AS8500 Data Acquisition Front-End IC

Description

The AS8500 is a complete, low power multi purpose data acquisition system for very small signals (i.e. voltages from shunt resistors, thermocouples) that operates on a single 5 V power supply.

The AS8500 has four ground refering inputs which can be switched separately to the internal PGA. Two input channels can also be operated as a fully differential ground free input. The system can measure both positive and negative input signals.

Key Features

The AS8500 / AS8501 product family for high precision data acquisition systems is dedicated to the measurement of small voltages close to ground (for both polarities above or below ground).

The highlights are:

• High resolution (16 bit, up to 21 bit by external averaging)
• Low noise (0.1 uV RMS for 0-5Hz)
• High linearity (< 0.1%)
• No offset
• Sampling rates from 2 Hz up to maximum 8 kHz
• Fast dual channel measurement (quasi synchronous)
• High flexibility due to many special features
• Single 5V supply

Multiple input channels, configurable as:

• 4 single ended channels
• or 2 fully differential inputs
• With or without programmable pre-amplifier
• Programmable current sources

Choices for full scale input range versus ground:

• ±7.5mV, ±5mV, ±30mV, ±120mV or +800 / -300mV

Bidirectional serial interface to µC.

Basic application targets:

• Current measurement through low ohmic shunt (100 µΩ range)
• Resistive or thermocouple temperature sensing
• General purpose sensor interface for half- or full bridge sensors
• True resistance measurement through delta U by delta I measurement
• Compensation of EMF voltages by biased and unbiased sequential measurements
• Error compensation by comparing a sensing device with a reference device through different input channels but using same measurement path to eliminate mismatch of preamplifiers and filters

Applications

• Battery management for automotive systems
• Power management
• mV/µV-meter
• Thermocouple temperature measurement
• Precision temperature measurement
• High-precision voltage and current measurement

Block Diagram