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Protect I/Os DAC and ADC of my STM32F4

Question asked by v.claire on Aug 27, 2014
Latest reply on Aug 29, 2014 by Reupri.Alban
Hello everybody!

On my board, I want to protect ADC and DAC pins for my STM32F407.

Theses I/Os are linked to audio connectors JACK 6.35, the user will be able to plug any 6.35 cables on the connectors. I don't want my uC to be damaged if the user did something wrong, for example we can imagine:
- Plug a jack supplying a voltage varying between -30V and 30V on the ADC input.
- Even worse, plug a jack supplying a voltage varying between -30V and 30V on the DAC output.

Attached, I designed a circuit inspired of what I found on the internet and on this forum, with bidirectional ESD diodes PESD5V0S1BA

ADC INPUT: a divider bridge converts the connector jack +5V to +3.3V for the uC

DAC OUTPUT: an opamp amplifies the uC +3.3V to +5V for the jack connector .

What do you think about this design? Is my system well protected against bad uses?

Thanks a lot!