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does analog input need protection?

MMoha.71
Associate

I design a stm32h743 board without conformal coating

, it works good, when I shacked board, stm32h743 failed and burnt.

what's that reason?

thank you

1 ACCEPTED SOLUTION

Accepted Solutions
LCE
Principal II

Independent of coating, every IO of an active component / controller / SoC / whatever should be protected, unless it has some built-in protection (usually only specialized IO drivers), OR the connected circuitry - e.g. a voltage and current limited driver, or an open collector circuit - assures that the maximum ratings cannot be reached.

Protection can be as simple as a small value series resistor, or TVS diodes, ...

I would also recommend to never directly connect a controller pin to the outside world, except for only internally accessible programming / debug pins. Use drivers / receivers, plus protection circuits (and also think about where the surplus energy goes).

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2 REPLIES 2
Uwe Bonnes
Principal III

Voltages and current with value near and above absolute maximum rating will kill the device.

LCE
Principal II

Independent of coating, every IO of an active component / controller / SoC / whatever should be protected, unless it has some built-in protection (usually only specialized IO drivers), OR the connected circuitry - e.g. a voltage and current limited driver, or an open collector circuit - assures that the maximum ratings cannot be reached.

Protection can be as simple as a small value series resistor, or TVS diodes, ...

I would also recommend to never directly connect a controller pin to the outside world, except for only internally accessible programming / debug pins. Use drivers / receivers, plus protection circuits (and also think about where the surplus energy goes).