The GXSC ADC, which replaces the AD7124, is widely used in bridge-type sensors

Bridge-type sensors (such as strain gauge bridges, pressure bridges, and load cells) operate based on the Wheatstone bridge structure. When a physical quantity being measured acts on the sensor, the resistance of the bridge arms undergoes a slight change, resulting in a weak differential voltage signal at the bridge output. The signal amplitude typically ranges from a few millivolts to several tens of millivolts and is susceptible to external interference, posing significant challenges for signal acquisition.

 

The GXSC ADC addresses the primary challenges of bridge sensor signal acquisition through a fully integrated analog front-end design. The chip integrates multiple functions to reduce system costs and component count in sensor measurement applications, featuring a low-noise, programmable-gain amplifier, a single-cycle steady-state digital filter, and an internal oscillator.

The GXSC ADC also provides a built-in low-drift voltage reference and two matched, programmable excitation current sources. The input multiplexer supports eight differential inputs; additionally, the multiplexer integrates sensor burnout detection, thermocouple voltage bias, system monitoring, and general-purpose digital I/O. The PGA offers selectable gain up to 128 V/V.

 

These features provide a complete front-end solution for sensor measurement applications, including thermocouples, thermistors, and resistance temperature detectors, as well as other small-signal measurements, such as bridge-type sensors. The digital filter stabilizes within a single cycle to support fast channel switching when using the input multiplexer and provides data rates up to 19.2 kSPS. For certain data rates, the filter suppresses 50 Hz and 60 Hz interference. Its key performance advantages are as follows:

• Effective resolution: 23 bits

• Number of channels: 16 single-ended / 8 differential pairs

• Output rate: Up to 19.2 kSPS

• High integration:

› Integrated internal reference: 8 ppm/°C temperature drift, 2.5 V

› Programmable differential amplifier (integrated high-impedance PGA): 0.02% initial accuracy

› Integrated 2-channel IDACs with 0.1% matching

› Integrated bias voltage and open-circuit detection

› Integrated temperature sensor with 2°C accuracy

• Supports simultaneous 50/60 Hz suppression

• Single-cycle settling and automatic channel scanning

• Supports SPI CRC verification

• Digital supply: 2.7 V to 5.25 V

• Analog Power Supply: Unipolar (2.7V–5.25V) & Bipolar (±2.5V)

• Package: 5.00mm × 5.00mm QFN (32-pin)

• Operating Temperature Range: –40°C to +125°C