as8500 austriamicrosystems, as8500 Datasheet

as8500

Manufacturer Part Number

as8500

Description

Low Power Data Acquisition System

Manufacturer

austriamicrosystems

Datasheet

1.AS8500.pdf (1 pages)

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1.1

Features

Applications

General description

The AS8500 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. The chip powers up with a set of default

conditions at which time it can be operated as a read-only-

converter. Reprogramming is at any time possible by just

writing into two internal registers via the serial interface.

The AS8500 has four ground referring 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.

The PGA amplification ranges from 6 to 100 which

enables the system to measure signals from 7mV to 120

mV full scale range with high accuracy, linearity and

speed.

The chip contains a high precision band gap reference

and an active offset compensation that makes the system

offset free (better than 0,5 μV) and the offset-TC value

AS8500

Universal multi purpose data acquisition system

16 bits resolution

differential inputs

Single + 5V supply

Low power 15 mW

SOIC16 package

Self- and system-calibration

16 kHz maximum sampling frequency

Internal temperature measurement

Internal reference

Programmable current sources

Digital comparator

Active wake-up

PGA gains 6, 24, 50, 100

Zero offset

Zero offset TC

Extremely low noise

Internal oscillator with comparator for active wake up

3-wire serial interface, μP compatible

Temperature range – 40 to + 125 °C

Battery management for automotive systems

Power management

mV/µV-meter

Thermocouple temperature measurement

RTD precision temperature measurement

High-precision voltage and current measurement

with auto-calibration on power up

ETR

ETS

VBAT

RSHH

RSHL

negligible. The built-in programmable digital filter allows an

effective noise suppression if the high speed is not necessary in

the application.

The input noise density is only 35 nV /

internal chopping frequency the system is free of 1/f-noise down

to DC. The 0-10 Hz noise is typical below 1 µV i.e. as good or

better than any other available chopper amplifier.

For high speed synchronous measurements the chip can run in an

automatic switching mode between two input channels with pre-

programmed parameter sets.

The circuit has been optimised for the application in battery

management systems in automotive systems. As a front end data

acquisition system it allows an high quality measurement of

current, voltage and temperature of the battery.

With a high quality 100 μΩ resistor the system can handle the

starter current of up to 1500 A, a continuous current of ± 300 A as

well as the very low idle current of a few mA in the standby mode.

For external temperature measurement the chip can use a wide

variety of different temperature sensors such as RTD, PTC, NTC,

thermocouples or even diodes or transistors. A built-in

programmable current source can be switched to any input and

activate these sensors without the need of other external

components.

The measurement of the chip temperature with the integrated

internal temperature sensor allows in addition the temperature

compensation of sensitive parameters which increases the total

accuracy considerably.

The flexibility of the system is further increased by a digital

comparator that can be assigned to any measured property

(current, voltage, temperature) and an active wake-up in the

sleep-mode.

All analog input-terminals can be checked for wire break via the

SDI-interface.

Figure 1: Functional Block Diagram

INTERNAL TEMPERATURE

PROTECTION

INPUT MUX

CHOPPER

SOURCES

CURRENT

16 BIT - CONVERTER

LEVEL SHIFT

SERIAL INTERFACE / CONTROL REGISTERS

REF

BUF

PGA

and

SCLK

REFERENCE

1.26 V

SDAT

AGND

and due to the high

COMPARATOR

CONTROLLER

CALIBRATION

DATA SHEET

VDDA

INT. CLOCK

INTN

FILTER

TIMER

DATA

DSP

Fact Sheet

VSSA

CLK

VDDD

VSSD

EZPRG

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