OPA2188 datasheet(27/43 Pages) TI

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9.2.3 System Examples

9.2.3.1 24-Bit, Delta-Sigma, Differential Load Cell or Strain Gauge Sensor Signal Conditioning

The OPA2182 is used in a 24-bit, differential load cell or strain gauge sensor signal conditioning system

alongside the ADS1225. The OPA2182 amplifier is configured in a two-amp instrumentation-amplifier (IA)

configuration, and is band-limited to reduce noise and allow heavy capacitive drive. The load cell is powered by

an excitation voltage (denoted VEX) 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 VEX / 2.

In this example, the OPA2182 is employed here because of the excellent input offset voltage (0.45 µV) and

input offset voltage drift (0.003 µV/°C), the low broadband noise (5.7 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 a dedicated START pin.

ADS1225

AVDD

DVDD

GND

BUFEN

TEMPEN

MODE

+3 V

+5 V

+3 V

MSP430xxx

or other host

DVDD

VREFP

VREFN

GND

SCLK

DRDY / DOUT

START

OPAx182

+15 V

10 k

1 µF

GND

OPAx182

+15 V

1 µF

GND

Load Cell

OUT

+OUT

GND

VEX

RTRACE

+SENSE

SENSE

1 µF

1 k

10 µF

GND

AINP1

AINN1

GND

RTRACE

+5 V

10 k

G = 1 + t ®

t ® RF

G = 1 + t ®

Figure 9-7. 24-Bit Differential Load Cell or Strain Gauge Sensor Signal Conditioning Schematic

www.ti.com

OPA182, OPA2182, OPA4182

SBOS936D – DECEMBER 2019 – REVISED DECEMBER 2021

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