Below I have attached a circuit which divides the voltage and gives the output to an input pin of a microcontroller.
- Input voltage = 24V
The resistor R0012 is for current limiting. The Zener diode breakdown voltage is 5.1V.
The microcontroller which I am using is - Microcontroller Datasheet
I could not see an GPIO input pin internal architecture of diagram inside the microcontroller datasheet.
I tried to simulate this portion of the circuit with the MCU end floating. I found that the voltage before R0012 is 2.9486561V and after R0012 is 2.9486144V. The current through it was 2.953uA. I couldn't understand how this current is obtained (even though I left the other end of the diode floating - nothing connected at the MCU end.)
My objective :
- I want to calculate the maximum power dissipation of the R0012 current limiting resistor. I know that it will not dissipate a huge amount. Just want to understand.
The microcontroller datasheet attached mentions a GPIO sink current of +3mA max. So, what would be the current flowing into the microcontroller pin in my case and what would be the voltage detected at the MCU pin?
How to go about calculating the power dissipation of the resistor?
How did my simulation show a current of 2.953uA?