Copyright © 2004, ZMD AG, Rev. 0.7, 2004-09-02, PRELIMINARY

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ZMD31050

Advanced Differential Sensor Signal Conditioner

Datasheet

PRELIMINARY

1.

Circuit Description

1.1

Signal Flow

Fig.3: Block diagram of ZMD31050

PGA

programmable gain amplifier

MUX

multiplexer

ADC

analog-to-digital converter

CMC

calibration microcontroller

DAC

digital-to-analog converter

FIO1

flexible I/O 1: analog out (voltage/current), PWM2,

ZACwire

FIO2

flexible I/O 2: PWM1, SPI data out, SPI slave select, Alarm1, Alarm2

SIF

serial interface: I2C data I/O, SPI data in, clock

PCOMP

programmable comparator

EEPROM

for calibration parameters and configuration

TS

on-chip temperature sensor (pn-junction)

ROM

for correction formula and –algorithm

PWM

PWM module

The ZMD31050’s signal path is partly analog (blue) and partly digital (red).

The differential signal from the bridge sensor is pre-amplified by the programmable gain amplifier

(PGA). The Multiplexer (MUX) transmits the signals from bridge sensor, external diode or separate

temperature sensor to the ADC in a certain sequence (instead of the temp. diode the internal pn-

junction (TS) can be used optionally). Afterwards the ADC converts these signals into digital values.

The digital signal correction takes place in the calibration micro-controller (CMC). It is based on a

special correction formula located in the ROM and on sensor-specific coefficients (stored into the

EEPROM during calibration).