18f4220 Chip gets hot !

[2camjohn]

Hio Guys,

Ive just moved to the 18f4220 and i have encountered a seemingly very basic problem ive never had before.


When I connect VSS VDD and VPP from my powered ICD2 development board, to the VSS, VDD and VPP pins on the 18f4220 (6,30,31,7,29,18), the chip gets very hot and the device ID reads 00.

The target board has just the chip and the programming socket on it, so I know there are no shorts or possible problems with the other components. The ICD2 works great with other chips.

Any help getting me past this point would be greatly appreciated.

Many thanks in advance,
John

 

[Nigel Goodwin]

You've connected the chip the wrong way round!, or to the wrong pins!

 

[2camjohn]

Thanks Nigel,

I guess im gonna have to break out the old jumper wires and breadboard.



The strange thing is, it only starts to get hot once I connect VPP. Ive checked and double checked the pin diagrams in the datasheet ad nauseum, every time it comes up right.

 

[2camjohn]

Nigel you were right there was an error in the pins I was connecting to.

It was odd because the problem only showed symptoms when VPP was connected, so I was drawn to that...


Anyway, I can grind a couple of pins off the chip and it should work.

This may be a really stupid question, but on PIC chips such as this one, where there are mutliple VDD/VSS pins, do I have to connect them all?


Cheers
John

 

[Nigel Goodwin]

You have to connect them to RUN the chip, I'm not sure about programming them - perhaps the datasheet might tell you?, but you may as well just connect them for programming anyway?.

 

[justDIY]

Anyway, I can grind a couple of pins off the chip and it should work.

what pins need "grinding off"?