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Microcontroller VDD Supply

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Sep 25, 2011
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Problem with Microcontroller VDD Supply


I am using dsPIC33FJ06GS202 controller. The TLV2217 LDO (Linear Voltage Regulator 12Vdc to 3.3Vdc) is supplying the 3.3VDD to the controller. But, its regulating 3.3V triangular signal which goes to the controller. Do you thing is there any effect on the output signal of the controller (i.e. The controller output is PWM signal) if the LDO supplies the triangular signal instead of DC signal.
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Ok first I want to say hmm.. odd :)
ok so question, what is a 3.3V triangle signal? is it doing a triangle from 0 to 3.3 and back to 0, or is there a triangle patter superimposed on the 3.3 so its going from say 2.7 to 3.7V? I would say the question you should be asking is.. why do i have a triangle coming from a regulator...
Perhaps it is unstable? perhaps you have coupling with another signal? or perhaps its power supply is a triangle? heh
I would say that yes a triangle supply on a pic can do nasty things, such as turning the device on and off. or you may see brown conditions occurring. Just bad..stuff can happen with a triangle supply. if the triangle is noise in the form of a few mV then i wouldnt worry about it but Im guessing you are seeing something of larger magnitude.

It could be that the LDO is unstable. Have you checked the ESR of your decoupling capacitor? Some LDOs are very fussy about that and the TLV2217 looks like one of them.

Also, what happens if there is a "dummy" program in the PIC i.e. one that does nothing, just goes round a loop? That should eliminate possible loading effects.


Thank you to all...

I have solved the problem which is that the decoulpling capacitor....

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