Pepper Computer Modular Computers RS232 User Manual

SMART I/O User’s Manual

March 12, 1996

©1996 PEP Modular Computers GmbH

Page 5 - 10

Chapter 5  Analog Modules

The SM-DAD1 has 4 differential voltage inputs and 2 unipolar/bipolar

voltage outputs. An on-board EEPROM contains board specific calibration

data, module ID byte and production data. An on-board switched-mode

regulator provides 

±

15V for the analog I/O and an additional linear regulator

provides the -5V required by the ADC.

The input circuitry of the SM-DAD1 consists of an R-C first-order, low-pass

filter to prevent noise and signals greater than 10kHz from entering the

system, a 1:4 channel multiplexer, followed by a differential amplifier,

divider and a 12-bit fast analog to digital converter (ADC).

The ADC, using successive approximation and input track and hold is

referenced by its own on-chip voltage source supplying 4.096V. To cater for

bipolar full-scale inputs, this reference source is split (-2.048V .. +2.048V).

The incoming voltage signals are multiplexed and reduced via a 1:5 divider

network so that the ADC is supplied with a scalable input voltage range.

Low Pass

Filter

Voltage

Source

-10 .. +10V

Single

Ended

AGND

+

-

MUX

4:1

Input

Amplifier

ADC

System

Interface