Pin-Programmable, Ultralow Noise, 24-Bit,
Sigma-Delta ADC for Bridge Sensors
AD7191
FEATURES
GENERAL DESCRIPTION
Pin-programmable output rate
Output data rate: 10 Hz, 50 Hz, 60 Hz, 120 Hz
Pin-programmable PGA
The AD7191 is a low noise, complete analog front end for high
precision measurement applications. It contains a low noise,
24-bit sigma-delta (Σ-Δ) ADC. The on-chip low noise gain
stage means that signals of small amplitude can be interfaced
directly to the ADC. It contains two differential analog inputs.
The part also includes a temperature sensor that can be used for
temperature compensation.
Gain: 1, 8, 64, 128
Pin-programmable power-down and reset
RMS noise: 15 nV @ 10 Hz (gain = 128)
Up to 21.5 noise free bits (gain = 1)
Internal or external clock
For ease-of-use, all the features of the AD7191 are controlled by
dedicated pins. The on-chip PGA has a gain of 1, 8, 64, or 128,
supporting a full-scale differential input of ±± ꢀ, ±62± mꢀ,
±78 mꢀ, or ±ꢁ9 mꢀ. The output data rate can be programmed
to 10 Hz, ±0 Hz, 60 Hz, or 120 Hz. Simultaneous ±0 Hz and 60 Hz
rejection is obtained when the output data rate is set to 10 Hz
or ±0 Hz; 60 Hz only rejection is obtained when the output data
rate is set to 60 Hz. The AD7191 can be operated with the
internal clock, or an external clock can be used.
Bridge power-down switch
Offset drift: 5 nV/°C
Gain drift: 1 ppm/°C
Specified drift over time
Simultaneous 50 Hz/60 Hz rejection
Internal temperature sensor
Power supply: 3 V to 5.25 V
Current: 4.35 mA
Temperature range: –40°C to +105°C
Package: 24-lead TSSOP
The part operates with a power supply of ꢁ ꢀ to ±.2± ꢀ. It
consumes a current of 4.ꢁ± mA. It is available in a 24-lead
TSSOP package.
INTERFACE
2-wire serial
SPI, QSPI™, and MICROWIRE™ compatible
Schmitt trigger on SCLK
APPLICATIONS
Weigh scales
Strain gauge transducers
Pressure measurement
Medical and scientific instrumentation
FUNCTIONAL BLOCK DIAGRAM
AV
DV
DD
AGND
DGND REFIN(+) REFIN(–)
DD
AD7191
DOUT/RDY
SCLK
AIN1
AIN2
AIN3
AIN4
SERIAL
INTERFACE
AND CONTROL
LOGIC
Σ-Δ
ADC
PDOWN
CHAN
MUX
PGA
CLKSEL
BPDSW
PGA2
PGA1
TEMPERATURE
SENSOR
CLOCK
CIRCUITRY
MCLK1 MCLK2
ODR2 ODR1 TEMP
Figure 1.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2009 Analog Devices, Inc. All rights reserved.
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