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EMC DESIGN GUIDE FOR ST MICROCONTROLLERS

3.1.3.4 Internal Circuitry: Analog Input pin

Figure 16. shows the internal circuitry used for analog input. It is primarily a digital I/O with an

added analog multiplexer for the selection of the input channel of the Analog to Digital Con-

verter (ADC).

The presence of the multiplexer P-channel and N-channel can affect the behaviour of the pin

when exposed to illegal voltage conditions. These transistors are controlled by a low noise

verify the input voltage value with respect to both analog power supply and digital power

supply, in order to avoid unintentional current injections which (if not limited) could destroy the

device.

Figure 16. Digital Input/Output - Push-Pull Output - Analog Multiplexer Input

PIN

OUTPUT

BUFFER

P

N

P

N

N

INPUT

BUFFER

P

ESD PROTECTION

CIRCUITRY

PORT CIRCUITRY

I/O CIRCUITRY

P

EN

EN

P

P