Electronic – arduino – the function of this diode in arduino uno(between +5V and reset)


I am doing my own avr dev board using atmege32a and basically I am looking into Arduino uno board design and try to mimic the common parts for best practices
like for example power and other stuff

I have noticed that there is a diode between the +5V rail and the reset pin and also the 10K resistor.

The resistor is for the pull-up that is obvious, but I do not understand what this diode doing in this place ?


I have added the whole schematic from arduino website


Arduino Uno Diode-Reset

Best Answer

I doubt that this diode is ESD related nor that it has anything to do with a high-voltage programming mode. As far as I know you can program an Atmega from the normal supply voltage (no high voltage needed).

I think it is there to quickly pull down the not-reset signal when the 5 V supply line becomes low (off).

Very likely there will be a capacitor (to ground) on that reset input to keep the MCU in reset while allowing everything to settle after the +5 V supply becomes active. To guarantee that this will also happen when the supply is (shortly) interrupted that capacitor needs the be discharged quickly. That is what this diode will do !