1 Features

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

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

• Channel-Independent Programmable Input

Ranges:

– Bipolar: ±10.24 V, ±5.12 V, ±2.56 V

– Unipolar: 10.24 V, 5.12 V

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

• Constant Resistive Input Impedance: 1 MΩ

• 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

• 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 ADS8684 and ADS8688 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, and ±2.56 V, as well as unipolar input

ranges of 0 V to 10.24 V and 0 V to 5.12 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 ADS8684 and ADS8688 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.