Author Topic: PIC Microcontroller - Max Current Source Question.  (Read 6268 times)

demonstar

PIC Microcontroller - Max Current Source Question.
« on: October 08, 2008, 10:42:23 AM »
The datasheet for a PIC I am using says that the maximum current sourced from any output is 25mA and a total of 250mA into the VDD pin. If I tried to source more than the allowed total 250mA (well prob 240mA by the time the power for the running of the PIC is taken off) from the chip would it allow me to do so and damage the chip or not allow me to do so and just cap the current at the max? In otherwords will it prevent anymore than the max. current (250mA) being taken into the VDD pin or will it take more than that in and ultimately kill itself?

Thanks.
"If A is success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut"  Words of Albert Einstein

mutant_guitar

Re: PIC Microcontroller - Max Current Source Question.
« Reply #1 on: October 08, 2008, 11:44:17 AM »
if the chip doesn't die, it will probably not function properly. i've had this problem before when hooking a 5v uc to a 3.3v FPGA. it didn't damage either, but some weird stuff  happened. i don't know how the PIC will handle being overloaded, but i wouldn't try to find out.

if you need more current than the PIC can provide, then you should look into adding some sort of transistor switching circuit to your outputs.

demonstar

Re: PIC Microcontroller - Max Current Source Question.
« Reply #2 on: October 08, 2008, 01:34:35 PM »
Quote
f you need more current than the PIC can provide, then you should look into adding some sort of transistor switching circuit to your outputs.

I'm making a experimenting board for PICs. I'll have a board with velcro on that I can velcro modules to. The modules will include oscillators, LED arrays, LCDs, a motor and breadboard etc. I just know this will be something I'll use for a while to come. I'm documenting it (Like an operating manual) so when I come to use it in the future when my mind isn't so fresh, I know exactly what it is safe to do with it and what it is not safe to do with it. I'm just trying to work out if I can overload it or if it prevents that so I can document it. :icon_biggrin:
"If A is success in life, then A equals x plus y plus z. Work is x; y is play; and z is keeping your mouth shut"  Words of Albert Einstein

mutant_guitar

Re: PIC Microcontroller - Max Current Source Question.
« Reply #3 on: October 08, 2008, 04:06:18 PM »
lol, PICs are cheap, might as well blow one up.

anyway, sounds like a neat little project.

Inventor

Re: PIC Microcontroller - Max Current Source Question.
« Reply #4 on: October 09, 2008, 02:48:08 PM »
I'm making a experimenting board for PICs. I'll have a board with velcro on that I can velcro modules to. The modules will include oscillators, LED arrays, LCDs, a motor and breadboard etc. I just know this will be something I'll use for a while to come. I'm documenting it (Like an operating manual) so when I come to use it in the future when my mind isn't so fresh, I know exactly what it is safe to do with it and what it is not safe to do with it. I'm just trying to work out if I can overload it or if it prevents that so I can document it. :icon_biggrin:

Cool, demonstar, I'm working on a similar project called EChucK.  It's a PIC-based modular synthesizer that can be used for making guitar effects.  It's open-sourced hardware if there is such a thing so you can copy my work if you like, or you might want to contrubute.  In fact, I think I'll post about it in another thread.  Great minds think alike!  Cheers!