Univ 3 pin 2 use; PIC18F26K80

[Claude_Detier]

Hi,
Referring to the POE project with HAPCAN, I'm trying to create a fit-for-purpose voltage regulator (DC2DC output different than the 24V here). Specs of the PIC18F26K80 say; 1,8V-5.5V and it has an on-chip regulator 3.3V.
HAPCAN Univ 3 supplies 5V except for pin 2 : RA0 / CVref / AN0 / ULPWU which takes it's power or signal via R 51K/10K split from the 24V source (Vin from the MCP).

My question is; what is pin 2 used for ?
I was hoping ultra low-power wake-up input but in the HAPCAN docs it seems limited to AN0/RA0 (analog I/O or A/D ch0) without further explanation.
Can't I get this from the Vout behind the MCP1790 5002EDB ?
My next question is: Assuming I can get 3,3V what pins, resistors, capacitors don't need to be connected ? saving PCB space.

Thanks in advance,

[Jacek]

My question is; what is pin 2 used for ?...

Please have a look at figure 2 in https://hapcan.com/devices/universal/un ... _3cpub.pdf. The pin 2 is used as an analogue input to measure power supply voltage on the bus.

...Can't I get this from the Vout behind the MCP1790 5002EDB ?

You could, but it would measure 5V on MCP1790 output.

My next question is: Assuming I can get 3,3V what pins, resistors, capacitors don't need to be connected ? saving PCB space.

I don’t think you could remove any of them. For clarity please have a look at chapter 2 in processor datasheet. https://ww1.microchip.com/downloads/en/ ... pdf#page61