1 Features
1• 12-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
• Input Overvoltage Protection: Up to ±20 V
• On-Chip, 4.096-V Reference with Low Drift
• Excellent Performance:
– 500-kSPS Aggregate Throughput
– DNL: ±0.2 LSB; INL: ±0.2 LSB
– Low Drift for Gain Error and Offset
– SNR: 73.8 dB; THD: –95 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 ADS8664 and ADS8668 are 4- and 8-channel, integrated data acquisition systems based on a 12-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 ADS8664 and ADS8668 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.