Application of 24 bit 16 channel high integration AFE GX7124 benchmark AD7124 in thermocouples and thermistors

Thermocouples and thermistors are the two most widely used temperature sensors. Thermocouples are characterized by a wide temperature measurement range (-270 ℃~1800 ℃) and high temperature resistance, making them suitable for high-temperature environments; Thermistors are suitable for precise measurement at medium and low temperatures with high precision (± 0.1 ℃) and sensitivity. This article introduces a 24 bit 16 channel highly integrated AFE GX7124 for thermocouple and thermistor measurement. GX7124 is comparable to TI‘s AD7124 and has a certain price advantage and stable supply channel.

Thermocouples can generate voltage that varies with temperature. Due to the extremely small thermoelectric potential of thermocouples, the voltage variation of thermistors is often as low as millivolts. By optimizing the ∑ - Δ modulator architecture, GX7124 supports 50/60Hz simultaneous suppression, and with a 24 bit resolution, it can accurately detect signal changes at the microvolt level.

GX7124 integrates multiple functions to reduce the system cost and component count of sensor measurement applications. GX7124 features a low-noise, programmable gain amplifier, equipped with a single cycle steady-state digital filter and internal oscillator. GX7124 also provides a built-in low drift voltage reference and two matching programmable excitation current sources. The input multiplexer supports 8 differential inputs. In addition, the multiplexer integrates sensor burnout detection, thermocouple voltage bias, system monitoring, and universal digital I/O. PGA offers selectable gain up to 128V/V.

These features provide a complete front-end solution for temperature sensor measurement applications, including thermocouples, thermistors, resistance temperature detectors, and other small signal measurements, including resistance bridge sensors. Digital filters are stable within a single cycle to support fast channel switching when using input multiplexers and provide data rates of up to 19.2kSPS. For certain data rates, filters will suppress interference at 50Hz and 60Hz. Its main performance advantages are as follows:

• Effective resolution: 23bits

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

• Output rate: up to 19.2kSPS

• High integration:

Integrated internal benchmark: temperature drift 8ppm/℃, 2.5V

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

Integrate 2 channels with 0.1% matching degree IDAC

Integrated Bias voltage and wire breakage detection

Integrated 2 ℃ precision temperature sensor

• Supports 50/60Hz simultaneous suppression

Single cycle establishment and automatic channel scanning

• Support SPI CRC verification

Digital power supply: 2.7V~5.25V

• Analog power supply: unipolar (2.7V~5.25V)&bipolar (± 2.5V)

• Package: 5.00mm x 5.00mm QFN (32pin)

• Operating temperature range: -40 ° C to+125 ° C