Replacing the AD7689 with the GXSC ADC in Distributed Data Acquisition (DAQ) Cards

Distributed data acquisition (DAQ) cards are primarily deployed on production lines, at equipment terminals, and at outdoor measurement and control points, where they are responsible for the real-time acquisition, digital conversion, and remote upload of multiple analog signals. Compared to centralized data acquisition devices, distributed DAQs emphasize advantages such as multi-channel integration, compact and lightweight design, low-power operation, long-distance interference-resistant transmission, wide-temperature reliability, and strong batch consistency.

Distributed data acquisition cards operate by collecting data locally at the front end and uploading it remotely via a bus, and are deployed at various monitoring points throughout industrial sites. Given the complexity of on-site monitoring parameters, a single device must integrate multiple analog acquisition channels. GXSC’s 8-channel, 16-bit analog-to-digital converter integrates a multiplexer, a low-drift reference voltage source, an on-chip temperature sensor, and a programmable filter unit. This single-chip solution enables high-precision, time-division multiplexed acquisition of 8 analog signals with a maximum throughput rate of 250 kSPS, allowing for the construction of a complete multi-channel acquisition system without the need for complex peripheral circuits.

The GXSC ADC incorporates all the circuits required for a multi-channel, low-power data acquisition system. The SPI interface is used to write configuration registers and receive conversion results. A dedicated power supply (VIO) powers the SPI interface, and its power consumption is proportional to the sampling rate. The main features of the GXSC ADC are as follows:

Single-supply operation: 5 V

Logic interface voltage: 1.8 V to 5 V

8-channel multiplexer; inputs can be configured as Unipolar single-ended

Differential (using reference ground)

Pseudo-bipolar

Sampling rate: 250 kSPS

INL: Maximum 2.5 LSB

Dynamic range: 92.5 dB

SNDR: 91 dB (fiN = 1 kHz)

THD: –102 dB (fiN = 1 kHz)

Analog input range: OV to VREF (VREF can be as high as VDD)

Serial interface compatible with SPI/QSPI/MICROWIRE/DSP

Multiple reference source types Internal 4.096 V reference source

External buffered reference source (up to 4.096 V)

External reference source (up to VDD)

Channel sequencer, selectable single-pole filter, busy indicator

No pipeline delay, SAR architecture

Low power consumption: 15.5 mW (250 kSPS), 7 µW (100 SPS)

QFN 20 × 4 mm and WLCSP 20 × 2.4 mm packages