Chapter 13

Interfacing

Tim Williams

13.1 Mixing Analog and Digital

The two main problems which face designers who have to integrate analog and digital circuits on the same printed circuit board (PCB) are:

• preventing digital switching noise from contaminating the analog signal, and

• interfacing the wide range of analog input voltages to the digital circuit.

Generating analog outputs from digital signals is not usually a problem. Generating digital inputs from analog signals is.

13.1.1 Ground Noise

The high-frequency switching noise discussed earlier must be kept out of analog circuits at all costs. An analog-to-digital interface quantizes a variable analog signal into a digital word, and the number of bits in the word determines the resolution that ...

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