AS8501 Data Acquisition Front-End IC

Description

The AS8501 is a complete, low power data acquisition system for very small signals (i.e. voltages from shunt resistors, thermocouples) that operates on a single 5 V power supply.

It is factory trimmed for minimum temperature drift and absolute voltage output.

The AS8501 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 max. 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, ±15mV, ±30mV, ±120mV or +800 / -300mV

Bidirectional serial interface to µC.

Basic application targets:

• Current measurement through low ohmic shunt (100 µOhm 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