Replace AD7685 with GX7685 Single-Channel 16-Bit 1MSPS for Automated Test Equipment

One of the core functions of automated test equipment (ATE) is to perform fast and accurate quantitative evaluation of the DC parameters and AC characteristics of the device under test (DUT). The parametric measurement unit (PMU) is responsible for applying stimuli to the DUT and acquiring the response, while the analog-to-digital converter (ADC) determines the credibility of the measurement results. In a typical ATE architecture, the PMU chip integrates four-channel drive and measurement functions, but its output still requires an external ADC to complete digitization.

The measurement solution in this equipment can use the GX7685 16-bit 1MSPS ADC. Its 16-bit resolution achieves a balance among precision, power consumption, and interface flexibility. The 1MSPS throughput rate is sufficient to cover most DC parameter test scenarios without waiting for pipeline filling, which is particularly critical for ATE timing control that requires rapid channel switching.

On the rising edge of CNV, the GX7685 samples the analog input voltage difference between IN+ and IN−, ranging from 0V to REF. The reference voltage is provided externally and can be independent of the supply voltage. Power consumption and throughput rate vary linearly. The SPI-compatible serial interface also allows the SDI input to be used to daisy-chain several ADCs onto a three-wire bus and provides an optional busy indicator.

GX7685 Product Features:

• Pin-to-pin replacement for AD7685

• Throughput rate 1MSPS, 16-bit resolution

• Differential nonlinearity: ±0.8LSB

• Integral nonlinearity: ±2.0LSB

• Signal-to-noise and distortion ratio: 86dB@1KHz

• Total harmonic distortion: −100dB@1KHz

• External reference: 2.5V–5V selectable

• Single analog supply VDD: 2.5V

• Logic interface supply VIO: 1.8V~5.5V

• No pipeline delay

• Configurable input modes: single-ended input, unipolar input, pseudo-differential input

• 10-lead 3mm×3mm DFN package

• Power consumption: 7.7mW@Fs=1MSPS

• Standby current: 50nA

• Compatible with 1.8V, 2.5V, 3.3V, and 5V logic when using an independent VIO supply