Chapter 15

Interfacing

Tim Williams

15.1 Mixing Analog and Digital

The two main problems that face designers who have to integrate analog and digital circuits on the same 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.

15.1.1 Ground Noise

The high-frequency switching noise that was 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 can be achieved ...

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