID register is a read
only register and contains the value 0x30DX for the AD7173-8.
The communication register and ID register details are described
in Table 8 and Table 9.
DATA
11773-043
SCLK
Figure 43. Reading from a Register
(8-Bit Command with Register Address Followed by Data of 8, 16, or 24 Bits;
Data Length on DOUT Is Dependent on the Register Selected)
Table 8. Communications Register Bit Map
Reg
0x00
Name
COMMS
Bits
[7:0]
Bit 7
WEN
Bit 6
R/W
Bit 5
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
0x00
RW
W
Bit 2
Bit 1
Bit 0
Reset
0x30DX 1
RW
R
RA
Table 9. ID Register Bit Map
Reg
0x07
1
Name
ID
Bits
[15:8]
[7:0]
Bit 4
Bit 3
ID[15:8]
ID[7:0]
X = don’t care.
Rev. 0 | Page 20 of 64
Data Sheet
AD7173-8
CONFIGURATION OVERVIEW
Channel Configuration
After power on-or reset, the AD7173-8 default configuration is
as follows:
The AD7173-8 has 16 independent channels and eight independent setups. The user can select any of the analog input pairs on
any channel, as well as any of the eight setups for any channel,
giving the user full flexibility in the channel configuration. This
also allows per channel configuration when using eight
differential inputs because each channel can have its own
dedicated setup.
•
•
•
Channel configuration. CH0 is enabled, AIN0 is selected
as the positive input, and AIN1 is selected as the negative
input. Setup 0 is selected.
Setup configuration. The input buffers are disabled, and
the external reference is selected.
ADC mode. Continuous conversion mode, the internal
oscillator, and single cycle settling are enabled.
Interface mode. CRC is disabled, and data + status output
is disabled.
Note that only a few of the register setting options are shown;
this list is just an example. For full register information, see the
Register Details section.
Figure 44 shows an overview of the suggested flow for changing
the ADC configuration, divided into the following three blocks:
•
•
•
Channel configuration (see Box A in Figure 44)
Setup configuration (see Box B in Figure 44)
ADC mode and interface mode configuration (see Box C
in Figure 44)
Channel Registers
The channel registers are used to select which of the 17 analog
input pins (AIN0 to AIN16) are used as either the positive analog
input or the negative analog input for that channel. This register
also contains a channel enable/disable bit and the setup selection
bits, which are used to pick which of the eight available setups
are used for this channel.
When the AD7173-8 is operating with more than one channel
enabled, the channel sequencer cycles through the enabled
channels in sequential order, from Channel 0 to Channel 15. If a
channel is disabled, it is skipped by the sequencer. Details of the
channel register for Channel 0 are shown in Table 10.
A
CHANNEL CONFIGURATION
SELECT POSITIVE AND NEGATIVE INPUT FOR EACH ADC CHANNEL
SELECT ONE OF 8 SETUPS FOR ADC CHANNEL
B
SETUP CONFIGURATION
8 POSSIBLE ADC SETUPS
SELECT FILTER ORDER, OUTPUT DATA RATE, AND MORE
C
ADC MODE AND INTERFACE MODE CONFIGURATION
SELECT ADC OPERATING MODE, CLOCK SOURCE,
ENABLE CRC, DATA + STATUS, AND MORE
11773-044
•
Figure 44. Suggested ADC Configuration Flow
Table 10. Channel 0 Register Bit Map
Reg Name
0x10 CH0
Bits Bit 7
[15:8] CH_EN0
[7:0]
Bit 6
Bit 5
Bit 4
SETUP_SEL[2:0]
AINPOS0[2:0]
Bit 3
Rev. 0 | Page 21 of 64
Bit 2
Bit 1
Bit 0
RESERVED
AINPOS0[4:3]
AINNEG0
Reset RW
0x8001 RW
AD7173-8
Data Sheet
ADC Setups
Setup Configuration Registers
The AD7173-8 has eight independent setups. Each setup
consists of the following four registers:
The setup configuration registers allow the user to select the output
coding of the ADC by selecting between bipolar and unipolar. In
bipolar mode, the ADC accepts negative differential input voltages,
and the output coding is offset binary. In unipolar mode, the ADC
accepts only positive differential voltages, and the coding is straight
binary. In either case, the input voltage must be within the AVDD1/
AVSS supply voltages. The user can also select the reference source
using this register. Four options are available: an internal 2.5 V
reference, an external reference connected between the REF+
and REF− pins, an external reference connected between
AIN0/REF2− and AIN1/REF2+, or AVDD1 − AVSS. The
analog input buffers and reference input buffers for the setup
can also be enabled using this register.
•
•
•
•
Setup configuration register
Filter configuration register
Offset register
Gain register
For example, Setup 0 consists of Setup Configuration Register 0,
Filter Configuration Register 0, Offset Register 0, and Gain
Register 0. Figure 45 shows the grouping of these registers The
setup is selectable from the channel registers detailed in the
Channel Configuration section. This allows each channel to be
assigned to one of 8 separate setups. Table 11 through Table 14
show the four registers that are associated with Setup 0. This
structure is repeated for Setup 1 to Setup 7.
Filter Configuration Registers
The filter configuration register selects which digital filter is
used at the output of the ADC modulator. The order of the filter
and the output data rate is selected by setting the bits in this
register. For more information, see the Digital Filters section.
FILTER CONFIG
REGISTERS
SETUP CONFIG
REGISTERS
GAIN REGISTERS*
OFFSET REGISTERS
SETUPCON0 0x20
FILTCON0 0x28
GAIN0
0x38
OFFSET0 0x30
SETUPCON1 0x21
FILTCON1 0x29
GAIN1
0x39
OFFSET1 0x31
SETUPCON2 0x22
FILTCON2 0x2A
GAIN2
0x3A
OFFSET2 0x32
SETUPCON3 0x23
FILTCON3 0x2B
GAIN3
0x3B
OFFSET3 0x33
SETUPCON4 0x24
FILTCON4 0x2C
GAIN4
0x3C
OFFSET4 0x34
SETUPCON5 0x25
FILTCON5 0x2D
GAIN5
0x3D
OFFSET5 0x35
SETUPCON6 0x26
FILTCON6 0x2E
GAIN6
0x3E
OFFSET6 0x36
SETUPCON7 0x27
FILTCON7 0x2F
GAIN7
0x3F
OFFSET7 0x37
AIN BUFFERS
REF BUFFERS
BURNOUT
REFERENCE SOURCE
SELECT DIGITAL
FILTER TYPE
AND OUTPUT DATA RATE
SINC5 + SINC1
SINC3
SINC3 MAP
ENHANCED 50/60
GAIN CORRECTION
OPTIONALLY
PROGRAMMED
PER SETUP AS REQUIRED
(*FACTORY CALIBRATED)
OFFSET CORRECTION
OPTIONALLY PROGRAMMED
PER SETUP AS REQUIRED
11773-045
SELECT PERIPHERAL
FUNCTIONS FOR
ADC CHANNEL
Figure 45. ADC Setup Register Grouping
Table 11. Setup Configuration 0 Register Bit Map
Reg
0x20
Name
Bits
Bit 7
Bit 6
SETUPCON0 [15:8]
RESERVED
[7:0]
BURNOUT_EN0 RESERVED
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
BI_UNIPOLAR0
REF_BUF 0[1:0]
AIN_BUF 0[1:0]
REF_SEL0
RESERVED
Reset
0x1000
RW
RW
Reset
0x0000
RW
RW
Table 12. Filter Configuration 0 Register Bit Map
Reg
0x28
Name
FILTCON0
Bits
Bit 7
SINC3_MAP0
Bit 6
Bit 5
Bit 4
RESERVED
ORDER0
Bit 3
Bit 2
ENHFILTEN0
ODR0
Bit 1
Bit 0
ENHFILT0
Table 13. Offset Configuration 0 Register Bit Map
Reg
0x30
Name
OFFSET0
Bits
[23:0]
Bit[23:0]
OFFSET0[23:0]
Reset
RW
0x800000 RW
Bit[23:0]
GAIN0[23:0]
Reset
RW
0x5XXXX0 RW
Table 14. Gain Configuration 0 Register Bit Map
Reg
0x38
Name
GAIN0
Bits
[23:0]
Rev. 0 | Page 22 of 64
Data Sheet
AD7173-8
Offset Registers
ADC Mode and Interface Mode Configuration
The offset register holds the offset calibration coefficient for the
ADC. The power-on reset value of the offset register is 0x800000.
The offset register is a 24-bit read/write register. The power-on
reset value is automatically overwritten if an internal or system
zero-scale calibration is initiated by the user or if the offset register
is written to by the user.
The ADC mode register and the interface mode register configure
the core peripherals for use by the AD7173-8 and the mode for
the digital interface.
ADC Mode Register
The ADC mode register is used primarily to set the conversion
mode of the ADC to either continuous or single conversion.
The user can also select the standby and power-down modes,
as well as any of the calibration modes. In addition, this register
contains the clock source select bits and the internal reference
enable bits. The reference select bits are contained in the setup
configuration registers (see the ADC Setups section for more
information).
Gain Registers
The gain register is a 24-bit register that holds the gain
calibration coefficient for the ADC. The gain registers are
read/write registers. These registers are configured at power-on
with factory calibrated coefficients. Therefore, every device has
different default coefficients. The default value is automatically
overwritten if a system full-scale calibration is initiated by the
user or if the gain register is written to by the user. For more
information on calibration, see the Operating Modes section.
Interface Mode Register
The interface mode register configures the digital interface
operation. This register allows the user to control data-word
length, CRC enable, data + status read and continuous read mode.
The details of both registers are shown in Table 15 and Table 16.
For more information, see the Digital Interface section.
Table 15. ADC Mode Register Bit Map
Reg
0x01
Name
ADCMODE
Bits
[15:8]
[7:0]
Bit 7
REF_EN
RESERVED
Bit 6
RESERVED
Bit 5
SING_CYC
MODE
Bit 4
Bit 3
RESERVED
Bit 2
CLOCKSEL
Bit 1
Bit 0
DELAY
RESERVED
Reset
0x2000
RW
RW
Reset
0x0000
RW
RW
Table 16. Interface Mode Register Bit Map
Reg
0x02
Name
IFMODE
Bits
[15:8]
[7:0]
Bit 7
CONTREAD
Bit 6
RESERVED
DATA_STAT
Bit 5
REG_CHECK
Bit 4
ALT_SYNC
RESERVED
Bit 3
Bit 2
Bit 1
IOSTRENGTH
RESERVED
CRC_EN
RESERVED
Rev. 0 | Page 23 of 64
Bit 0
DOUT_RESET
WL16
AD7173-8
Data Sheet
Understanding Configuration Flexibility
The most straightforward implementation of the AD7173-8 is to
use eight differential inputs with adjacent analog inputs and run
all of them with the same setup, gain correction, and offset
correction register. In this case, the user selects the following
differential inputs: AIN0/AIN1, AIN2/AIN3, AIN4/AIN5,
AIN6/AIN7, AIN8/AIN9. AIN10/AIN11, AIN12/AIN13,
AIN14/AIN15. In Figure 46, the registers shown in black font
must be programmed for such a configuration. The registers
that are shown in gray font are redundant in this configuration.
Programming the gain and offset registers is optional for any
use case, as indicated by the dashed lines between the register
blocks.
An alternative way to implement these eight fully differential
inputs is by taking advantage of the eight available setups.
Motivation for doing this includes having is a different speed/noise
requirement on some of the eight differential inputs vs. other
inputs, or there may be a specific offset or gain correction for
particular channels. Figure 47 shows how each of the differential
inputs may use a separate setup, allowing full flexibility in the
configuration of each channel.
CHANNEL
REGISTERS
AIN0
CH0
0x10
AIN1
CH1
0x11
AIN2
CH2
0x12
AIN3
CH3
0x13
AIN4
CH4
0x14
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
CH5
CH6
CH7
CH8
CH9
GAIN REGISTERS*
OFFSET REGISTERS
SETUPCON0 0x20
FILTCON0 0x28
GAIN0
0x38
OFFSET0 0x30
SETUPCON1 0x21
FILTCON1 0x29
GAIN1
0x39
OFFSET1 0x31
SETUPCON2 0x22
FILTCON2 0x2A
GAIN2
0x3A
OFFSET2 0x32
SETUPCON3 0x23
FILTCON3 0x2B
GAIN3
0x3B
OFFSET3 0x33
SETUPCON4 0x24
FILTCON4 0x2C
GAIN4
0x3C
OFFSET4 0x34
SETUPCON5 0x25
FILTCON5 0x2D
GAIN5
0x3D
OFFSET5 0x35
SETUPCON6 0x26
FILTCON6 0x2E
GAIN6
0x3E
OFFSET6 0x36
SETUPCON7 0x27
FILTCON7 0x2F
GAIN7
0x3F
OFFSET7 0x37
0x15
0x16
0x17
0x18
0x19
CH10 0x1A
CH11 0x1B
CH12 0x1C
AIN13
CH13 0x1D
AIN14
CH14 0x1E
AIN15
CH15 0x1F
AIN16
FILTER CONFIG
REGISTERS
SELECT ANALOG INPUT PARTS
ENABLE THE CHANNEL
SELECT SETUP 0
SELECT PERIPHERAL
FUNCTIONS FOR
ADC CHANNEL
SELECT DIGITAL
FILTER TYPE
AND OUTPUT DATA RATE
AIN BUFFERS
REF BUFFERS
BURNOUT
REFERENCE SOURCE
31.25kSPS TO 1.25SPS
SINC5 + SINC1
SINC3
GAIN CORRECTION
OFFSET CORRECTION
OPTIONALLY
OPTIONALLY PROGRAMMED
PROGRAMMED
PER SETUP AS REQUIRED
PER SETUP AS REQUIRED
(*FACTORY CALIBRATED)
11773-046
AIN5
SETUP CONFIG
REGISTERS
SINC3 MAP
ENHANCED 50/60
Figure 46. Eight Fully Differential Inputs, All Using a Single Setup (SETUPCON0; FILTCON0; GAIN0; OFFSET0)
CHANNEL
REGISTERS
AIN0
CH0
0x10
AIN1
CH1
0x11
AIN2
CH2
0x12
AIN3
CH3
0x13
AIN4
CH4
0x14
AIN6
AIN7
AIN8
CH5
CH6
CH7
GAIN REGISTERS*
OFFSET REGISTERS
SETUPCON0 0x20
FILTCON0 0x28
GAIN0
0x38
OFFSET0 0x30
SETUPCON1 0x21
FILTCON1 0x29
GAIN1
0x39
OFFSET1 0x31
SETUPCON2 0x22
FILTCON2 0x2A
GAIN2
0x3A
OFFSET2 0x32
SETUPCON3 0x23
FILTCON3 0x2B
GAIN3
0x3B
OFFSET3 0x33
SETUPCON4 0x24
FILTCON4 0x2C
GAIN4
0x3C
OFFSET4 0x34
SETUPCON5 0x25
FILTCON5 0x2D
GAIN5
0x3D
OFFSET5 0x35
SETUPCON6 0x26
FILTCON6 0x2E
GAIN6
0x3E
OFFSET6 0x36
SETUPCON7 0x27
FILTCON7 0x2F
GAIN7
0x3F
OFFSET7 0x37
0x15
0x16
0x17
CH8 0x18
AIN9
CH9 0x19
AIN10
CH10 0x1A
AIN11
CH11 0x1B
AIN12
CH12 0x1C
AIN13
CH13 0x1D
AIN14
CH14 0x1E
AIN15
CH15 0x1F
AIN16
FILTER CONFIG
REGISTERS
SELECT ANALOG INPUT PARTS
ENABLE THE CHANNEL
SELECT SETUP
SELECT PERIPHERAL
FUNCTIONS FOR
ADC CHANNEL
SELECT DIGITAL
FILTER TYPE
AND OUTPUT DATA RATE
AIN BUFFERS
REF BUFFERS
BURNOUT
REFERENCE SOURCE
31.25kSPS TO 1.25SPS
SINC5 + SINC1
SINC3
GAIN CORRECTION
OFFSET CORRECTION
OPTIONALLY
OPTIONALLY PROGRAMMED
PROGRAMMED
PER SETUP AS REQUIRED
PER SETUP AS REQUIRED
(*FACTORY CALIBRATED)
SINC3 MAP
ENHANCED 50/60
Figure 47. Eight Fully Differential Inputs with a Setup per Channel
Rev. 0 | Page 24 of 64
11773-047
AIN5
SETUP CONFIG
REGISTERS
Data Sheet
AD7173-8
Figure 48 shows an example of how the channel registers span
between the analog input pins and the setup configurations
downstream. In this random example, seven differential inputs and
two single-ended inputs are required. The single-ended inputs are
the AIN8/AIN16 and AIN15/AIN16 combinations. The first five
differential input pairs (AIN0/AIN1, AIN2/AIN3, AIN4/AIN5,
AIN6/AIN7, AIN9/AIN10) use the same setup: SETUPCON0.
The two single-ended input pairs (AIN8/AIN16 and AIN15/
AIN16) are set up as a diagnostics; therefore, use a separate setup:
SETUPCON1. The final two differential inputs (AIN11/AIN12
and AIN13/AIN14) also use a separate setup: SETUPCON2.
Given that three setups are selected for use, the SETUPCON0,
SETUPCON1, and SETUPCON2 registers are programmed as
required, and the FILTCON0, FILTCON1, and FILTCON2
registers are also programmed as desired. Optional gain and
offset correction can be employed on a per setup basis by
programming the GAIN0, GAIN1, and GAIN2 registers and
the OFFSET0, OFFSET1, and OFFSET2 registers.
In the example shown in Figure 48, the CH0 to CH8 registers
are used. Setting the MSB in each of these registers, the CH_EN0
to CH_EN8 bits enable the nine combinations via the cross point
mux. When the AD7173-8 converts, the sequencer transitions in
ascending sequential order from CH0 to CH1 to CH2, and then
on to CH8 before looping back to CH0 to repeat the sequence.
CHANNEL
REGISTERS
AIN0
CH0
0x10
AIN1
CH1
0x11
AIN2
CH2
0x12
AIN3
CH3
0x13
AIN4
CH4
0x14
AIN6
AIN7
AIN8
CH5
CH6
CH7
GAIN REGISTERS*
OFFSET REGISTERS
SETUPCON0 0x20
FILTCON0 0x28
GAIN0
0x38
OFFSET0 0x30
SETUPCON1 0x21
FILTCON1 0x29
GAIN1
0x39
OFFSET1 0x31
SETUPCON2 0x22
FILTCON2 0x2A
GAIN2
0x3A
OFFSET2 0x32
SETUPCON3 0x23
FILTCON3 0x2B
GAIN3
0x3B
OFFSET3 0x33
SETUPCON4 0x24
FILTCON4 0x2C
GAIN4
0x3C
OFFSET4 0x34
SETUPCON5 0x25
FILTCON5 0x2D
GAIN5
0x3D
OFFSET5 0x35
SETUPCON6 0x26
FILTCON6 0x2E
GAIN6
0x3E
OFFSET6 0x36
SETUPCON7 0x27
FILTCON7 0x2F
GAIN7
0x3F
OFFSET7 0x37
0x15
0x16
0x17
CH8 0x18
AIN9
CH9 0x19
AIN10
CH10 0x1A
AIN11
CH11 0x1B
AIN12
CH12 0x1C
AIN13
CH13 0x1D
AIN14
CH14 0x1E
AIN15
CH15 0x1F
AIN16
FILTER CONFIG
REGISTERS
SELECT ANALOG INPUT PARTS
ENABLE THE CHANNEL
SELECT SETUP
SELECT PERIPHERAL
FUNCTIONS FOR
ADC CHANNEL
SELECT DIGITAL
FILTER TYPE
AND OUTPUT DATA RATE
AIN BUFFERS
REF BUFFERS
BURNOUT
REFERENCE SOURCE
31.25kSPS TO 1.25SPS
SINC5 + SINC1
SINC3
GAIN CORRECTION
OFFSET CORRECTION
OPTIONALLY
OPTIONALLY PROGRAMMED
PROGRAMMED
PER SETUP AS REQUIRED
PER SETUP AS REQUIRED
(*FACTORY CALIBRATED)
SINC3 MAP
ENHANCED 50/60
Figure 48. Mixed Differential and Single-Ended Configuration Using Multiple Shared Setups
Rev. 0 | Page 25 of 64
11773-048
AIN5
SETUP CONFIG
REGISTERS
AD7173-8
Data Sheet
CIRCUIT DESCRIPTION
this is by using adjacent input pins as the differential pair. All
analog inputs decoupling capacitors connect to AVSS.
ANALOG INPUT
Buffered Analog Input
The AD7173-8 integrates precision unity gain buffers on the
ADC inputs. The output of the integrated cross point mux is
connected to the ADC via these precision buffers. The buffers
provide the benefit of giving the user high input impedance and
fully drive the internal ADC switch capacitor sampling network.
There is a buffer on both the positive and negative analog inputs to
the ADC. The input signals of the AIN pair that is selected via
control of the cross point mux (BUF+, BUF−) pass to the buffer
inputs, which drive the ADC sampling capacitor circuitry. Each
analog input buffer has an input voltage range as shown in
Figure 49. Each buffer can operate with an input signal down to
AVSS (analog ground) or up to an input voltage of 1.1 V from
the AVDD1 supply.
Fully Differential Inputs
The AIN0 to AIN16 analog inputs are connected to a cross point
mux. Any combination of signals can be used to create an analog
input pair. This allows the user to select eight fully differential
inputs or 16 single-ended inputs. If all signals to the AD7173-8
are fully differential, it is recommended that the traces of the inputs
be of the same length. The most reliable and efficient way to do
Single-Ended Inputs
The user can also choose to measure 16 different single-ended
analog inputs. In this case, each of the analog inputs is converted
as being the difference between the single-ended input to be
measured and a set analog input common pin. Because there is
a cross point mux, the user can set any of the analog inputs as the
common pin. An example of such a scenario is to connect the
AIN16 pin to AVSS or to the REFOUT voltage (that is, AVSS +
2.5 V) and select this input when configuring the cross point
mux. When using the AD7173-8 with single-ended inputs, the
INL specification is degraded.
When the user requires a buffered input in either the fully
differential or single-ended case, the user is required to turn on
the analog input buffers as a pair. This means that, even where
an input pin is connected to AVSS, the input buffer of this
channel is turned on if the other pin making up the differential
input is going to be buffered.
AVDD1
1.1V
CROSSPOINT
MULTIPLEXER
USABLE
INPUT VOLTAGE RANGE:
BUFFERS ON
(AVDD1 – 1.1V) – (AVSS)
REF– REF+ REFOUT
AVDD1
AIN X
REFERENCE
INPUT
BUFFERS
INT
REF
ANALOG
INPUT
BUFFERS
ON
BUF+
AIN Y
CS
Σ-Δ ADC
BUF–
DIGITAL
FILTER
ON
SERIAL
INTERFACE
AND CONTROL
SCLK
DIN
DOUT/RDY
AVSS
AVSS
Figure 49. Analog Input Voltage Range with Analog Input Buffers Enabled
Rev. 0 | Page 26 of 64
11773-049
TEMPERATURE
SENSOR
Data Sheet
AD7173-8
0
–50
AMPLITUDE (dB)
Using External Buffers
The analog input buffers can be disabled. When they are disabled,
the input voltage range on the analog inputs is AVDD1 – AVSS.
The analog input switched capacitor input is then exposed to
the user. A suitable external amplifier is required to sufficiently
drive and settle the analog input in such cases. The CS1 and CS2
capacitors each have a magnitude in the order of a number of
picofarads (pF). This capacitance is the combination of both the
sampling capacitance and the parasitic capacitance.
AVDD1
AIN0
–100
–150
–200
–250
0.1
1
10
1k
100
11773-051
Running with Single Cycle = 0
The output data rate can be maximized when using only a single
channel by setting the SING_CYC bit to 0. However, the analog
input current changes in magnitude, depending on the output
data rate selected. In this condition, the input current increases
by approximately 32× for output data rates selected at >2.6 kSPS.
Set the SING_CYC bit to 0 only in this specific use case. Figure 52
and Figure 53 show rms noise and input current vs. output data
rate for various conditions.
The average input current to the AD7173-8 changes linearly
with the differential input voltage at a rate of 6 µA/V. Each
analog input must be buffered externally, not only to provide the
varying input current with differential input amplitude, but also
to settle the switched capacitor input to allow accurate sampling.
The simplified analog input circuit for this situation is shown in
Figure 50.
10k
FREQUENCY (Hz)
Figure 51. Shorted Input FFT
12
10
RMS NOISE (µV)
Buffer Chopping, Noise, and Input Current
Each analog input buffer amplifier is fully chopped, meaning that
it minimizes the offset error drift and 1/f noise of the signal chain.
The 1/f noise profile is shown in Figure 51.
The noise performance of the buffer at certain output data rates
can be improved by increasing the chopping rate of the buffer,
giving a corresponding increase in input current. This is done
by setting the BUFCHOPMAXx bit in the setup configuration
register of the selected setup.
8
6
BUFCHOP MAX = 0
BUFCHOP MAX = 1
4
AVSS
AVDD1
2
Ø1
CS1
0
1
AVSS
10
100
1k
10k
ODR (SPS)
Ø2
Figure 52. RMS Noise vs. Output Data Rate
(Sinc5 + Sinc1 Filter)
Ø2
AVDD1
11773-052
+IN
AIN1
CS2
14
AIN14
12
–IN
AIN15
AVSS
AVDD1
11773-050
AVSS
10
8
SINGLE CHANNEL AND SING_CYC = 0
BUFCHOPMAX = 1
SING_CYC = 1
6
4
2
0
–2
–4
Figure 50. Simplfied Analog Input Circuit
–6
1
10
100
1k
10k
ODR (SPS)
Figure 53. Typical Analog Input Current vs. Output Data Rate
(2.5 V Common Mode)
Rev. 0 | Page 27 of 64
11773-053
AIN16
AVERAGE AIN CURRENT (nA)
AVSS
AVDD1
Ø1
AD7173-8
Data Sheet
REFERENCE OPTIONS
Internal Reference
The AD7173-8 offers the user the option of either supplying an
external reference to the REF+ and REF− pins of the device or
allowing the use of the internal 2.5 V, low noise, low drift reference.
Select the reference source to be used by the analog input by setting
the REF_SELx bits (Bits[5:4]) in the setup configuration registers
appropriately. The structure of the Setup Configuration 0 register
is shown in Table 17. The AD7173-8 defaults on power-up to
use of an external reference.
The AD7173-8 includes its own low noise, low drift voltage
reference. On power-up, the internal reference is disabled by
default and a register write is required to select it as the reference
source for the ADC. Write to the REF_EN bit (Bit 15) in the ADC
mode register to enable it (see Table 18). The internal reference
has a 2.5 V output and is output on the REFOUT pin after the
REF_EN bit is set in the ADC mode register. Decouple the internal
reference to AVSS with a 0.1 µF capacitor.
External Reference
The REFOUT signal is buffered prior to being output to the pin.
The signal can be used externally in the circuit as a common-mode
source for external amplifier configurations.
The AD7173-8 has a fully differential reference input applied
through the REF+ and REF− pins. Standard low noise, low drift
voltage references, such as the ADR445, ADR444, and ADR441,
are recommended for use. Apply the external reference to the
AD7173-8 reference pins as shown in Figure 54. Decouple the
output of any external reference is to AVSS. As shown in
Figure 54, the ADR441 output is decoupled with a 0.1 µF
capacitor at its output for stability purposes. The output is then
connected to a 4.7 µF capacitor, which acts as a reservoir for any
dynamic charge required by the ADC, and followed by a 0.1 µF
decoupling capacitor at the REF+ input. This capacitor is placed
as close as possible to the REF+ and REF− pins. The REF− pin is
connected directly to the AVSS potential.
CLOCK SOURCE
The AD7173-8 requires a master clock of 2 MHz. The AD7173-8
can use one of the following sources as its sampling clock:
•
•
Internal oscillator
External crystal (use a 16 MHz crystal, automatically
divided internally to set the 2 MHz clock)
External clock source
•
All output data rates listed in the data sheet relate to a master clock
rate of 2 MHz. Using a lower clock frequency from, for example,
an external source proportionally scales any listed data rate. To
achieve the specified data rates, particularly rates for rejection
of 50 Hz and 60 Hz, a use a 2 MHz clock. The source of the master
clock is selected by setting the CLOCKSEL bits in the ADCMODE
register, as shown in Table 25. The default, on power-up and reset,
is to operate with the internal oscillator.
AD7173-8
3V TO 18V
ADR441**
40
REF+
39
REF–
0.1µF
0.1µF
*
2.5V VREF
0.1µF
*
*
4.7µF
*
*
11773-054
*ALL DECOUPLING IS TO AVSS.
**ANY OF THE ADR44x FAMILY REFERENCES CAN BE USED.
ADR441 ENABLES REUSE OF THE 3.3V ANALOG SUPPLY
NEEDED FOR AVDD1 TO POWER THE REFERENCE VIN.
Figure 54. External Reference ADR441 Connected to AD7173-8 Reference Pins
Table 17. Setup Configuration 0 Register
Reg
Name
0x20
SETUPCON0 [15:8]
RESERVED
[7:0] BURNOUT_EN RESERVED
Bits
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
RESERVED BI_UNIPOLAR
REF_SEL0
Bit 2
Bit 1
Bit 0
REF_BUF 0[1:0]
AIN_BUF 0[1:0]
RESERVED
Reset
RW
0x1000
RW
0
Reset
0x2000
RW
RW
Table 18. ADC Mode Register
Reg Name
0x01 ADCMODE
Bits Bit 7
Bit 6
[15:8] INT_REF_EN RESERVED
[7:0] RESERVED
Bit 5
SING_CYC
MODE
Bit 4
Bit 3
RESERVED
Rev. 0 | Page 28 of 64
Bit 2
CLOCKSEL
Bit 1
Bit 0
DELAY
RESERVED
Data Sheet
AD7173-8
The internal oscillator is used as the ADC master clock by
default. The clock used for the ADC sampling is 2 MHz (this is
divided down from a higher frequency in the case of the internal
oscillator use). It is the default clock source for the AD7173-8 and
is specified with an accuracy of ±2.5%.
There is an option to allow the internal clock oscillator to be
output on the XTAL2/CLKIO pin. The clock output is driven
to the IOVDD logic level. Use of this option may affect the dc
performance of the AD7173-8 due to a disturbance that may be
introduced by the output driver. The extent to which the performance is affected depends on the IOVDD voltage supply.
Higher IOVDD voltages create a wider logic output swing from
the driver and may affect performance to a greater extent. This
effect may be further exaggerated if the IOSTRENGTH bit
(Register 0x02, Bit 11) is set at higher IOVDD levels (see Table 26
for more information).
External Crystal
If higher precision, lower jitter clock sources are required, the
AD7173-8 has the ability to use an external crystal to generate
the master clock. For the AD7173-8 the required crystal
frequency is 16 MHz. Internally this is automatically divided to
create the 2 MHz needed for sampling the ADC input.
The crystal is connected to the XTAL1 and XTAL2/CLKIO
pins. A recommended crystal for use is the FA-20H: a 16 MHz,
10 ppm, 9 pF crystal from Epson-Toyocom, which is available
in a surface-mounted package.
As shown in Figure 55, allow two capacitors to be inserted from
the traces connecting the crystal to the XTAL1 and XTAL2/CLKIO
pins. These capacitors enable circuit tuning. Connect these
capacitors to the DGND pin. The value for these capacitors
depends on the length and capacitance of the trace connections
between the crystal and the XTAL1 and XTAL2/CLKIO pins.
Therefore, the values of these capacitors differ depending on the
PCB layout and the crystal employed. As a result, empirical
testing of the circuit is required.
AD7173-8
*
CX1
XTAL1 12
CLKIO/XTAL2 13
CX2
*
*DECOUPLE TO GND
11773-055
Internal Oscillator
Figure 55. External Crystal Connections
External Clock
The AD7173-8 can also use an externally supplied clock. In
systems where this is desirable, the external clock is routed
to the XTAL2/CLKIO pin. In this configuration, the XTAL2/
CLKIO pin accepts the externally sourced clock and routes it to
the modulator. The logic level of this clock input is defined by
the voltage applied to the IOVDD pin.
Rev. 0 | Page 29 of 64
AD7173-8
Data Sheet
DIGITAL FILTERS
can be varied to control the final ADC output data rate. Figure 57
shows the frequency domain response of the sinc5 + sinc1 filter at
a 50 SPS output data rate. The sinc5 + sinc1 filter has a slow roll-off
over frequency and narrow notches.
The AD7173-8 provides the following three flexible filter
options to allow optimization of settling time, noise, and
rejection:
Sinc5 + sinc1 filter
Sinc3 filter
Enhanced 50 Hz and 60 Hz rejection filters
SINC1
–20
50Hz AND 60Hz
REJECTION
FILTERS
11773-056
SINC5
0
SINC3
–40
FILTER GAIN (dB)
•
•
•
–60
–80
Figure 56. Digital Filter Block Diagram
–120
0
50
100
150
FREQUENCY (Hz)
Figure 57. Sinc5 + Sinc1 Filter Response at 50 SPS ODR
SINC5 + SINC1 FILTER
The sinc5 + sinc1 filter is targeted at fast switching multiplexed
applications and achieves single cycle settling at output data rates
of 2.6 kSPS and lower. The sinc5 block output is fixed at the
maximum rate of 31.25 kSPS, and the sinc1 block output data rate
The output data rates with the accompanying settling time and
rms noise for the sinc5 + sinc1 filter are listed in Table 19.
Table 19. Output Data Rate (ODR), Settling Time (tSETTLE), and Noise Using the Sinc5 + Sinc1 Filter
Default Output
Data Rate
(SPS/Channel);1
SING_CYC = 1 or
with Multiple
Channels Enabled
6211
5181
4444
3115
2597
1007
503.8
381
200.3
100.5
59.52
49.68
20.01
16.63
10
5
2.5
1.25
1
2
Output Data
Rate (SPS);1
SING_CYC = 0 and
Single Channel
Enabled
31,250
15,625
10,417
5208
2597
1007
503.8
381
200.3
100.5
59.52
49.68
20.01
16.63
10
5
2.5
1.25
11773-057
–100
The filter and output data rate are configured by setting the
appropriate bits in the filter configuration register for the
selected setup. See the Register Details section for more
information.
Settling
Time 1
161 µs
193 µs
225 µs
321 µs
385 µs
993 µs
1.99 ms
2.63 ms
4.99 ms
9.95 ms
16.8 ms
20.13 ms
49.98 ms
60.13 ms
100 ms
200 ms
400 ms
800 ms
Notch
Frequency
(Hz)
31250
15625
10417
5208
3890
1156
539
401
206
102
60
50
20
16.67
10
5
2.5
1.25
Noise
(µV rms)
8.0
6.9
6.0
4.5
3.9
2.2
1.5
1.3
0.99
0.71
0.57
0.52
0.32
0.3
0.22
0.15
0.08
0.07
Noise
(µV p-p) 2
67
52
40
30
27
15
11
8.9
6.6
5.1
3.3
3
1.7
1.6
1.1
0.75
0.32
0.32
Effective
Resolution with
5 V Reference
(Bits)
20.2
20.4
20.7
21.1
21.3
22.2
22.7
22.9
23.3
23.8
24
24
24
24
24
24
24
24
Peak-to-Peak
Resolution with
5 V Reference
(Bits)
17.5
17.7
17.9
18.3
18.5
19.3
19.9
20.1
20.5
21
21.4
21.4
22.2
22.4
22.7
23.4
24
24
The settling time (tSETTLE) is rounded to the nearest microsecond (µs). This is reflected in the output data rate and switching rate. Switching rate = 1 ÷ tSETTLE.
1000 samples.
Rev. 0 | Page 30 of 64
Data Sheet
AD7173-8
SINC3 FILTER
The sinc3 filter achieves the best single-channel noise performance
at lower rates and is, therefore, most suitable for single-channel
applications. The sinc3 filter always has a settling time equal to
tSETTLE = 3/Output Data Rate
Figure 58 shows the frequency domain filter response for the
sinc3 filter. The sinc3 filter has good roll-off over frequency and
has wide notches for good notch frequency rejection.
The output data rates with the accompanying settling time and
rms noise for the sinc3 filter are shown in Table 20.
It is possible to fine-tune the output data rate for the sinc3 filter by
setting the SINC3_MAPx bit in the Filter Configuration x register.
If this bit is set, the mapping of the filter register changes to directly
program the decimation rate of the sinc3 filter. All other options
are eliminated. The data rate, when on a single channel, can be
calculated using the following equation:
Output Data Rate =
0
–10
–20
where:
fMOD is the modulator rate and is equal to 1 MHz.
FILTCONx[14:0] is the contents of the filter configuration
register, excluding the MSB.
–30
FILTER GAIN (dB)
f MOD
32 × FILTCONx[14:0]
–40
–50
–60
For example, an output data rate of 50 SPS can be achieved with
SINC3_MAPx enabled by setting the FILTCONx[14:0] bits to
a value of 625.
–70
–80
–90
–100
0
50
100
150
FREQUENCY (Hz)
11773-058
–110
–120
Figure 58. Sinc3 Filter Response
Table 20. Output Data Rate (ODR), Settling Time (tSETTLE), and Noise Using the Sinc3 Filter
Default Output
Data Rate
(SPS/Channel);1
SING_CYC = 1 or
with Multiple
Channels Enabled
10417
5208
3472
1736
868
336
168
133.53
67.76
33.5
19.99
16.67
6.67
5.56
3.33
1.67
0.83
0.42
1
Output Data
Rate (SPS);1
SING_CYC = 0
and Single
Channel Enabled
31,250
15,625
10,417
5208
2,604
1,008
504
400.6
200.3
100.5
59.98
50
20.01
16.67
10
5
2.5
1.25
Settling
Time 1
96 µs
192 µs
288 µs
576 µs
1.15 ms
2.98 ms
5.95 ms
7.49 ms
14.99 ms
29.85 ms
50.02 ms
60 ms
149.93 ms
179.96 ms
300 ms
600 ms
1.2 sec
2.4 sec
Notch
Frequency
(Hz)
31,250
15,625
10,417
5208
2,604
1,008
504
400.6
200.3
100.5
59.98
50
20.01
16.67
10
5
2.5
1.25
Noise
(µV rms)
210
27
7.8
3.6
2.4
1.5
1.1
1
0.73
0.55
0.44
0.42
0.25
0.21
0.16
0.11
0.08
0.07
Noise
(µV p-p)
1665
206
63
28
20
12
8
7.6
5.1
3.5
2.5
2.3
1.2
1.1
0.83
0.56
0.41
0.27
Effective
Resolution with
5 V Reference
(Bits)
15.5
18.5
20.3
21.4
22
22.7
23.1
23.3
23.8
24
24
24
24
24
24
24
24
24
Peak-to-Peak
Resolution with
5 V Reference
(Bits)
12.8
15.7
17.5
18.7
19.2
19.9
20.4
20.5
21.2
21.4
21.6
21.7
22.4
22.6
22.9
23.4
24
24
The settling time (tSETTLE) is rounded to the nearest microsecond (µs). This settling time is reflected in the output data rate and switching rate. Switching rate = 1 ÷ tSETTLE.
Rev. 0 | Page 31 of 64
AD7173-8
Data Sheet
By default, the AD7173-8 is configured with the SING_CYC bit
in the ADC Mode Register. This means that only fully settled data
is output, thus putting the ADC into a single cycle settling mode.
This mode achieves single cycle settling by reducing the output
data rate to be equal to the settling time of the ADC for the selected
output data rate. This bit has no effect with the sinc5 + sinc1 at
output data rates of 2.6 kSPS and lower or when multiple channels
are enabled.
Figure 59 shows the same step on the analog input but with
single cycle settling enabled. At least a single cycle is required
for the output to be fully settled. The output data rate is equal to
the settling time of the filter at the selected output data rate.
ANALOG
INPUT
FULLY
SETTLED
ADC
OUTPUT
1/ODR
Figure 60. Step Input Without Single Cycle Settling
ENHANCED 50 Hz AND 60 Hz REJECTION FILTERS
The enhanced filters are designed to provide rejection of 50 Hz
and 60 Hz simultaneously and to allow the user to trade off settling
time and rejection. These filters can operate up to 27.27 SPS or
can reject up to 90 dB of 50 Hz ± 1 Hz and 60 Hz ± 1 Hz interference. These filters are realized by post filtering the output of
the sinc5 + sinc1 filter. For this reason, the sinc5 + sinc1 filter
must be selected when using the enhanced filters. Table 21 shows
the output data rates with the accompanying settling time,
rejection, and rms noise. Figure 61 to Figure 68 show the
frequency domain plots of the responses from the enhanced filters.
ANALOG
INPUT
FULLY
SETTLED
11773-059
ADC
OUTPUT
tSETTLE
Figure 60 shows a step on the analog input with this mode
disabled, one channel enabled and the Sinc3 filter selected.
At least three cycles are required after the step change for the
output to reach the final settled value. However, the ADC can
then output a new conversion result at the higher rate of 1/ODR.
11773-060
SINGLE CYCLE SETTLING
Figure 59. Step Input with Single Cycle Settling
Table 21. Enhanced Filter Output Data Rate (ODR), Noise, Settling Time (tSETTLE), and Rejection Using the Enhanced Filters
Output
Data
Rate (SPS)
27.27
25
20
16.67
1
Settling
Time (ms)
Simultaneous
Rejection of
50 Hz ± 1 Hz and
60 Hz ± 1 Hz (dB) 1
Noise
(µV rms)
Noise
(µV p-p)
Effective
Resolution (Bits)
Peak-to-Peak
Resolution (Bits)
Reference
36.67
40.0
50.0
60.0
47
62
85
90
0.45
0.44
0.41
0.41
3.6
3.6
3.0
3.0
24.4
24.4
24.5
24.5
21.4
21.4
21.7
21.7
See Figure 61 and Figure 64
See Figure 62 and Figure 65
See Figure 63 and Figure 66
See Figure 67 and Figure 68
Master clock = 2 MHz.
Rev. 0 | Page 32 of 64
Data Sheet
AD7173-8
0
–10
–20
–20
–30
–30
–40
–50
–60
–40
–50
–60
–70
–70
–80
–80
–90
–90
–100
200
300
400
500
600
FREQUENCY (Hz)
–100
40
–20
–20
–30
–30
FILTER GAIN (dB)
0
–10
–40
–50
–60
–80
–90
–90
–100
–100
40
500
600
FREQUENCY (Hz)
–10
–20
–20
–30
–30
FILTER GAIN (dB)
–10
–40
–50
–60
–80
–90
–90
–100
500
FREQUENCY (Hz)
65
70
–60
–80
400
60
–50
–70
300
55
–40
–70
600
11773-063
FILTER GAIN (dB)
0
200
50
Figure 65. 25 SPS ODR, 40 ms Settling Time
0
100
45
FREQUENCY (Hz)
Figure 62. 25 SPS ODR, 40 ms Settling Time
0
70
–60
–70
400
65
–50
–80
300
60
–40
–70
11773-062
FILTER GAIN (dB)
0
200
55
Figure 64. 27.27 SPS ODR, 36.67 ms Settling Time
–10
100
50
FREQUENCY (Hz)
Figure 61. 27.27 SPS ODR, 36.67 ms Settling Time
0
45
11773-065
100
Figure 63. 20 SPS ODR, 50 ms Settling Time
–100
40
45
50
55
60
65
FREQUENCY (Hz)
Figure 66. 20 SPS ODR, 50 ms Settling Time
Rev. 0 | Page 33 of 64
70
11773-066
0
11773-064
FILTER GAIN (dB)
0
–10
11773-061
FILTER GAIN (dB)
50 Hz and 60 Hz Rejection Filter Frequency Domain Plots
Data Sheet
0
–10
–10
–20
–20
–30
–30
–40
–50
–60
–40
–50
–60
–70
–70
–80
–80
–90
–90
–100
–100
40
0
100
200
300
400
500
FREQUENCY (Hz)
600
Figure 67. 16.667 SPS ODR, 60 ms Settling Time
45
50
55
60
65
FREQUENCY (Hz)
Figure 68. 16.667 SPS ODR, 60 ms Settling Time
Rev. 0 | Page 34 of 64
70
11773-068
FILTER GAIN (dB)
0
11773-067
FILTER GAIN (dB)
AD7173-8
Data Sheet
AD7173-8
OPERATING MODES
CONTINUOUS CONVERSION MODE
Continuous conversion (see Figure 69) is the default power-up
mode. The AD7173-8 converts continuously, and the RDY bit
in the status register goes low each time a conversion is complete.
If CS is low, the DOUT/RDY line also goes low when a conversion
is complete. To read a conversion, the user writes to the
communications register, indicating that the next operation is a
read of the data register. When the data-word has been read from
the data register, DOUT/RDY goes high. The user can read this
register additional times, if required. However, the user must
ensure that the data register is not being accessed at the
completion of the next conversion.
When several channels are enabled, the ADC automatically
sequences through the enabled channels, performing one
conversion on each channel. When all channels are converted,
the sequence starts again with the first channel. The channels
are converted, in order, from lowest enabled channel to highest
enabled channel. The data register is updated as soon as each
conversion is available. The DOUT/RDY pin pulses low each
time a conversion is available. The user must then read the
conversion result while the ADC converts the next enabled
channel; otherwise, the new conversion result is lost.
If the DATA_STAT bit in the interface mode register is set to 1,
the contents of the status register, along with the conversion data,
are output each time the data register is read. The status register
indicates the channel to which the conversion corresponds.
CS
0x44
0x44
DIN
DATA
DATA
11773-069
DOUT/RDY
SCLK
Figure 69. Continuous Conversion Mode
Rev. 0 | Page 35 of 64
AD7173-8
Data Sheet
CONTINUOUS READ MODE
To enable continuous read mode, set the CONTREAD bit in the
interface mode register. When this bit is set, the only serial interface
operations possible are reads from the data register. To exit continuous read mode, issue a dummy read of the ADC data register
command (0x44) while RDY is low. Alternatively, apply a software
reset, that is, 64 SCLKs with CS = 0 and DIN = 1. This resets the
ADC and all register contents. These are the only commands
that the interface recognizes after it is placed in continuous read
mode. Hold DIN low in continuous read mode until an instruction
is to be written to the device.
In continuous read mode (see Figure 70), it is not required that
the communications register be written to before the ADC data
is read. Instead, apply the required number of SCLKs after
DOUT/RDY goes low to indicate the end of a conversion.
When the conversion is read, DOUT/RDY returns high until
the next conversion is available. In this mode, the data can be
read only once. The user must also ensure that the data-word is
read before the next conversion is complete. If the user has not
read the conversion before the completion of the next conversion
or if insufficient serial clocks are applied to the AD7173-8 to
read the word, the serial output register is reset shortly before the
next conversion is complete, and the new conversion is placed in
the output serial register. To use continuous read mode, the
ADC must be configured for continuous conversion mode.
If multiple ADC channels are enabled, each channel is output
in turn, with the status bits being appended to the data if the
DATA_STAT bit is set in the interface mode register. The status
register indicates the channel to which the conversion corresponds.
CS
0x02
0x0080
DIN
DATA
DATA
DATA
11773-070
DOUT/RDY
SCLK
Figure 70. Continuous Read Mode
Rev. 0 | Page 36 of 64
Data Sheet
AD7173-8
SINGLE CONVERSION MODE
In single conversion mode (see Figure 71), the AD7173-8
performs a single conversion and is placed in standby mode
after the conversion is complete. DOUT/RDY goes low to indicate
the completion of a conversion. After the data-word is read from
the data register, DOUT/RDY goes high. The data register can
be read several times, if required, even when DOUT/RDY is high.
If several channels are enabled, the ADC automatically sequences
through the enabled channels and performs a conversion on each
channel. When a conversion is started, DOUT/RDY goes high and
remains high until a valid conversion is available and CS is low. As
soon as the conversion is available, DOUT/RDY goes low. The
ADC then selects the next channel and begins a conversion. The
user must read the present conversion while the next conversion is
being performed. As soon as the next conversion is complete,
the data register is updated; therefore, the period in which to
read the conversion is limited. After the ADC performs a single
conversion on each of the selected channels, it returns to
standby mode.
If the DATA_STAT bit in the interface mode register is set to 1,
the contents of the status register, along with the conversion, are
output each time the data register is read. The four LSBs of the
status register indicate the channel to which the conversion
corresponds.
CS
0x01
0x2010
0x44
DIN
DATA
11773-071
DOUT/RDY
SCLK
Figure 71. Single Conversion Mode
Rev. 0 | Page 37 of 64
AD7173-8
Data Sheet
STANDBY AND POWER-DOWN MODES
In standby mode, most blocks are powered down. The LDOs
remain active such that the registers maintain their contents.
The internal reference remains active, if enabled; and the crystal
oscillator remains active, if selected. To power down the
reference in standby mode, set the REF_EN bit in the ADC
mode register to 0. To power down the clock in standby mode,
set the CLOCKSEL bits in the ADC mode register to 00
(internal oscillator).
In power-down mode, all blocks are powered down, including
the LDOs. All registers lose their contents, and the GPIO outputs
are placed in tristate. To prevent accidental entry to power-down
mode, the ADC must first be placed into standby mode. Exiting
power-down mode requires 64 SCLKs with CS = 0 and DIN = 1,
that is, a serial interface reset. A delay of 500 µs is recommended
before issuing a subsequent serial interface command to allow
the LDO to power up.
CALIBRATION MODES
The AD7173-8 provides three calibration modes that can be
used to eliminate the offset and gain errors on a per setup basis:
•
•
•
Internal zero-scale calibration mode
System zero-scale calibration mode
System full-scale calibration mode
Only one channel can be active during calibration. After each
conversion, the ADC conversion result is scaled using the ADC
calibration registers before being written to the data register.
The default value of the offset register is 0x800000, and the
nominal value of the gain register is 0x555555. The calibration
range of the ADC gain is from 0.4 × VREF to 1.05 × VREF. The
following equations show the calculations that are used. In
unipolar mode, the ideal relationship—that is, not taking into
account the ADC gain error and offset error—is as follows:
 0.75 × VIN

Gain
Data = 
× 2 23 − (Offset − 0x800000) ×
×2
 VREF
 0x400000
In bipolar mode, the ideal relationship—that is, not taking into
account the ADC gain error and offset error—is as follows:
 0.75 × VIN

Gain
Data = 
× 223 − (Offset − 0x800000) ×
+ 0x800000
 VREF
 0x400000
To start a calibration, write the relevant value to the MODE bits
in the ADC mode register. The DOUT/RDY pin and the RDY bit
in the status register go high when the calibration initiates. When
the calibration is complete, the contents of the corresponding
offset or gain register are updated, the RDY bit in the status
register is set, the DOUT/RDY pin returns low (if CS is low),
and the AD7173-8 reverts to standby mode.
During an internal offset calibration, the selected positive
analog input pin is disconnected, and both modulator inputs
are connected internally to the selected negative analog input
pin. For this reason, it is necessary to ensure that the voltage on
the selected negative analog input pin does not exceed the
allowed limits and is free from excessive noise and interference.
System calibrations, however, expect the system zero-scale
(offset) and system full-scale (gain) voltages to be applied to the
ADC pins before initiating the calibration modes. As a result,
errors external to the ADC are removed.
From an operational point of view, treat a calibration like
another ADC conversion. An offset calibration, if required,
must always be performed before a full-scale calibration. Set the
system software to monitor the RDY bit in the status register or
the DOUT/RDY pin to determine the end of a calibration via a
polling sequence or an interrupt-driven routine. All calibrations
require a time that is equal to the settling time of the selected
filter and the output data rate to be completed.
An internal offset calibration, system zero-scale calibration, and
system full-scale calibration can be performed at any output data
rate. Using lower output data rates results in better calibration
accuracy and is accurate for all output data rates. A new calibration
is required for a given channel if the reference source for that
channel is changed.
The offset error is typically ±40 µV, and an offset calibration
reduces the offset error to the order of the noise. The gain error
is factory calibrated at ambient temperature. Following this
calibration, the gain error is typically ±0.001%.
The AD7173-8 provides the user with access to the on-chip
calibration registers, allowing the microprocessor to read the
calibration coefficients of the device and to write its own
calibration coefficients. A read or write of the offset and gain
registers can be performed at any time except during an internal
or self calibration.
Rev. 0 | Page 38 of 64
Data Sheet
AD7173-8
DIGITAL INTERFACE
Figure 2 and Figure 3 show timing diagrams for interfacing to
the AD7173-8 using CS to decode the part. Figure 2 shows the
timing for a read operation from the AD7173-8, and Figure 3
shows the timing for a write operation to the AD7173-8. It is
possible to read from the data register several times, even though
the DOUT/RDY line returns high after the first read operation.
However, take care to ensure that the read operations are completed
before the next output update occurs. In continuous read mode,
the data register can be read only once.
The serial interface can operate in 3-wire mode by tying CS low.
In this case, the SCLK, DIN, and DOUT/RDY lines are used to
communicate with the AD7173-8. The end of the conversion
can also be monitored using the RDY bit in the status register.
The serial interface can be reset by writing 64 SCLKs with CS =
0 and DIN = 1. A reset returns the interface to the state in which it
expects a write to the communications register. This operation
resets the contents of all registers to their power-on values.
Following a reset, allow a period of 500 µs before addressing the
serial interface.
CHECKSUM PROTECTION
The AD7173-8 has a checksum mode that can be used to improve
interface robustness. Using the checksum ensures that only
valid data is written to a register and allows data read from
a register to be validated. If an error occurs during a register
write, the CRC_ERROR bit is set in the status register. However,
For CRC checksum calculations during a write operation, the
following polynomial is always used:
x8 + x2 + x + 1
During read operations, the user can select between this
polynomial and a similar XOR function. The XOR function
requires less time to process on the host microcontroller than
the polynomial-based checksum. The CRC_EN bits in the
interface mode register enable and disable the checksum and
allow the user to select between the polynomial check and the
simple XOR check.
The checksum is appended to the end of each read and write
transaction. The checksum calculation for the write transaction
is calculated using the 8-bit command word and the 8- to 24-bit
data. For a read transaction, the checksum is calculated using
the command word and the 8- to 32-bit data output. Figure 72
and Figure 73 show SPI write and read transactions, respectively.
8-BIT COMMAND
UP TO 24-BIT INPUT
8-BIT CRC
CMD
DATA
CRC
CS
DIN
11773-072
The DOUT/RDY pin also functions as a data-ready signal, with
the line going low if CS is low when a new data-word is available
in the data register. The pin is reset high when a read operation
from the data register is complete. The DOUT/RDY pin also goes
high before updating the data register to indicate when not to
read from the device to ensure that a data read is not attempted
while the register is being updated. Take care to avoid reading
from the data register when DOUT/RDY is about to go low. The
best method to ensure that no data read occurs is to always monitor
the DOUT/RDY line; start reading the data register as soon as
DOUT/RDY goes low; and ensure a sufficient SCLK rate, such
that the read is completed before the next conversion result. CS is
used to select a device. It can be used to decode the AD7173-8
in systems where several components are connected to the
serial bus.
to ensure that the register write was successful, it is important to
read back the register and verify the checksum.
SCLK
Figure 72. SPI Write Transaction with CRC
8-BIT COMMAND
UP TO 32-BIT OUTPUT
8-BIT CRC
CS
DIN
DOUT/
RDY
CMD
DATA
CRC
SCLK
11337-073
The programmable functions of the AD7173-8 are via the SPI
serial interface. The serial interface of the AD7173-8 consists of
four signals: CS, DIN, SCLK, and DOUT/RDY. The DIN line is
used to transfer data into the on-chip registers, and DOUT/RDY is
used to access data from the on-chip registers. SCLK is the serial
clock input for the device, and all data transfers (either on DIN or
on DOUT/RDY) occur with respect to the SCLK signal.
Figure 73. SPI Read Transaction with CRC
If checksum protection is enabled when continuous read mode
is active, there is an implied read data command of 0x44 before
every data transmission that must be accounted for when
calculating the checksum value. This ensures a nonzero checksum
value even if the ADC data equals 0x000000.
Rev. 0 | Page 39 of 64
AD7173-8
Data Sheet
CRC CALCULATION
Polynomial
The checksum, which is eight bits wide, is generated using the
following polynomial:
x8 + x2 + x + 1
To generate the checksum, the data is left shifted by eight bits to
create a number ending in eight Logic 0s. The polynomial is
aligned such that its MSB is adjacent to the leftmost Logic 1 of
the data. An exclusive OR (XOR) function is applied to the data
to produce a new, shorter number. The polynomial is again aligned
so that its MSB is adjacent to the leftmost Logic 1 of the new result,
and the procedure is repeated. This process is repeated until the
original data is reduced to a value less than the polynomial.
This is the 8-bit checksum.
Example of a Polynomial CRC Calculation—24-Bit Word: 0x654321 (Eight Command Bits and 16-Bit Data)
An example of generating the 8-bit checksum using the polynomial based checksum is as follows:
Initial value
011001010100001100100001
x +x +x+1
8
2
01100101010000110010000100000000
left shifted eight bits
=
polynomial
100000111
100100100000110010000100000000
100000111
XOR result
polynomial
100011000110010000100000000
100000111
XOR result
polynomial
11111110010000100000000
100000111
XOR result
polynomial value
1111101110000100000000
100000111
XOR result
polynomial value
111100000000100000000
100000111
XOR result
polynomial value
11100111000100000000
100000111
XOR result
polynomial value
1100100100100000000
100000111
XOR result
polynomial value
100101010100000000
100000111
XOR result
polynomial value
101101100000000
100000111
1101011000000
100000111
101010110000
100000111
1010001000
100000111
10000110
XOR result
polynomial value
XOR result
polynomial value
XOR result
polynomial value
XOR result
polynomial value
checksum = 0x86.
Rev. 0 | Page 40 of 64
Data Sheet
AD7173-8
XOR Calculation
The checksum, which is 8-bits wide, is generated by splitting the data into bytes and then performing an XOR of the bytes.
Example of an XOR Calculation—24-Bit Word: 0x654321 (Eight Command Bits and 16-Bit Data)
Using the previous example,
Divide into three bytes: 0x65, 0x43, and 0x21
01100101
0x65
01000011
0x43
00100110
XOR result
00100001
0x21
00000111
CRC
Rev. 0 | Page 41 of 64
AD7173-8
Data Sheet
DIAGNOSTICS
The AD7173-8 has a number of features that can be used for
diagnostic purposes in safety conscious applications as well as
to increase functionality and improve usefulness in a number of
other applications.
GENERAL-PURPOSE I/O
The AD7173-8 has two general-purpose digital input/output
pins (GPIO0, GPIO1) and two general-purpose digital output
pins (GPO2, GPO3). As the naming convention suggests, the
GPIO0 and GPIO1 pins can be configured as inputs or outputs,
but GPO2 and GPO3 are outputs only. The GPIO and GPO pins
are enabled using the following bits in the GPIOCON register:
IP_EN0, IP_EN1 (or OP_EN0, OP_EN1) for GPIO0 and
GPIO1, and OP_EN2_3 for GPO2 and GPO3.
When the GPIO0 or GPIO1 pin is enabled as an input, the logic
level at the pin is contained in the GP_DATA0 or GP_DATA1 bit,
respectively. When the GPIO0, GPIO1, GPO2, or GPO3 pin is
enabled as an output, the GP_DATA0, GP_DATA1, GP_DATA2,
or GP_DATA3 bit, respectively, determines the logic level output
at the pin. The logic levels for these pins are referenced to AVDD1
and AVSS; therefore, outputs have an amplitude of either 5 V or
3.3 V depending on the AVDD1 − AVSS voltage.
If an external mux is used to increase the channel count, the
mux logic pins can be controlled using the AD7173-8 GPIO and
GPO pins. When the MUX_IO bit is set in the GPIOCON
register (Address 0x06, Bit 12), the timing of the GPIO pins is
controlled by the ADC; therefore, the channel change is
synchronized with the ADC, eliminating any need for external
synchronization.
The ERROR pin can also be used as a general-purpose output
if the ERR_EN bits in the GPIOCON register are set to 11. In
this configuration, the ERR_DAT bit in the GPIOCON register
determines the logic level output at the ERROR pin. The logic
level for the pin is referenced to IOVDD and DGND, and
the ERROR pin has an active pull-up.
16-BIT/24-BIT CONVERSIONS
By default, the AD7173-8 generates 24-bit conversions. However,
the width of the conversions can be reduced to 16 bits. Setting
Bit WL16 in the interface mode register to 1 rounds all data
conversions to 16 bits. Clearing this bit sets the width of the
data conversions to 24 bits.
SERIAL INTERFACE RESET (DOUT_RESET)
The serial interface is reset when each read operation is complete.
The instant at which the serial interface is reset is programmable.
By default, the serial interface is reset after a short period of time
following the last SCLK rising edge, the SCLK edge on which
the LSB is read by the processor. By setting the DOUT_RESET
bit to 1 in the interface mode register, the instant at which the
interface is reset is controlled by the CS rising edge. In this case,
the DOUT/RDY pin continues to output the LSB of the register
being read until CS is taken high. Only on the CS rising edge is
the interface reset. This configuration is useful if the CS signal
is used to frame all read operations. If CS is not used to frame
all read operations, DOUT_RESET must be set to 0 so that the
interface is reset following the last SCLK edge in the read
operation.
SYNCHRONIZATION
Normal Synchronization
When the SYNC_EN bit in the GPIOCON register is set to 1,
the SYNC pin functions as a synchronization pin. The SYNC
input allows the user to reset the modulator and the digital
filter without affecting any of the setup conditions on the part.
This allows the user to start gathering samples of the analog
input from a known point in time, that is, the rising edge
of SYNC. This pin must be low for at least one master clock
cycle to ensure that synchronization occurs. If multiple
channels are enabled, the sequencer is reset to the first enabled
channel.
If multiple AD7173-8 devices are operated from a common
master clock, they can be synchronized so that their data registers
are updated simultaneously. This is normally done after each
AD7173-8 has performed its own calibration or has calibration
coefficients loaded into its calibration registers. A falling edge
on the SYNC pin resets the digital filter and the analog modulator
and places the AD7173-8 into a consistent known state. While
the SYNC pin is low, the AD7173-8 is maintained in this state.
On the SYNC rising edge, the modulator and filter are taken
out of this reset state, and on the next master clock edge, the
part starts to gather input samples again.
The part is taken out of reset on the master clock falling edge
following the SYNC low-to-high transition. Therefore, when
multiple devices are being synchronized, take the SYNC pin
high on the master clock rising edge to ensure that all devices
begin sampling on the master clock falling edge. If the SYNC
pin is not taken high in sufficient time, it is possible to have a
difference of one master clock cycle between the devices; that is,
the instant at which conversions are available differs from part
to part by a maximum of one master clock cycle.
The SYNC pin can also be used as a start conversion command.
In this mode, the rising edge of SYNC starts a conversion, and
the falling edge of RDY indicates when the conversion is complete.
The settling time of the filter must be allowed for each data
register update.
Rev. 0 | Page 42 of 64
Data Sheet
AD7173-8
Alternate Synchronization
Setting Bit ALT_SYNC in the interface mode register to 1 enables
an alternate synchronization scheme. The SYNC_EN bit in the
GPIOCON register must be set to 1 to enable this alternate scheme.
In this mode, the SYNC pin operates as a start conversion command when several channels of the AD7173-8 are enabled.
When SYNC is taken low, the ADC completes the conversion
on the current channel, selects the next channel in the
sequence, and then waits until SYNC is taken high to commence
the conversion. The RDY pin goes low when the conversion is
complete on
the current channel, and the data register is updated with the
corresponding conversion. Therefore, the SYNC command
does not interfere with the sampling on the currently selected
channel but allows the user to control the instant at which the
conversion begins on the next channel in the sequence.
This mode can be used only when several channels are enabled.
It is not recommended to use this mode when a single channel
is enabled.
ERROR FLAGS
The status register contains three error bits—ADC_ERROR,
CRC_ERROR, and REG_ERROR—that flag errors with the
ADC conversion, errors with the CRC check, and errors due to
changes in the registers, respectively. In addition, the ERROR
pin can indicate that an error has occurred.
ADC_ERROR
The ADC_ERROR bit in the status register flags any errors that
occur during the conversion process. The flag is set when an overrange or underrange occurs at the output of the ADC. When an
underrange or overrange occurs, the ADC also outputs all 0s or
all 1s, respectively. This flag is reset only when the underrange
or overrange is removed. It is not reset by a read of the data
register.
CRC_ERROR
If the CRC value that accompanies a write operation does not
correspond with the information sent, the CRC_ERROR flag is
set. The flag is reset as soon as the status register is explicitly read.
REG_ERROR
This flag is used in conjunction with the REG_CHECK bit in
the interface mode register. When the REG_CHECK bit is set,
the AD7173-8 monitors the values in the on-chip registers. If
a bit changes, the REG_ERROR bit is set. Therefore, for writes
to the on-chip registers, ensure that REG_CHECK is set to 0.
When the registers have been updated, the REF_CHK bit can be
set to 1. The AD7173-8 calculates a checksum of the on-chip
registers. If one of the register values has changed, the
REG_ERROR bit is set. If an error is flagged, the REG_CHECK
bit must be set to 0 to clear the REG_ERROR bit in the status
register. The register check function does not monitor the data
register, status register, or interface mode register.
ERROR Pin
The ERROR pin functions as an error input/output pin or a
general-purpose output pin. The ERR_EN bits in the GPIOCON
register determine the function of the pin.
When the ERR_EN bits are set to 10, the pin functions as an
open-drain error output pin. The three error bits in the status
register (ADC_ERROR, CRC_ERROR, and REG_ERROR) are
OR’ed, inverted, and mapped to the ERROR pin. Therefore,
the ERROR pin indicates that an error has occurred. To identify
the error source, read the status register.
When ERR_EN bits are set to 01, the ERROR pin functions as
an error input pin. The error pin of another component can be
connected to the AD7173-8 ERROR pin so that the AD7173-8
indicates when an error occurs on either itself or the external
component. The value on the ERROR pin is inverted and OR’ed
with the errors from the ADC conversion, and the result is
indicated via the ADC_ERROR bit in the status register. The value
of the ERROR pin is reflected in the ERR_DAT bit in the status
register.
The ERROR pin is disabled when the ERR_EN bits are set to 00.
When the ERR_EN1 bits are set to 11, the ERROR pin operates
as a general-purpose output.
DATA_STAT
The contents of the status register can be appended to each
conversion on the AD7173-8. This is a useful function if several
channels are enabled. Each time a conversion is output, the
contents of the status register are appended. The four LSBs of
the status register indicate to which channel the conversion
corresponds. In addition, the user can determine if any errors
are being flagged by the error bits.
IOSTRENGTH BIT
The serial interface can operate with a power supply as low as
2 V. At higher speeds (from 10 MHz to 15 MHz upward), the
DOUT/RDY pin may not have sufficient drive strength if there is
moderate parasitic capacitance on the board. The IOSTRENGTH
bit in the interface mode register increases the drive strength of
the DOUT/RDY pin. It is recommended that this bit be kept to
its default value unless a high frequency SPI SCLK (that is,
~15 MHz upward) is being used.
Rev. 0 | Page 43 of 64
AD7173-8
Data Sheet
GROUNDING AND LAYOUT
The analog inputs and reference inputs are differential and,
therefore, most of the voltages in the analog modulator are
common-mode voltages. The high common-mode rejection of
the part removes common-mode noise on these inputs. The
analog and digital supplies to the AD7173-8 are independent
and separately pinned out to minimize coupling between the
analog and digital sections of the device. The digital filter
provides rejection of broadband noise on the power supplies,
except at integer multiples of the master clock frequency.
with digital ground to prevent radiating noise to other sections
of the board and never run clock signals near the analog inputs.
Avoid crossover of digital and analog signals. Run traces on
opposite sides of the board at right angles to each other. This
reduces the effects of feedthrough on the board. A microstrip
technique is by far the best but is not always possible with a
double-sided board. In this technique, the component side of
the board is dedicated to ground planes, whereas signals are
placed on the solder side.
The digital filter also removes noise from the analog and
reference inputs, provided that these noise sources do not
saturate the analog modulator. As a result, the AD7173-8 is
more immune to noise interference than a conventional high
resolution converter. However, because the resolution of the
AD7173-8 is high and the noise levels from the converter are so
low, take care with regard to grounding and layout.
Good decoupling is important when using high resolution ADCs.
The AD7173-8 has three power supply pins: AVDD1, AVDD2,
and IOVDD. The AVDD1 and AVDD2 pins are referenced to
AVSS, and the IOVDD pin is referenced to DGND. Decouple
AVDD1 and AVDD2 with a 10 µF tantalum capacitor in parallel
with a 0.1 µF capacitor to AVSS on each pin. Place the 0.1 µF
capacitor as near as possible to the device on each supply, ideally
right up against the device. Decouple IOVDD with a 10 µF
tantalum capacitor, in parallel with a 0.1 µF capacitor to DGND.
Decouple all analog inputs to AVSS. If an external reference is
used, decouple the REF+ and REF− pins to AVSS.
The printed circuit board (PCB) that houses the ADC must be
designed so that the analog and digital sections are separated
and confined to certain areas of the board. A minimum etch
technique is generally best for ground planes because it results
in the best shielding.
In any layout, the user must keep in mind the flow of currents
in the system, ensuring that the paths for all return currents are as
close as possible to the paths the currents took to reach their
destinations.
If using the AD7173-8 for split supply operation, a separate plane
must be used for AVSS. As an example, the EVAL-AD7173-8SDZ
customer evaluation board uses a 4-layer PCB, with the largest
central section of Layer 3 used as the AVSS plane. Figure 74 shows
the PCB layout of this layer.
11773-074
Avoid running digital lines under the device because this
couples noise onto the die and allows the analog ground plane
to run under the AD7173-8 to prevent noise coupling. The
power supply lines to the AD7173-8 must use as wide a trace as
possible to provide low impedance paths and reduce glitches on
the power supply line. Shield fast switching signals like clocks
The AD7173-8 also has two on-board LDO regulators—one
that regulates the AVDD2 supply and one that regulates the
IOVDD supply. For the REGCAPA pin, it is recommended that
1 µF and 0.1 µF capacitors to AVSS be used. Similarly, for the
REGCAPD pin, it is recommended that 1 µF and 0.1 µF
capacitors to DGND be used.
Figure 74. EVAL-AD7173-8SDZ, PCB Layer 3
Rev. 0 | Page 44 of 64
Data Sheet
AD7173-8
REGISTER SUMMARY
Table 22. Register Summary
Reg
0x00
Name
COMMS
Bits
[7:0]
Bit 7
WEN
R/W
0x00
STATUS
[7:0]
RDY
0x01
ADCMODE
REF_EN
RESERVED
0x02
0x03
0x04
0x06
0x07
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0x1F
0x20
[15:8]
[7:0]
IFMODE
[15:8]
[7:0]
REGCHECK [23:16]
[15:8]
[7:0]
DATA
[23:0]
GPIOCON
[15:8]
[7:0]
ID
[15:8]
[7:0]
CH0
[15:8]
[7:0]
CH1
[15:8]
[7:0]
CH2
[15:8]
[7:0]
CH3
[15:8]
[7:0]
CH4
[15:8]
[7:0]
CH5
[15:8]
[7:0]
CH6
[15:8]
[7:0]
CH7
[15:8]
[7:0]
CH8
[15:8]
[7:0]
CH9
[15:8]
[7:0]
CH10
[15:8]
[7:0]
CH11
[15:8]
[7:0]
CH12
[15:8]
[7:0]
CH13
[15:8]
[7:0]
CH14
[15:8]
[7:0]
CH15
[15:8]
[7:0]
SETUPCON0 [15:8]
[7:0]
0x21
0x22
SETUPCON1 [15:8]
[7:0]
SETUPCON2 [15:8]
[7:0]
CONTREAD
RESERVED
GP_DATA3
Bit 6
Bit 5
Bit 4
ADC_ERROR
CRC_ERROR
REG_ERROR
RESERVED
SING_CYC
MODE
RESERVED
DATA_STAT
PDSW
GP_DATA2
CH_EN0
AINPOS0[2:0]
CH_EN1
AINPOS1[2:0]
CH_EN2
AINPOS2[2:0]
CH_EN3
AINPOS3[2:0]
CH_EN4
AINPOS4[2:0]
CH_EN5
AINPOS5[2:0]
CH_EN6
AINPOS6[2:0]
CH_EN7
AINPOS7[2:0]
CH_EN8
AINPOS8[2:0]
CH_EN9
AINPOS9[2:0]
CH_EN10
AINPOS10[2:0]
CH_EN11
AINPOS11[2:0]
CH_EN12
AINPOS12[2:0]
CH_EN13
AINPOS13[2:0]
CH_EN14
AINPOS14[2:0]
CH_EN15
AINPOS15[2:0]
RESERVED
BURNOUT_
EN0
BURNOUT_
EN1
BURNOUT_
EN2
BUFCHOPMAX
0
RESERVED
BUFCHOPMAX
1
RESERVED
BUFCHOPMAX
2
Bit 3
Bit 2
RA
RESERVED
Bit 1
Bit 0
Reset
0x00
RW
W
CHANNEL
0x80
R
DELAY
RESERVED
RESERVED
DOUT_RESET
RESERVED
WL16
0x2000
RW
0x0000
RW
0x000000
R
0x000000
0x0800
R
RW
0x30DX 1
R
0x8001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x0001
RW
0x1000
RW
AIN_BUF 1[1:0]
0x1000
RW
AIN_BUF 2[1:0]
0x1000
RW
CLOCKSEL
ALT_SYNC
IOSTRENGTH
REG_CHECK RESERVED
CRC_EN
REGISTER_CHECK[23:16]
REGISTER_CHECK[15:8]
REGISTER_CHECK[7:0]
DATA[23:0]
OP_EN2_3
MUX_IO
SYNC_EN
ERR_EN
ERR_DAT
IP_EN1
IP_EN0
OP_EN1
OP_EN0
GP_DATA1 GP_DATA0
ID[15:8]
ID[7:0]
SETUP_SEL0
RESERVED
AINPOS0[4:3]
AINNEG0
SETUP_SEL1
RESERVED
AINPOS1[4:3]
AINNEG1
SETUP_SEL2
RESERVED
AINPOS2[4:3]
AINNEG2
SETUP_SEL3
RESERVED
AINPOS3[4:3]
AINNEG3
SETUP_SEL4
RESERVED
AINPOS4[4:3]
AINNEG4
SETUP_SEL5
RESERVED
AINPOS5[4:3]
AINNEG5
SETUP_SEL6
RESERVED
AINPOS6[4:3]
AINNEG6
SETUP_SEL7
RESERVED
AINPOS7[4:3]
AINNEG7
SETUP_SEL8
RESERVED
AINPOS8[4:3]
AINNEG8
SETUP_SEL9
RESERVED
AINPOS9[4:3]
AINNEG9
SETUP_SEL10
RESERVED
AINPOS10[4:3]
AINNEG10
SETUP_SEL11
RESERVED
AINPOS11[4:3]
AINNEG11
SETUP_SEL12
RESERVED
AINPOS12[4:3]
AINNEG12
SETUP_SEL13
RESERVED
AINPOS13[4:3]
AINNEG13
SETUP_SEL14
RESERVED
AINPOS14[4:3]
AINNEG14
SETUP_SEL15
RESERVED
AINPOS15[4:3]
AINNEG15
BI_
REF_BUF 0[1:0]
AIN_BUF 0[1:0]
UNIPOLAR0
REF_SEL0
RESERVED
BI_UNIPOLAR1
REFSEL1
REF_BUF 1[1:0]
BI_UNIPOLAR2
REFSEL2
REF_BUF 2[1:0]
Rev. 0 | Page 45 of 64
RESERVED
RESERVED
AD7173-8
Reg
0x23
0x24
0x25
0x26
0x27
Data Sheet
Name
Bits
SETUPCON3 [15:8]
[7:0]
SETUPCON4 [15:8]
[7:0]
SETUPCON5 [15:8]
[7:0]
SETUPCON6 [15:8]
[7:0]
SETUPCON7 [15:8]
[7:0]
Bit 7
BURNOUT_
EN3
BURNOUT_
EN4
BURNOUT_
EN5
BURNOUT_
EN6
BURNOUT_
EN7
SINC3_MAP0
RESERVED
SINC3_MAP1
RESERVED
SINC3_MAP2
RESERVED
SINC3_MAP3
RESERVED
SINC3_MAP4
RESERVED
SINC3_MAP5
RESERVED
SINC3_MAP6
RESERVED
SINC3_MAP7
RESERVED
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RESERVED
BI_UNIPOLAR3
REF_BUF 3[1:0]
AIN_BUF 3[1:0]
BUFCHOPMAX
REFSEL3
RESERVED
3
RESERVED
BI_UNIPOLAR4
REF_BUF 4[1:0]
AIN_BUF 4[1:0]
BUFCHOPMAX
REFSEL4
RESERVED
4
RESERVED
BI_UNIPOLAR5
REF_BUF 5[1:0]
AIN_BUF 5[1:0]
BUFCHOPMAX
REFSEL5
RESERVED
5
RESERVED
BI_UNIPOLAR6
REF_BUF 6[1:0]
AIN_BUF 6[1:0]
BUFCHOPMAX
REFSEL6
RESERVED
6
RESERVED
BI_UNIPOLAR7
REF_BUF 7[1:0]
AIN_BUF 7[1:0]
BUFCHOPMAX
REFSEL7
RESERVED
7
RESERVED
ENHFILTEN0
ENHFILT0
ORDER0
ODR0
RESERVED
ENHFILTEN1
ENHFILT1
ORDER1
ODR1
RESERVED
ENHFILTEN2
ENHFILT2
ORDER2
ODR2
RESERVED
ENHFILTEN3
ENHFILT3
ORDER3
ODR3
RESERVED
ENHFILTEN4
ENHFILT4
ORDER4
ODR4
RESERVED
ENHFILTEN5
ENHFILT5
ORDER5
ODR5
RESERVED
ENHFILTEN6
ENHFILT6
ORDER6
ODR6
RESERVED
ENHFILTEN7
ENHFILT7
ORDER7
ODR7
OFFSET0[23:0]
OFFSET1[23:0]
OFFSET2[23:0]
OFFSET3[23:0]
OFFSET4[23:0]
OFFSET5[23:0]
OFFSET6[23:0]
OFFSET7[23:0]
GAIN0[23:0]
GAIN1[23:0]
Reset
0x1000
RW
RW
0x1000
RW
0x1000
RW
0x1000
RW
0x1000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x0000
RW
0x800000
0x800000
0x800000
0x800000
0x800000
0x800000
0x800000
0x800000
0x5XXXX0 2
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
0x28
FILTCON0
0x29
FILTCON1
0x2A
FILTCON2
0x2B
FILTCON3
0x2C
FILTCON4
0x2D
FILTCON5
0x2E
FILTCON6
0x2F
FILTCON7
0x30
0x31
0x32
0x33
0x34
0x35
0x36
0x37
0x38
0x39
OFFSET0
OFFSET1
OFFSET2
OFFSET3
OFFSET4
OFFSET5
OFFSET6
OFFSET7
GAIN0
GAIN1
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
0x3A
GAIN2
[23:0]
GAIN2[23:0]
0x5XXXX02
RW
0x3B
GAIN3
[23:0]
GAIN3[23:0]
0x5XXXX02
RW
0x3C
GAIN4
[23:0]
GAIN4[23:0]
0x5XXXX02
RW
0x3D
GAIN5
[23:0]
GAIN5[23:0]
2
RW
0x3E
GAIN6
[23:0]
GAIN6[23:0]
2
0x5XXXX0
RW
0x3F
GAIN7
[23:0]
GAIN7[23:0]
0x5XXXX02
RW
1
2
X = don’t care. The value of X is specific to the ADC.
The value of X varies, depending on the IC that is used.
Rev. 0 | Page 46 of 64
0x5XXXX02
0x5XXXX0
Data Sheet
AD7173-8
REGISTER DETAILS
COMMUNICATIONS REGISTER
Address: 0x00, Reset: 0x00, Name: COMMS
Table 23. Bit Descriptions for COMMS
Bits
7
Bit Name
WEN
6
R/W
Settings
0
1
[5:0]
RA
000000
000001
000010
000011
000100
000110
000111
010000
010001
010010
010011
010100
010101
010110
010111
011000
011001
011010
011011
011100
011101
011110
011111
100000
100001
100010
100011
100100
100101
100110
100111
101000
101001
101010
101011
101100
101101
101110
101111
110000
110001
Description
This bit must be low to begin communications with the ADC.
Reset
0x0
Access
W
This bit determines if the command is a read or write operation.
Write command
Read command
The register address bits determine which register is to be read from or
written to as part of the current communication.
Status register
ADC mode register
Interface mode register
Register checksum register
Data register
GPIO configuration register
ID register
Channel 0 register
Channel 1 register
Channel 2 register
Channel 3 register
Channel 4 register
Channel 5 register
Channel 6 register
Channel 7 register
Channel 8 register
Channel 9 register
Channel 10 register
Channel 11 register
Channel 12 register
Channel 13 register
Channel 14 register
Channel 15 register
Setup Configuration 0 register
Setup Configuration 1 register
Setup Configuration 2 register
Setup Configuration 3 register
Setup Configuration 4 register
Setup Configuration 5 register
Setup Configuration 6 register
Setup Configuration 7 register
Filter Configuration 0 register
Filter Configuration 1 register
Filter Configuration 2 register
Filter Configuration 3 register
Filter Configuration 4 register
Filter Configuration 5 register
Filter Configuration 6 register
Filter Configuration 7 register
Offset 0 register
Offset 1 register
0x0
W
0x00
W
Rev. 0 | Page 47 of 64
AD7173-8
Bits
Bit Name
Data Sheet
Settings
110010
110011
110100
110101
110110
110111
111000
111001
111010
111011
111100
111101
111110
111111
Description
Offset 2 register
Offset 3 register
Offset 4 register
Offset 5 register
Offset 6 register
Offset 7 register
Gain 0 register
Gain 1 register
Gain 2 register
Gain 3 register
Gain 4 register
Gain 5 register
Gain 6 register
Gain 7 register
Reset
Rev. 0 | Page 48 of 64
Access
Data Sheet
AD7173-8
STATUS REGISTER
Address: 0x00, Reset: 0x80, Name: STATUS
The status register is an 8-bit register that contains ADC and serial interface status information. It can optionally be appended to the data
register by setting the DATA_STAT bit in the interface mode register (Bit 6, Register 0x02).
Table 24. Bit Descriptions for STATUS
Bits
7
Bit Name
RDY
Settings
0
1
6
ADC_ERROR
0
1
5
CRC_ERROR
0
1
4
REG_ERROR
0
1
[3:0]
CHANNEL
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Description
The status of RDY is output to the DOUT/RDYpin whenever CS is low and
a register is not being read. This bit goes low when the ADC has written
a new result to the data register. In ADC calibration modes, this bit goes
low when the ADC has written the calibration result. RDY is brought high
automatically by a read of the data register.
New data result available
Awaiting new data result
This bit, by default, indicates if an ADC overrange or underrange has
occurred. The ADC result is clamped to ± full scale if an overrange or
underrange occurs. This bit is updated when the ADC result is written and
is cleared by removing the overrange or underrange condition on the
analog inputs.
No error
Error
This bit indicates if a CRC error has occurred during a register write. For
register reads, the host microcontroller determines if a CRC error has
occurred. This bit is cleared by a read of this register.
No error
CRC error
This bit indicates if the content of one of the internal registers has
changed from the value calculated when the register integrity check was
activated. The check is activated by setting the REG_CHECK bit in the
interface mode register. This bit is cleared by clearing the REG_CHECK bit.
No error
Error
These bits indicate which channel was active for the ADC conversion
whose result is currently in the data register. This may be different from
the channel currently being converted. The bits are a direct mapping from
the Channel x registers; therefore, Channel 0 results in 0x0 and Channel 15
results in 0x1F.
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
Channel 9
Channel 10
Channel 11
Channel 12
Channel 13
Channel 14
Channel 15
Rev. 0 | Page 49 of 64
Reset
0x1
Access
R
0x0
R
0x0
R
0x0
R
0x0
R
AD7173-8
Data Sheet
ADC MODE REGISTER
Address: 0x01, Reset: 0x2000, Name: ADCMODE
The ADC mode register controls the operating mode of the ADC and the master clock selection. A write to the ADC mode register resets
the filter and the RDY bits and starts a new conversion or calibration.
Table 25. Bit Descriptions for ADCMODE
Bits
15
Bit Name
REF_EN
Settings
0
1
14
13
RESERVED
SING_CYC
0
1
[12:11]
[10:8]
RESERVED
DELAY
000
001
010
011
100
101
110
111
7
[6:4]
RESERVED
MODE
000
001
010
011
100
110
111
[3:2]
CLOCKSEL
00
01
10
11
[1:0]
RESERVED
Description
Enables internal reference and outputs a buffered 2.5 V to the REFOUT pin.
Disabled
Enabled
This bit is reserved. Set to 0.
This bit can be used when only a single channel is active to set the ADC to
output only at the settled filter data rate.
Disabled
Enabled
These bits are reserved. Set to 0.
These bits allow a programmable delay to be added after a channel switch
to allow settling of external circuitry before the ADC starts processing its
input.
0 µs
32 µs
128 µs
320 µs
800 µs
1.6 ms
4 ms
8 ms
This bit is reserved. Set to 0.
These bits control the operating mode of the ADC. Details can be found in
the Operating Modes section.
Continuous conversion mode
Single conversion mode
Standby mode
Power-down mode
Internal offset calibration
System offset calibration
System gain calibration
This bit is used to select the ADC clock source. Selecting the internal
oscillator also enables the internal oscillator.
Internal oscillator
Internal oscillator output on XTAL2/CLKIO pin
External clock input on XTAL2/CLKIO pin
External crystal on XTAL1 and XTAL2/CLKIO pins
These bits are reserved. Set to 0.
Rev. 0 | Page 50 of 64
Reset
0x0
Access
RW
0x0
0x1
R
RW
0x0
0x0
R
RW
0x0
0x0
R
RW
0x0
RW
0x0
R
Data Sheet
AD7173-8
INTERFACE MODE REGISTER
Address: 0x02, Reset: 0x0000, Name: IFMODE
The interface mode register configures various serial interface options.
Table 26. Bit Descriptions for IFMODE
Bits
[15:13]
12
Bit Name
RESERVED
ALT_SYNC
Settings
0
1
11
IOSTRENGTH
0
1
[10:9]
8
RESERVED
DOUT_RESET
0
1
7
CONTREAD
0
1
6
DATA_STAT
0
1
5
REG_CHECK
0
1
4
[3:2]
RESERVED
CRC_EN
00
01
10
1
RESERVED
Description
These bits are reserved. Set to 0.
This bit enables a different behavior of the SYNC pin to allow the use
of SYNC as a control for conversions when cycling channels. (For details,
see the description of the SYNC_EN bit in the GPIO Configuration Register.)
Disabled
Enabled
This bit controls the drive strength of the DOUT (DOUT/RDY) pin and the
XTAL2/CLKIO pin. Set this bit to 1 when reading from the serial interface at
high speed with low IOVDD supply and moderate capacitance.
Disabled (default)
Enabled
These bits are reserved. Set to 0.
This bit prevents the DOUT/RDY pin from switching from outputting
DOUT to outputting RDY soon after the last rising edge of SCLK during
a read operation. Instead, the DOUT/RDY pin continues to output the LSB
of the data until CS goes high, providing longer hold times for the SPI
master to sample the LSB of the data. When this bit is set, CS must not be
tied low.
Disabled
Enabled
This bit enables continuous read of the ADC data register. To use continuous
read, configure the ADC in continuous conversion mode. For more details,
see the Operating Modes section.
Disabled
Enabled
This bit enables the status register to be appended to the data register
when read so that channel and status information is transmitted with the
data. This is the only way to ensure that the channel bits read from the
status register correspond to the data in the data register.
Disabled
Enabled
This bit enables a register integrity checker that can be used to monitor
any change in the value of the user registers. To use this feature, configure
all other registers as desired, with this bit cleared. Then write to this register
to set the REG_CHECK bit to 1. If the contents of any of the registers change,
the REG_ERROR bit is set in the status register. To clear the error, set the
REG_CHECK bit to 0. Neither the interface mode register nor the ADC data
or status register is included in the registers that are checked. If a register
must have a new value written, clear this bit first; otherwise, an error is
flagged when the new register contents are written.
Disabled
Enabled
This bit is reserved. Set to 0.
Enables CRC protection of register reads/writes. CRC increases the number of
bytes in a serial interface transfer by one. See the CRC Calculation section
for more details.
Disabled.
XOR checksum enabled for register read transactions. Register writes still
use CRC with these bits set.
CRC checksum enabled for read and write transactions.
This bit is reserved. Set to 0.
Rev. 0 | Page 51 of 64
Reset
0x0
0x0
Access
R
RW
0x0
RW
0x0
0x0
R
RW
0x0
RW
0x0
RW
0x0
RW
0x0
0x00
R
RW
0x0
R
AD7173-8
Bits
0
Bit Name
WL16
Data Sheet
Settings
0
1
Description
Changes the ADC data register to 16 bits. The ADC is not reset by a write
to the interface mode register; therefore, the ADC result isnot rounded to
the correct word length immediately after writing to these bits. The first
new ADC result is correct.
24-bit data
16-bit data
Reset
0x0
Access
RW
REGISTER CHECK
Address: 0x03, Reset: 0x000000, Name: REGCHECK
The register check register is a 24-bit checksum calculated by XOR'ing the contents of the user registers and some nonaccessible registers.
The REG_CHECK bit in the interface mode register must be set for this to operate; otherwise, the register reads 0.
Table 27. Bit Descriptions for REGCHECK
Bits
[23:0]
Bit Name
REGISTER_CHECK
Settings
Description
This register contains the 24-bit checksum of user registers when the
REG_CHECK bit is set in the interface mode register.
Reset
0x000000
Access
R
DATA REGISTER
Address: 0x04, Reset: 0x000000, Name: DATA
The data register contains the ADC conversion result. The encoding is offset binary; however, it can be changed to unipolar by the
BI_UNIPOLAR bit in the setup configuration register. Reading the data register brings the RDY bit and pin high if they are low. The
ADC result can be read multiple times; however, because RDY has been brought high, it is not possible to know if another ADC result is
imminent. The ADC does not write a new result into the data register if the register is currently being read.
Table 28. Bit Descriptions for DATA
Bits
[23:0]
Bit Name
DATA
Settings
Description
This register contains the ADC conversion result. If the DATA_STAT bit is
set in the interface mode register, the status register is appended to this
register when read, making this a 32-bit register. If WL16 is set in the
interface mode register, this register is set to a length of 16 bits.
Rev. 0 | Page 52 of 64
Reset
0x000000
Access
R
Data Sheet
AD7173-8
GPIO CONFIGURATION REGISTER
Address: 0x06, Reset: 0x0800, Name: GPIOCON
The GPIO configuration register controls the general-purpose I/O pins of the ADC.
Table 29. Bit Descriptions for GPIOCON
Bits
15
14
Bit Name
RESERVED
PDSW
13
OP_EN2_3
12
MUX_IO
11
SYNC_EN
Settings
0
1
[10:9]
ERR_EN
00
01
10
11
8
ERR_DAT
7
6
5
GP_DATA3
GP_DATA2
IP_EN1
0
1
Description
This bit is reserved. Set to 0.
This bit enables/disables the power-down switch function. Setting the bit
allows the pin to sink current. This function can be used for bridge sensor
applications where the switch controls the power-up/power-down of the
bridge.
This bit enables the GPO2 and GPO3 pins. Outputs are referenced between
AVDD1 and AVSS.
This bit allows the ADC to control an external multiplexer, using GPIO0/GPIO1/
GPO2/GPO3 in sync with the internal channel sequencing. The analog input
pins used for a channel can still be selected on a per channel basis. Therefore,
it is possible to have a 16-channel multiplexer in front of each analog input
pair (AIN0/AIN1 to AIN14/AIN15), giving a total of 128 differential channels.
However, only 16 channels at a time can be automatically sequenced. Following
the sequence of 16 channels, the user changes the analog input to the next pair
of input channels, and it sequences through the next 16 channels.
There is a delay function that allows extra time for the analog input to settle, in
conjunction with any switching an external multiplexer (see the delay bits in
the ADC Mode Register).
This bit enables the SYNC pin as a sync input. When set low, the SYNC pin
holds the ADC and filter in reset until SYNC goes high. An alternative
operation of the SYNC pin is available when the ALT_SYNC bit in the
interface mode register is set. This mode works only when multiple
channels are enabled. In such cases, a low on the SYNC pin does not
immediately reset the filter/modulator. Instead, if the SYNC pin is low when
the channel is due to be switched, the modulator and filter are prevented
from starting a new conversion. Bringing SYNC high begins the next
conversion. This alternative sync mode allows SYNC to be used while cycling
through channels.
Disabled
Enabled
These bits enable the ERROR pin as an error input/output.
Disabled
ERROR is an error input. The (inverted) readback state is OR'ed with other
error sources and is available in the ADC_ERROR bit in the status register.
The ERROR pin state can also be read from the ERR_DAT bit in this register.
ERROR is an open-drain error output. The status register error bits are
OR'ed, inverted, and mapped to the ERROR pin. ERROR pins of multiple
devices can be wired together to a common pull-up resistor so that an error
on any device can be observed.
ERROR is a general-purpose output. The status of the pin is controlled by
the ERR_DAT bit in this register. This is referenced between IOVDD and
DGND, as opposed to the AVDD1 and AVSS levels used by the generalpurpose I/O pins. It has an active pull-up in this case.
This bit determines the logic level at the ERROR pin if the pin is enabled as a
general-purpose output. It reflects the readback status of the pin if the pin
is enabled as an input.
This bit is the write data for GPO3.
This bit is the write data for GPO2.
This bit turns GPIO1 into an input. Input should equal AVDD1 or AVSS.
Disabled
Enabled
Rev. 0 | Page 53 of 64
Reset
0x0
0x0
Access
R
RW
0x0
RW
0x0
RW
0x1
RW
0x0
RW
0x0
RW
0x0
0x0
0x0
W
W
RW
AD7173-8
Bits
4
Bit Name
IP_EN0
Data Sheet
Settings
Description
This bit turns GPIO0 into an input. Input should equal AVDD1 or AVSS.
Disabled
Enabled
This bit turns GPIO1 into an output. Outputs are referenced between
AVDD1 and AVSS.
Disabled
Enabled
This bit turns GPIO0 into an output. Outputs are referenced between
AVDD1 and AVSS.
Disabled
Enabled
This bit is the readback or write data for GPIO1.
This bit is the readback or write data for GPIO0.
0
1
3
OP_EN1
0
1
2
OP_EN0
0
1
1
0
GP_DATA1
GP_DATA0
Reset
0x0
Access
RW
0x0
RW
0x0
RW
0x0
0x0
RW
RW
Reset
0x30DX 1
Access
R
ID REGISTER
Address: 0x07, Reset: 0x30DX, Name: ID
The ID register returns a 16-bit ID. For the AD7173-8, this is 0x30DX.
Table 30. Bit Descriptions for ID
Bits
[15:0]
Bit Name
ID
Settings
Description
The ID register returns a 16-bit ID code that is specific to the ADC.
AD7173-8
0x30DX
1
X = don’t care.
CHANNEL REGISTER 0
Address: 0x10, Reset: 0x8001, Name: CH0
The channel registers are 16-bit registers that are used to select which channels are currently active, which inputs are selected for each
channel, and which setup should be used to configure the ADC for that channel.
Table 31. Bit Descriptions for CH0
Bits
15
Bit Name
CH_EN0
Settings
0
1
[14:12]
SETUP_SEL0
000
001
010
011
100
101
110
111
[11:10]
RESERVED
Description
This bit enables Channel 0. If more than one channel is enabled, the ADC
automatically sequences between them.
Disabled
Enabled (default)
These bits identify which of the eight setups are used to configure the
ADC for this channel.
A setup comprises a set of four registers: the setup configuration register, the
filter configuration register, the offset register, and the gain register.
All channels can use the same setup, in which case the same 3-bit value
is written to these bits on all active channels; alternatively, up to eight
channels can be configured differently.
Setup 0
Setup 1
Setup 2
Setup 3
Setup 4
Setup 5
Setup 6
Setup 7
These bits are reserved. Set to 0.
Rev. 0 | Page 54 of 64
Reset
0x1
Access
RW
0x0
RW
0x0
R
Data Sheet
Bits
[9:5]
Bit Name
AINPOS0
AD7173-8
Settings
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10101
10110
[4:0]
AINNEG0
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10101
10110
Description
These bits select which of the analog inputs is connected to the positive
input of the ADC for this channel. TEMP SENSOR ± is an internal temperature sensor.
AIN0 (default)
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
AIN16
TEMP SENSOR +
TEMP SENSOR −
REF+
REF−
These bits select which of the analog inputs is connected to the negative
input of the ADC for this channel.
AIN0
AIN1(default)
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
AIN16
TEMP SENSOR +
TEMP SENSOR −
REF+
REF−
Rev. 0 | Page 55 of 64
Reset
0x0
Access
RW
0x1
RW
AD7173-8
Data Sheet
CHANNEL REGISTER 1 TO CHANNEL REGISTER 15
Address Range: 0x11 to 0x1F, Reset: 0x0001, Name: CH1 to CH15
Subsequent channel registers, CH1 to CH15, use the same structure as the CH0 register. They are disabled by default (MSB = 0). Each
channel created can be referred to one of eight setups. The sequencer progresses through each of the enabled channels in order.
Table 32 shows the summary of these registers, their addresses, and their reset values.
Table 32. Summary of CH1 to CH15
Reg
0x11
Name
CH1
0x12
CH2
0x13
CH3
0x14
CH4
0x15
CH5
0x16
CH6
0x17
CH7
0x18
CH8
0x19
CH9
0x1A
CH10
0x1B
CH11
0x1C
CH12
0x1D
CH13
0x1E
CH14
0x1F
CH15
Bits
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
Bit 7
CH_EN1
CH_EN2
CH_EN3
CH_EN4
CH_EN5
CH_EN6
CH_EN7
CH_EN8
CH_EN9
CH_EN10
CH_EN11
CH_EN12
CH_EN13
CH_EN14
CH_EN15
Bit 6
Bit 5
Bit 4
SETUP_SEL1
AINPOS1[2:0]
SETUP_SEL2
AINPOS2[2:0]
SETUP_SEL3
AINPOS3[2:0]
SETUP_SEL4
AINPOS4[2:0]
SETUP_SEL5
AINPOS5[2:0]
SETUP_SEL6
AINPOS6[2:0]
SETUP_SEL7
AINPOS7[2:0]
SETUP_SEL8
AINPOS8[2:0]
SETUP_SEL9
AINPOS9[2:0]
SETUP_SEL10
AINPOS10[2:0]
SETUP_SEL11
AINPOS11[2:0]
SETUP_SEL12
AINPOS12[2:0]
SETUP_SEL13
AINPOS13[2:0]
SETUP_SEL14
AINPOS14[2:0]
SETUP_SEL15
AINPOS15[2:0]
Bit 3
Rev. 0 | Page 56 of 64
Bit 2
Bit 1
RESERVED
AINNEG1
RESERVED
AINNEG2
RESERVED
AINNEG3
RESERVED
AINNEG4
RESERVED
AINNEG5
RESERVED
AINNEG6
RESERVED
AINNEG7
RESERVED
AINNEG8
RESERVED
AINNEG9
RESERVED
AINNEG10
RESERVED
AINNEG11
RESERVED
AINNEG12
RESERVED
AINNEG13
RESERVED
AINNEG14
RESERVED
AINNEG15
Bit 0
AINPOS1[4:3]
Reset
0x0001
RW
RW
AINPOS2[4:3]
0x0001
RW
AINPOS3[4:3]
0x0001
RW
AINPOS4[4:3]
0x0001
RW
AINPOS5[4:3]
0x0001
RW
AINPOS6[4:3]
0x0001
RW
AINPOS7[4:3]
0x0001
RW
AINPOS8[4:3]
0x0001
RW
AINPOS9[4:3]
0x0001
RW
AINPOS10[4:3]
0x0001
RW
AINPOS11[4:3]
0x0001
RW
AINPOS12[4:3]
0x0001
RW
AINPOS13[4:3]
0x0001
RW
AINPOS14[4:3]
0x0001
RW
AINPOS15[4:3]
0x0001
RW
Data Sheet
AD7173-8
SETUP CONFIGURATION REGISTER 0
Address: 0x20, Reset: 0x1000, Name: SETUPCON0
The setup configuration registers are 16-bit registers that configure the reference selection, input buffers, burnout currents, and output
coding of the ADC.
Table 33. Bit Descriptions for SETUPCON0
Bits
[15:13]
12
Bit Name
RESERVED
BI_UNIPOLAR0
Settings
0
1
[11:10]
REF_BUF_0[1:0]
00
11
[9:8]
AIN_BUF_0[1:0]
00
11
7
BURNOUT_EN0
6
BUFCHOPMAX0
[5:4]
REF_SEL0
00
01
10
11
[3:0]
RESERVED
Description
These bits are reserved. Set to 0.
This bit sets the output coding of the ADC for Setup 0.
Unipolar coded output
Offset binary coded output
Reference input buffer enable. These bits turn on the buffers of the
positive and negative reference inputs. This offers a high impedance input
for an external reference source and isolates it from the switch capacitor
reference sampling input of the ADC. Use both reference buffers together.
Reference input buffers disabled
Reference input buffers enabled
Analog input buffer enable. These bits turn on the buffers of the positive
and negative analog inputs. This offers a high impedance input to the
device and isolates the sensor/signal for measurement from the switch
capacitor sampling input of the ADC. Use both analog input buffers
together.
Analog input buffers disabled
Analog input buffers enabled
This bit enables a 10 µA current source on the positive analog input
selected and a 10 µA current sink on the negative analog input selected.
The burnout currents are useful in diagnosis of an open wire, whereby the
ADC result goes to full scale. Enabling the BURNOUT currents during
measurement results in an offset voltage on the ADC reading of
approximately 1 µV. This means the strategy for diagnosing an open wire
operates best by turning on the BURNOUT currents at intervals, before or
after precision measurements.
This bit enables the maximum buffer chop frequency, increasing AIN
input current and reducing buffer noise.
These bits allow selection of the reference source for ADC conversion on
Setup 0.
External reference supplied to REF+ and REF− pins
External Reference 2 supplied to AIN1/REF2+ and AIN0/REF2− pins
Internal 2.5 V reference; this reference must also be enabled in the ADC mode
register
AVDD1 – AVSS; this setting can be used to as a diagnostic to validate other
reference values
These bits are reserved. Set to 0.
Rev. 0 | Page 57 of 64
Reset
0x0
0x1
Access
R
RW
0x0
RW
0x0
RW
0x0
RW
0x0
RW
0x0
RW
0x0
R
AD7173-8
Data Sheet
SETUP CONFIGURATION REGISTER 1 TO SETUP CONFIGURATION REGISTER 7
Address: 0x21 to 0x27, Reset: 0x1000, Name: SETUPCON1 to SETUPCON7
The remaining seven setup configuration registers share the same 16-bit register layout as SETUPCON0. They configure the reference
selection, input buffers, burnout currents, and output coding of the ADC.
Table 34. Summary of SETUPCON1 to SETUPCON7
Reg
0x21
0x22
0x23
0x24
0x25
0x26
0x27
Name
Bits
Bit 7
SETUPCON1 [15:8]
[7:0] BURNOUT_
EN1
SETUPCON2 [15:8]
[7:0] BURNOUT_
EN2
SETUPCON3 [15:8]
[7:0] BURNOUT_
EN3
SETUPCON4 [15:8]
[7:0] BURNOUT_
EN4
SETUPCON5 [15:8]
[7:0] BURNOUT_
EN5
SETUPCON6 [15:8]
[7:0] BURNOUT_
EN6
SETUPCON7 [15:8]
[7:0] BURNOUT_
EN7
Bit 6
Bit 5
RESERVED
BUFCHOPMAX1
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
BI_UNIPOLAR1
REF_BUF 1[1:0]
AIN_BUF 1[1:0]
REFSEL1
RESERVED
Reset
0x1000
RW
RW
RESERVED
BUFCHOPMAX2
BI_UNIPOLAR2
REFSEL2
REF_BUF 2[1:0]
AIN_BUF 2[1:0]
0x1000
RW
RESERVED
BUFCHOPMAX3
BI_UNIPOLAR3
REFSEL3
REF_BUF 3[1:0]
AIN_BUF 3[1:0]
0x1000
RW
RESERVED
BUFCHOPMAX4
BI_UNIPOLAR4
REFSEL4
REF_BUF 4[1:0]
AIN_BUF 4[1:0]
0x1000
RW
RESERVED
BUFCHOPMAX5
BI_UNIPOLAR5
REFSEL5
REF_BUF 5[1:0]
AIN_BUF 5[1:0]
0x1000
RW
RESERVED
BUFCHOPMAX6
BI_UNIPOLAR6
REFSEL6
REF_BUF 6[1:0]
AIN_BUF 6[1:0]
0x1000
RW
RESERVED
BUFCHOPMAX7
BI_UNIPOLAR7
REFSEL7
REF_BUF 7[1:0]
AIN_BUF 7[1:0]
0x1000
RW
Rev. 0 | Page 58 of 64
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
Data Sheet
AD7173-8
FILTER CONFIGURATION REGISTER 0
Address: 0x28, Reset: 0x0000, Name: FILTCON0
The filter configuration registers are 16-bit registers that configure the ADC data rate and filter options. Writing to any of these registers
resets any active ADC conversion and restarts converting at the first channel in the sequence.
Table 35. Bit Descriptions for FILTCON0
Bits
15
Bit Name
SINC3_MAP0
[14:12]
11
RESERVED
ENHFILTEN0
Settings
0
1
[10:8]
ENHFILT0
010
011
101
110
7
[6:5]
RESERVED
ORDER0
00
11
[4:0]
ODR0
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10011
10100
10101
10110
Description
If this bit is set, the mapping of the filter configuration register changes to
directly program the decimation rate of the sinc3 filter for Setup 0. All
other options are eliminated. This allows fine tuning of the output data
rate and filter notch for rejection of specific frequencies. The data rate
when on a single channel, with single cycle settling disabled, equals
FMOD/(32 × FILTCON0[14:0]).
These bits are reserved. Set to 0.
This bit enables various post filters for enhanced 50 Hz/60 Hz rejection for
Setup 0. For this setting to function, the ORDERx bits must also be set to
00 to select the sinc5 + sinc1 filter.
Disabled
Enabled
These bits select between various post filters for enhanced 50 Hz/60 Hz
rejection for Setup 0.
27.27 SPS, 47 dB rejection, 36.67 ms settling
25 SPS, 62 dB rejection, 40 ms settling
20 SPS, 86 dB rejection, 50 ms settling
16.67 SPS, 92 dB rejection, 60 ms settling
This bit is reserved. Set to 0.
These bits control the order of the digital filter that processes the
modulator data for Setup 0.
Sinc5 + sinc1 (default)
Sinc3
These bits control the output data rate of the ADC and, therefore, the
settling time and noise for Setup 0.
31,250 SPS
31,250 SPS
31,250 SPS
31,250 SPS
31,250 SPS
31,250 SPS
15,625 SPS
10,417 SPS
5208 SPS
2597 SPS (2604 SPS for sinc3)
1007 SPS (1008 SPS for sinc3)
503.8 SPS (504 SPS for sinc3)
381 SPS (400.6 SPS for sinc3)
200.3 SPS
100.5 SPS
59.52 SPS (59.98 SPS for sinc3)
49.68 SPS (50 SPS for sinc3)
20.01 SPS
16.63 SPS (16.67 SPS for sinc3)
10 SPS
5 SPS
2.5 SPS
1.25 SPS
Rev. 0 | Page 59 of 64
Reset
0x0
Access
RW
0x0
0x0
R
RW
0x0
RW
0x0
0x0
R
RW
0x0
RW
AD7173-8
Data Sheet
FILTER CONFIGURATION REGISTER 1 TO FILTER CONFIGURATION REGISTER 7
Address Range: 0x29 to 0x2F, Reset: 0x0000, Name: FILTCON1 to FILTCON7
The remaining seven filter configuration registers share the same 16-bit register layout as FILTCON0. They configure the ADC data rate
and filter options and map as per their number. Writing to any of these registers resets any active ADC conversion and restarts converting
at the first channel in the sequence.
Table 36. Summary of FILTCON1 to FILTCON7
Reg
0x29
Name
FILTCON1
0x2A
FILTCON2
0x2B
0x2C
0x2D
0x2E
0x2F
FILTCON3
FILTCON4
FILTCON5
FILTCON6
FILTCON7
Bits
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
Bit 7
SINC3_MAP1
RESERVED
SINC3_MAP2
RESERVED
SINC3_MAP3
RESERVED
SINC3_MAP4
RESERVED
SINC3_MAP5
RESERVED
SINC3_MAP6
RESERVED
SINC3_MAP7
RESERVED
Bit 6
Bit 5
RESERVED
ORDER1
RESERVED
ORDER2
RESERVED
ORDER3
RESERVED
ORDER4
RESERVED
ORDER5
RESERVED
ORDER6
RESERVED
ORDER7
Bit 4
Bit 3
ENHFILTEN1
Bit 2
Bit 1
Bit 0
ENHFILT1
Reset
0x0000
RW
RW
ENHFILT2
0x0000
RW
ENHFILT3
0x0000
RW
ENHFILT4
0x0000
RW
ENHFILT5
0x0000
RW
ENHFILT6
0x0000
RW
ENHFILT7
0x0000
RW
ODR1
ENHFILTEN2
ODR2
ENHFILTEN3
ODR3
ENHFILTEN4
ODR4
ENHFILTEN5
ODR5
ENHFILTEN6
ODR6
ENHFILTEN7
Rev. 0 | Page 60 of 64
ODR7
Data Sheet
AD7173-8
OFFSET REGISTER 0
Address: 0x30, Reset: 0x800000, Name: OFFSET0
The offset (zero-scale) registers are 24-bit registers that can be used to compensate for any offset error in the ADC or in the system.
Table 37. Bit Descriptions for OFFSET0
Bits
[23:0]
Bit Name
OFFSET0
Settings
Description
Offset calibration coefficient for Setup 0.
Reset
0x800000
Access
RW
OFFSET REGISTER 1 TO OFFSET REGISTER 7
Address Range: 0x31to 0x37, Reset: 0x800000, Name: OFFSET1 to OFFSET7
The offset (zero-scale) registers, OFFSET1 to OFFSET7, share the same structure (24-bit) as OFFSET0. They can be used individually to
compensate for any offset error in the ADC or in the system.
Table 38. Summary of OFFSET1 to OFFSET7
Reg
0x31
0x32
0x33
0x34
0x35
0x36
0x37
Name
OFFSET1
OFFSET2
OFFSET3
OFFSET4
OFFSET5
OFFSET6
OFFSET7
Bits
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
Bit[23:0]
OFFSET1[23:0]
OFFSET2[23:0]
OFFSET3[23:0]
OFFSET4[23:0]
OFFSET5[23:0]
OFFSET6[23:0]
OFFSET7[23:0]
Reset
0x800000
0x800000
0x800000
0x800000
0x800000
0x800000
0x800000
RW
RW
RW
RW
RW
RW
RW
RW
GAIN REGISTER 0
Address: 0x38, Reset: 0x5XXXX0, Name: GAIN0
The gain (full-scale) registers are 24-bit registers that can be used to compensate for any gain error in the ADC or in the system.
Table 39. Bit Descriptions for GAIN0
Bits
[23:0]
1
Bit Name
GAIN0
Settings
Description
Gain calibration coefficient for Setup 0.
Reset 1
0x5XXXX0
Access
RW
The value of X varies, depending on the IC that is used.
GAIN REGISTER 1 TO GAIN REGISTER 7
Address Range: 0x39 to 0x3F, Reset: 0x5XXXX0, Name: GAIN1 to GAIN7
The gain (full-scale) registers for GAIN1 to GAIN7 share the same 24-bit structure as that shown by GAIN0 register. They can be used to
compensate for any gain error in the ADC or in the system and are assigned as per their number to a given setup.
Table 40. Summary of GAIN1 to GAIN7
Reg
0x39
0x3A
0x3B
0x3C
0x3D
0x3E
0x3F
1
Name
GAIN1
GAIN2
GAIN3
GAIN4
GAIN5
GAIN6
GAIN7
Bits
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
[23:0]
Bit[23:0]
GAIN1[23:0]
GAIN2[23:0]
GAIN3[[23:0]
GAIN4[23:0]
GAIN5[23:0]
GAIN6[23:0]
GAIN7[23:0]
The value of X varies, depending on the IC that is used.
Rev. 0 | Page 61 of 64
Reset 1
0x5XXXX0
0x5XXXX0
0x5XXXX0
0x5XXXX0
0x5XXXX0
0x5XXXX0
0x5XXXX0
RW
RW
RW
RW
RW
RW
RW
RW
AD7173-8
Data Sheet
OUTLINE DIMENSIONS
0.30
0.25
0.18
31
40
30
0.50
BSC
1
TOP VIEW
0.80
0.75
0.70
10
11
20
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.20 REF
SEATING
PLANE
4.05
3.90 SQ
3.75
EXPOSED
PAD
21
0.45
0.40
0.35
PIN 1
INDICATOR
BOTTOM VIEW
0.25 MIN
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
COMPLIANT TO JEDEC STANDARDS MO-220-WJJD.
05-06-2011-A
PIN 1
INDICATOR
6.10
6.00 SQ
5.90
Figure 75. 40-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
6 mm × 6 mm Body, Very Very Thin Quad
(CP-40-14)
Dimensions shown in millimeters
ORDERING GUIDE
Models 1
AD7173-8BCPZ
AD7173-8BCPZ-RL
EVAL-AD7173-8SDZ
EVAL-SDP-CB1Z
1
Temperature Range
−40°C to +105°C
−40°C to +105°C
Package Description
40-Lead LFCSP_WQ
40-Lead LFCSP_WQ
Evaluation Board
Evaluation Controller Board
Z = RoHS Compliant Part.
Rev. 0 | Page 62 of 64
Package Option
CP-40-14
CP-40-14
Data Sheet
AD7173-8
NOTES
Rev. 0 | Page 63 of 64
AD7173-8
Data Sheet
NOTES
©2013 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D11773-0-10/13(0)
Rev. 0 | Page 64 of 64