ZMD31020
Sensor Signal Conditioner
Datasheet
2.5.4 Temperature Measurement
The temperature sensing diode, selected by TS – configuration bit 5, is biased with a constant current of 40µA.
It‘s forward drop changes with –2.1mV/°K typically, and is passed as differential temperature signal. The 40µA
current source is only on during temperature measurement, to prevent any interference with the bridge sensor
signal's measurement. The differential temperature signal is resolved by the ADC with only 10 bits, against a
differential reference voltage of 0.980V, derived from an on-chip bandgap. Whenever measuring temperature,
the ADC is set to RSADC = 15/16.
2.6 Correction Microcontroller CMC
The CMC performs the sensor signal fine-tuning in the digital domain. It is a 16 bit RISC micro-controller, driven
by an on-chip clock generator with a nominal clock frequency of 1.5 MHz. The overall clock frequency tolerance
is smaller than 25%. The CMC includes a 16-bit width ALU and a (16 x 16)-bit RAM. Furthermore it has a 12-
bit input counter into which the ADC will serially transmit conversion results; 4096 clock cycles are needed per
result. The CMC is connected to a (1k x 16)-bit instruction ROM and a (12 x 16)-bit parameter EEPROM. At the
output side the CMC is equipped with an I2C-interface as a digital series output for the corrected sensor signal.
Initially, during calibration, the same interface is used bi-directionally: to write the configuration word into the
EEPROM, to read non-corrected sensor value as well as temperature, and again and finally to write the valid
calibration parameters into the EEPROM.
2.7 Parameter EEPROM
The parameter EEPROM is a non-volatile store for 12 parameter values, each with 16 bits of width.
Address
Parameter
Default content
5234 Hex
0023 Hex
2044 Hex
3022 Hex
6356 Hex
1045 Hex
2073 Hex
03E8 Hex
0FA0 Hex
0040 Hex
1234 Hex
5678 Hex
calibration parameter a0 for sensor's non-linearity correction
0HEX
1HEX
2HEX
3HEX
4HEX
5HEX
6HEX
7HEX
8HEX
9HEX
AHEX
BHEX
calibration parameter a1 for sensor's offset correction
calibration parameter a2 for first order sensor offset drift correction
calibration parameter a3 for second order sensor offset drift correction
calibration parameter a4 for gain correction
calibration parameter a5 for first order gain drift correction
calibration parameter a6 for second order gain drift correction
low-side scale limit value for corrected sensor signal
high-side scale limit value for corrected sensor signal
configuration word
customer-specific identification word
customer-specific identification word
Contents of the parameter EEPROM
The configuration word and it's contents under address &H09 have been described already in chapter 2.5.
The calibration parameters are stored under addresses &H00 through &H06. The calculation of these
parameters is described in the ZMD31020 Functional Description.
Copyright © 2004, ZMD AG, Rev. 1.6, 2005-05-19
7/19
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD [ Zentrum Mikroelektronik Dresden AG ]
