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SMART I/O User’s Manual

Chapter 5 Analog Modules

5.4.5 Functional Description

The SM-ADC1 has 6 differential voltage or current inputs depending on the

ordered type. An on-board EEPROM contains board specific calibration

data, module ID byte, sub ID byte and production data. A DC/DC converter

generates the 5V to ±15V power requirements for the ADC converter and

provides additional system isolation.

5.4.5.1 Input Circuitry

The input circuitry of the SM-ADC1 consists of an R-C first-order, low-pass

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

system, a 1:6 channel multiplexer, followed by a differential amplifier,

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

Figure 5.4.5.1: SM-ADC1 Input Shematic Diagram

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

8:1

Input

Amplifier

ADC

System

Interface

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Pepper-computer Modular Computers RS485 Manuale Utente Pagina 247