ZMD31010 参数 Datasheet PDF下载

ZMD31010

RBic

Lite

TM

Low-Cost Sensor Signal Conditioner

Datasheet

1.2

Analog Front End

1.2.1 Bandgap/PTAT and PTAT Amplifier

The Bandgap/PTAT provides the PTAT signal to the ADC, which allows accurate temperature conversion. In

addition, the ultra-low ppm Bandgap provides a stable voltage reference over temperature for the operation of

the rest of the IC.

The PTAT signal is amplified through a path in the pre-amp and fed to the ADC for conversion. The most

significant 12-bits of this converted result are used for temperature measurement and temperature correction

of bridge readings. When temperature is output in digital mode only the most significant 8-bits are given.

1.2.2 Bridge Supply

The voltage driven bridge is usually connected to V

DD

and ground. As a power savings feature, the RBic

Lite

™

also includes a switched transistor to interrupt the bridge current via pin 1 (Bsink). The transistor switching is

synchronized to the A-to-D conversion and released after finishing the conversion. To utilize this feature, the

low supply of the bridge should be connected to Bsink instead of ground.

Depending on the programmable update rate, the average current consumption (including bridge current) can

be reduced to approximately 20%, 5% or 1%.

1.2.3 Pre-Amp Block

The differential signal from the bridge is amplified through a chopper-stabilized instrumentation amplifier with

very high input impedance designed for low noise and low drift. This pre-amp provides gain for the differential

signal and re-centers its DC to V

DD

/2. The output of the Pre-Amp block is fed into the A-to-D converter. The

calibration sequence performed by the digital core includes an auto zero sequence to null any drift in the

Pre-Amp state over temperature.

The Pre-Amp is nominally set to a gain of 24. Other possible gain settings are 6, 12, and 48.

The inputs to the Pre-Amp from (VBN/VBP pins) can be reversed via an EEPROM configuration bit.

1.2.4 Analog-to-Digital Converter (ADC)

A 14-bit/1ms 2

nd

order charge-balancing ADC is used to convert signals coming from the pre-amplifier. The

converter, designed in full differential switched capacitor technique, is used for converting the various signals

in the digital domain. This principle offers the following advantages:

•

•

•

High noise immunity because of the differential signal path and integrating behavior

Independent from clock frequency drift and clock jitter

Fast conversion time owing to second order mode

Four selectable values for the zero point of the input voltage allow conversion to adapt to the sensor’s offset

parameter. Together with the reverse input polarity mode, this results in four possible zero point adjustments.

The conversion rate varies with the programmed update rate. The fastest conversation rate is 1k samples/s

and the response time is then 1ms. Based on a best fit, the Integral Nonlinearity (INL) is less then 4 LSB

14Bit.

RBic

Lite

™ Datasheet, Rev. 1.2, February 28, 2006

Page 5 of 38

© ZMD AG, 2006

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.