SMART I/O User’s Manual | Chapter 5 Analog Modules |
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5.1.5 Functional Description
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.
5.1.5.1 Input Circuitry
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).
Figure 5.1.5.1: SM-DAD1 Input Schematic Diagram
+
Low Pass
-Filter
Single
Ended
AGND
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.
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Page | 5 - 10 | ©1996 PEP Modular Computers GmbH | March 12, 1996 |
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