1 Features

1• 16-Bit ADCs with Integrated Analog Front-End

• 4-, 8-Channel MUX with Auto and Manual Scan

• Channel-Independent Programmable Inputs:

– ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, ±0.64 V

– 10.24 V, 5.12 V, 2.56 V, 1.28 V

• 5-V Analog Supply: 1.65-V to 5-V I/O Supply

• Constant Resistive Input Impedance: 1 MΩ analog•

Input Overvoltage Protection: Up to ±20 V

• On-Chip, 4.096-V Reference with Low Drift

• Excellent Performance:

– 500-kSPS Aggregate Throughput

– DNL: ±0.5 LSB; INL: ±0.75 LSB

– Low Drift for Gain Error and Offset

– SNR: 92 dB; THD: –102 dB

– Low Power: 65 mW

• AUX Input → Direct Connection to ADC Inputs

• ALARM → High and Low Thresholds per Channel

• SPI™-Compatible Interface with Daisy-Chain

• Industrial Temperature Range: –40°C to 125°C

• TSSOP-38 Package (9.7 mm × 4.4 mm)

2 Applications

• Power Automation

• Protection Relays

• PLC Analog Input Modules

3 Description

The ADS8684A and ADS8688A are 4- and 8- channel, integrated data acquisition systems based

on a 16-bit successive approximation (SAR) analog•

to-digital converter (ADC), operating at a throughput

of 500 kSPS. The devices feature integrated analog front-end circuitry for each input channel with

overvoltage protection up to ±20 V, a 4- or 8-channel

multiplexer with automatic and manual scanning

modes, and an on-chip, 4.096-V reference with low

temperature drift. Operating on a single 5-V analog

supply, each input channel on the devices can

support true bipolar input ranges of ±10.24 V,

±5.12 V, ±2.56 V, ±1.28V and ±0.64V, as well as

unipolar input ranges of 0 V to 10.24 V, 0 V to 5.12 V, 0 V to 2.56 V and 0 V to 1.28 V. The gain of the

analog front-end for all input ranges is accurately

trimmed to ensure a high dc precision. The input

range selection is software-programmable and independent for each channel. The devices offer a

1-MΩ constant resistive input impedance irrespective

of the selected input range.

The ADS8684A and ADS8688A offer a simple SPIcompatible

serial interface to the digital host and also

support daisy-chaining of multiple devices. The digital

supply operates from 1.65 V to 5.25 V, enabling

direct interface to a wide range of host controllers.