AS8501 datasheet(2/41 Pages) AMSCO

2 / 41 page

1.1

DATA SHEET

Revision 1.1, 04-April-06

www.austriamicrosystems.com

Page 1 of 40

Features

16 bits resolution

Differential inputs

Single + 5V supply

Low power 15 mW

SOIC16 package

Self- and system-calibration

with auto-calibration on power up

16 kHz maximum sampling frequency

Internal temperature measurement

Internal factory trimmed precision reference

Programmable current sources

Digital comparator

Active wake-up

PGA gains 1, 6, 24, 50, 100

Zero offset

Zero offset TC

Extremely low noise

Internal oscillator with comparator for active wake up

3-wire serial interface,

!P compatible

Temperature range – 40 to + 125 °C

Individual 24-bit serial number

Applications

Battery management for automotive systems

Power management

mV/µV-meter

High-precision voltage and current measurement

General 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. 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 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.

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 bandgap reference and an

active offset compensation that makes the system offset free

(better than 0,5

!V) and the offset-TC value 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 / Hz and due to

the high 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

!" 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.

Sensor specific data can be stored in the internal Zener-Zap memory and

are used to calibrate each measurement in the internal data processing

unit before transmission to the external µC via the serial SDI interface.

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.

INTERNAL TEMPERATURE

INPUT MUX

CHOPPER

PROTECTION

CURRENT

SOURCES

ETR

ETS

RSHH

RSHL

VBAT

16 BIT - CONVERTER

BUF

SERIAL INTERFACE / CONTROL REGISTERS

DSP

CONTROLLER

FILTER

INT. CLOCK

TIMER

CALIBRATION

DATA

COMPARATOR

1.26 V

REFERENCE

SCLK

SDAT

INTN

REF

AGND

VDDA

VSSA

VDDD

VSSD

CLK

EZPRG

PGA

and

LEVEL SHIFT

AS8501

Data Sheet

High precision voltage and current measurement sensor interface

Figure 1: Functional Block Diagram

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