The problem when we try to program the PIC is that there is too much current draw when supplying 3.3V to the Vdd lines (on the order of 1 Amp). We burnt out a chip once doing that (it made a smell and got crazy hot) and so we've been trying to do it again, but this time limiting the current to about .1A. However, when we do this, we only are able to supply 1.1V to the pic since our power supply is limiting the current. We have done a continuity test and get about 518 ohms of resistance (so no shorts), however for some reason there is still too much current being drawn. I am unsure how to fix this. Any advice would be helpful. Also if anybody has any general tips for how to program a pic that would be great, specifically any pitfalls that many people fall into when trying to hook everything up, but aren't obvious pitfalls.
Is this normal behavior?
TWhen you say check for shorts, do you mean to check for resistance between each pair of Vdd/Vss pins?
Yes, exactly. Look for a low resistance path between them, from your description it is the most probably cause of the large current measurements.
With the bare minimum connections shown in your schematics, the normal current draw should be considerably less 100mA at 3.3V.
The specification from the datasheet: 0.6 mA/MHz Dynamic Current (typical).
BigDog
These are the resistances we got between each of the pairs of Vdd/Vss (with correct polarity at each)
pins 9 & 10 (Vss/Vdd) = .1 mOhms
pins 19 & 20 (Avdd/Avss) = 47 kOhms
pins 25 & 26 (Vss/Vdd) = 48 kOhms
pins 38 & 41 (Vdd/Vss) = 104 mOhms
pins 56 & 57 (Vcap with no capacitor, Vdd) = 47 mOhms
We did what you said, where we ramp up the voltage with a single pair of Vdd/Vss pins (with new capacitors) and weren't able to bring the voltage higher than around 1 Volt with .1A
Here are the results of the continuity test for each pin pair (this is what the multimeter said)
pins 9 & 10 (Vss/Vdd) = 737 ohms
pins 19 & 20 (Avdd/Avss) = 1000 ohms
pins 25 & 26 (Vss/Vdd) = 737 ohms
pins 38 & 41 (Vdd/Vss) = Open
pins 56 & 57 (Vcap with no capacitor, Vdd) = Open
So we were off by one on all our connections and didn't have the back plates connected to ground. We are going to try it out soon. Hopefully we didn't mess up the chip. Can't believe we didn't notice this
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