OPA189 Datasheet, PDF (27/34 Pages) Texas Instruments – Precision, 36-V, 14-MHz, MUX-Friendly Low-Noise, Rail-to-Rail Output, Zero-Drift Operational Amplifiers

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OPA189, OPA2189, OPA4189
SBOS830 – JUNE 2017
10 System Examples
10.1 24-Bit, Delta-Sigma, Differential Load Cell or Strain Gauge Sensor Signal Conditioning
OPAx189 is used in a 24-bit, differential load cell or strain gauge sensor signal conditioning system alongside the
ADS1225. A pair of OPAx189 amplifiers are configured in a two-amp instrumentation amplifier (IA) configuration
and are band-limited to reduce noise and allow heavy capacitive drive. The load cell is powered by an excitation
voltage (denoted V_EX) of 5-V and provides a differential voltage proportional to force applied. The differential
voltage can be quite small and both outputs are biased to V_EX / 2.
OPAx189 is employed here due to the excellent input offset voltage (0.4-µV) and input offset voltage drift
(0.0035-µV/°C), the low broadband noise (5.8-nV/√Hz) and zero-flicker noise, and excellent linearity and high
input impedance. The two-amp IA configuration removes the dc bias and amplifies the differential signal of
interest and drives the 24-bit, delta-sigma ADS1225 analog-to-digital converter (ADC) for acquisition and
conversion. The ADS1225 features a 100-SPS data rate, single-cycle settling, and simple conversion control with
the dedicated START pin.
2 ® R_F
G=1+
R_G
C4
0.1 nF
C5
0.1 µF
C6
0.1 nF
RTRACE
RTRACE
+SENSE
+OUT _-SENSE
+5V
+
VEX
±
GND
±OUT
Load Cell
GND
GND
+
OPAx189
±
+15V
RF
10 k
CF
1 µF
RG
50
CF
1 µF
RF
10 k
+15V
GND
GND
GND
VREFN
VREFP AVDD ^+5V
C1
10 µF
R1
1k
C2
1 µF
R2
1k
C3
10 µF
AINP1
AINN1
+3V
DVDD
START
DVDD
SCLK
DRDY / DOUT
ADS1225
MSP430xxx
or other host
MODE ^+3V
BUFEN
TEMPEN
GND
±
OPAx189
+
GND
GND
GND
Copyright © 2017, Texas Instruments Incorporated
Figure 19. 24-Bit, Differential Load Cell or Strain Gauge Sensor Signal Conditioning Schematic
Copyright © 2017, Texas Instruments Incorporated
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Product Folder Links: OPA189 OPA2189 OPA4189