PIC24FJ512GU/GL406 POR Issue

Mrinmoy · Joined: 20 Dec 2023 Posts: 16

Hi,

I am using PIC24FJ512GL/GU406 both MCU(Anyone at a time) in one of my project with our own pcb board and using CCS version 5.101. The control board contains two mcu each performs its own different purpose. Sometimes we are facing a problem that after power on anyone of the mcu is not even enter in start of the firmware program i.e. main(). I have confirmed this by set one output led at the 1st line of the main(). When the problem occures the led is not turned on.
After power off the system again power on will solve the issue. But on a average count of 15 times power on & off this problem occurs 6-8 times.
Any light up on this issue will be highly appreciated.

Thanks in advance.

temtronic · Posted: Tue Mar 11, 2025 5:38 am

hmm....

Sounds like a problem in how you designed/built the power supply section of the PCB. Is it rated for at least 3x max running current ? IE say the unit needs 3 amps when running, PSU should be able to supply 9 amps.

Does EVERY 'chip' have a bypass cap close to it's VDD, VSS lines ?

If those PICs have 2 VDD, 2VSS are they ALL connected ?
I'm sure others ,who use those PICs will know of other possibilites.

Ttelmah · Joined: 11 Mar 2010 Posts: 19730

As Jay says, the most likely thing is power.
The PIC has a specification for the minimum rise time for the supply rail
for the internal POR to work. For the GU, look at DC17A in the electrical
characteristics. If the supply rises slower than this the POR won't work.
You need to either ensure your supply meets the specifications, or add
tour own external reset circuit to MCLR.
Too much capacitance on the supply rail relative to what it can deliver
on start up, is the normal cause.