Analog Devices: CN0255 Reference Design for A Complete Single-Supply, 16-Bit, 100 kSPS PulSAR ADC System Dissipates 8 mW

Kit Overview

In most systems, there are tradeoffs between performance and low power. The focus of this circuit design EVAL-CN0255-SDPZEVAL-CN0255-SDPZ is to explore a few of these tradeoffs and still achieve low power (8 mW typical) and high performance in a 16-bit, 100 kSPS data acquisition system.

This circuit uses the AD7988-1AD7988-1, a low power (350 μA) PulSAR analog-to-digital converter (ADC), driven directly from the ADA4841-1ADA4841-1 high performance, low voltage, low power op-amp. This amplifier was chosen for its excellent dynamic performance and its ability to operate with a single-supply voltage and to provide a rail-to-rail output. In addition, the input common mode voltage range includes the negative rail.

The AD7988-1 ADC requires an external voltage reference between 2.4 V and 5.1 V. In this application, the voltage reference chosen was the ADR4525ADR4525 precision 2.5 V reference. The EVAL-CN0255-SDPZEVAL-CN0255-SDPZ evaluation board was interfaced to the System Demonstration Platform (SDP-B), EVAL-SDP-CB1ZEVAL-SDP-CB1Z, where the ADC SPI-compatible serial interface was connected to the DSP SPORT interface. The ADCs SPI interface features the ability to daisy-chain several ADCs on a single 3-wire bus. It is compatible with 1.8 V, 2.5 V, 3 V, or 5 V logic, using the separate VIO supply pin.

The heart of this circuit is the AD7988-1, a 16-bit, 100 kSPS successive approximation, ADC that operates from a single VDD power supply. It contains a low power, high speed, 16-bit sampling ADC and a versatile serial port interface (SPI). On the CNV rising edge, it samples an analog input, IN+, between 0 V to REF with respect to the ground sense pin, IN−. The reference voltage, REF, is applied externally and can be set independent of the supply voltage, VDD.

Key Applications: Electronic Test & Measurement, Programmable Logic Controllers/ Distributed Control Systems