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PDF AD7172-2 Data sheet ( Hoja de datos )
| Número de pieza | AD7172-2 | |
| Descripción | Sigma-Delta ADC | |
| Fabricantes | Analog Devices | |
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Data Sheet
Low Power, 24-Bit, 31.25 kSPS, Sigma-Delta
ADC with True Rail-to-Rail Buffers
AD7172-2
FEATURES
GENERAL DESCRIPTION
Fast and flexible output rate: 1.25 SPS to 31.25 kSPS
Channel scan data rate of 6.21 kSPS/channel (161 µs settling)
Performance specifications
17.2 noise free bits at 31.25 kSPS
24 noise free bits at 5 SPS
INL: ±2 ppm of FSR
85 dB rejection of 50 Hz and 60 Hz with 50 ms settling
User configurable input channels
2 fully differential channels or 4 single-ended channels
Crosspoint multiplexer
On-chip 2.5 V reference (±2 ppm/°C drift)
True rail-to-rail analog and reference input buffers
Internal or external clock
Power supply
AVDD1 = 3.0 V to 5.5 V, AVDD2 = IOVDD = 2 V to 5.5 V
Split supply with AVDD1 and AVSS at ±2.5 V or ±1.65 V
ADC current: 1.5 mA
Temperature range: −40°C to +105°C
3- or 4-wire serial digital interface (Schmitt trigger on SCLK)
Serial port interface (SPI), QSPI-, MICROWIRE-, and DSP-
compatible
APPLICATIONS
Process control: PLC/DCS modules
Temperature and pressure measurement
Medical and scientific multichannel instrumentation
Chromatography
The AD7172-2 is an intelligent, low noise, low power, multiplexed,
Σ-Δ analog-to-digital converter (ADC) with 2- or 4-channel
(fully differential/single-ended) inputs for low bandwidth
signals. The AD7172-2 has a maximum channel scan rate of
6.21 kSPS (161 µs) for fully settled data. The output data rates
range from 1.25 SPS to 31.25 kSPS.
The AD7172-2 integrates key analog and digital signal condition-
ing blocks to allow users to configure an individual setup for each
analog input channel in use via the SPI. Integrated true rail-to-rail
buffers on the analog inputs and external reference inputs provide
easy to drive high impedance inputs. The precision 2.5 V low drift
(2 ppm/°C) band gap internal reference (with an output reference
buffer) adds embedded functionality to reduce the external
component count.
The digital filter allows simultaneous 50 Hz and 60 Hz rejection
at a 27.27 SPS output data rate. The user can switch between
different filter options according to the demands of each channel in
the application, with further digital processing functions such as
offset and gain calibration registers, which are also configurable on
a per channel basis. General-purpose inputs/outputs (GPIOs)
control external multiplexers synchronous to the ADC conversion
timing.
The specified operating temperature range is −40°C to +105°C.
The AD7172-2 is in a 24-lead TSSOP package.
Note that, throughout this data sheet, the dual function pin
names are referenced by the relevant function only.
FUNCTIONAL BLOCK DIAGRAM
AVDD1 AVDD2 REGCAPA
REF– REF+ REFOUT
IOVDD REGCAPD
CROSSPOINT
MULTIPLEXER
1.8V
LDO
AIN0
AIN1
AIN2
AVDD
AVDD1
AVSS
RAIL-TO-RAIL
REFERENCE
INPUT BUFFERS
Σ-Δ ADC
BUFFERED
PRECISION
REFERENCE
INT
REF
DIGITAL
FILTER
1.8V
LDO
SERIAL
INTERFACE
AND CONTROL
AIN3
AIN4
RAIL-TO-RAIL
ANALOG INPUT
AVSS
BUFFERS
TEMPERATURE
SENSOR
GPIO AND
MUX
I/O CONTROL
XTAL AND INTERNAL
CLOCK OSCILLATOR
CIRCUITRY
AD7172-2
CS
SCLK
DIN
DOUT/RDY
SYNC/ERROR
AVSS
GPIO0 GPIO1
XTAL1 XTAL2/CLKIO
Figure 1.
DGND
Rev. A
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2014–2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD7172-2
Data Sheet
SPECIFICATIONS
AVDD1 = 3.0 V to 5.5 V, AVDD2 = IOVDD = 2 V to 5.5 V, AVSS = DGND = 0 V, REF+ = 2.5 V, REF− = AVSS,
MCLK = internal master clock = 2 MHz, TA = TMIN to TMAX (−40°C to +105°C), unless otherwise noted.
Table 1.
Parameter
ADC SPEED AND PERFORMANCE
Output Data Rate (ODR)
No Missing Codes1
Resolution
Noise
ACCURACY
Integral Nonlinearity (INL)
Offset Error2
Offset Drift
Gain Error2
Gain Drift
REJECTION
Power Supply Rejection
Common-Mode Rejection
At DC
At 50 Hz, 60 Hz1
Normal Mode Rejection1
ANALOG INPUTS
Differential Input Range
Absolute Voltage Limits1
Input Buffers Disabled
Input Buffers Enabled
Analog Input Current
Input Buffers Disabled
Input Current
Input Current Drift
Input Buffers Enabled
Input Current
Input Current Drift
Crosstalk
INTERNAL REFERENCE
Output Voltage
Initial Accuracy3
Temperature Coefficient1
0°C to 105°C
−40°C to +105°C
Reference Load Current, ILOAD
Power Supply Rejection
Load Regulation
Voltage Noise
Voltage Noise Density
Turn On Settling Time
Short-Circuit Current, ISC
Test Conditions/Comments
Excluding sinc3 filter ≥ 15 kSPS
See Table 6 and Table 7
See Table 6 and Table 7
Internal short
Internal short
AVDD1 = 5 V
AVDD1, AVDD2, VIN = 1 V
VIN = 0.1 V
20 Hz output data rate (postfilter), 50 Hz ±
1 Hz and 60 Hz ± 1 Hz
50 Hz ± 1 Hz and 60 Hz ± 1 Hz
Internal clock, 20 SPS ODR (postfilter)
External clock, 20 SPS ODR (postfilter)
VREF = (REF+) − (REF−)
External clock
Internal clock (±2.5% clock)
1 kHz input
100 nF external capacitor to AVSS
REFOUT, with respect to AVSS
REFOUT, TA = 25°C
AVDD1, AVDD2 (line regulation)
∆VOUT/∆ILOAD
eN, 0.1 Hz to 10 Hz, 2.5 V reference
eN, 1 kHz, 2.5 V reference
100 nF REFOUT capacitor
Min Typ
1.25
24
±2
±40
±65
±5
±0.2
98
95
120
71 90
85 90
±VREF
AVSS − 0.05
AVSS
−0.12
−10
±6
±75
±0.5
±5
±0.1
−120
2.5
±2
±3
90
50
4.5
215
200
25
Max
31,250
±5
±45
±0.5
AVDD1 + 0.05
AVDD1
+0.12
±5
±10
+10
Unit
SPS
Bits
ppm of FSR
µV
nV/°C
ppm of FSR
ppm/°C
dB
dB
dB
dB
dB
V
V
V
µA/V
pA/V/°C
nA/V/°C
nA
nA/°C
dB
V
% of V
ppm/°C
ppm/°C
mA
dB
ppm/mA
µV rms
nV/√Hz
µs
mA
Rev. A | Page 4 of 60
5 Page 
AD7172-2
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AIN4 1
24 AIN3
REF– 2
23 AIN2
REF+ 3
22 AIN1
REFOUT 4
21 AIN0
REGCAPA 5
AVSS 6
AVDD1 7
AD7172-2
TOP VIEW
(Not to Scale)
20 GPIO1
19 GPIO0
18 REGCAPD
AVDD2 8
17 DGND
XTAL1 9
16 IOVDD
XTAL2/CLKIO 10
15 SYNC/ERROR
DOUT/RDY 11
14 CS
DIN 12
13 SCLK
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin No. Mnemonic Type1 Description
1 AIN4
AI Analog Input 4. Analog Input 4 is selectable through the crosspoint multiplexer.
2 REF−
AI Reference Input Negative Terminal. REF− can span from AVSS to AVDD1 − 1 V.
3 REF+
AI Reference Input Positive Terminal. An external reference can be applied between REF+ and REF−. REF+
can span from AVSS + 1 V to AVDD1.The device functions with a reference magnitude from 1 V to
AVDD1.
4
REFOUT
AO Buffered Output of Internal Reference. The output is 2.5 V with respect to AVSS.
5
REGCAPA
AO Analog LDO Regulator Output. Decouple this pin to AVSS using a 1 µF and a 0.1 µF capacitor.
6 AVSS
P Negative Analog Supply. This supply ranges from −2.75 V to 0 V and is nominally set to 0 V.
7 AVDD1 P Analog Supply Voltage 1. This voltage is 3.3 V or 5 V ± 10% with respect to AVSS.
8 AVDD2 P Analog Supply Voltage 2. This voltage ranges from 2 V to 5.5 V with respect to AVSS.
9 XTAL1
AI Input 1 for Crystal.
10
XTAL2/CLKIO AI/
Input 2 for Crystal/Clock Input or Output. Based on the CLOCKSEL bits in the ADCMODE register. The
DI/O following four options are available for selecting the MCLK source:
Internal oscillator: no output.
Internal oscillator: output to XTAL2/CLKIO. Operates at IOVDD logic level.
External clock: input to XTAL2/CLKIO. Input must be at IOVDD logic level.
External crystal: connected between XTAL1 and XTAL2/CLKIO.
11
DOUT/RDY DO
Serial Data Output/Data Ready Output. DOUT/RDY is a dual purpose pin. This pin 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 three-stated. When CS is low, 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.
12 DIN
DI 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.
13 SCLK
DI Serial Clock Input. This serial clock input is for data transfers to and from the ADC. The SCLK has a
Schmitt triggered input, making the interface suitable for opto-isolated applications.
14 CS
DI Chip Select Input. This is an active low logic input selects the ADC. CS can 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 the SCLK, DIN, and DOUT pins interfacing with the device. When CS is high, the
DOUT/RDY output is three-stated.
Rev. A | Page 10 of 60
11 Page | ||
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