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'[PIC] 18F45J10 - causing a short on the board?'
2007\10\16@110038 by alan smith

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Has anyone used the 44 QFP package for this part?  This is one of those strange things thats going to turn out to be somthing else..but so far it points to the chip.  I have a 3.3V power to ground short, so I used a short sniffer to isolate the area, then started to isolate it further.  The short is measuring less than 4 ohms from power to ground.
 
 I lifted the two power pins on the chip and it cleared it up.  I've verified that the chip is down correctly, and that the power pins are connected correctly.  The one thing I forgot was the 10uF cap for the internal regulator, but that shouldnt cause a power to ground short.  This test is unpowered as well.  I did  power it up, but once I saw the supply was being dragged down I shut it off and did the check.  The fact that the cap wasn't there...could maybe have damaged the PIC?  

     
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2007\10\16@172216 by Spehro Pefhany

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Quoting alan smith <spam_OUTmicro_eng2TakeThisOuTspamyahoo.com>:

> Has anyone used the 44 QFP package for this part?  This is one of  
> those strange things thats going to turn out to be somthing  
> else..but so far it points to the chip.  I have a 3.3V power to  
> ground short, so I used a short sniffer to isolate the area, then  
> started to isolate it further.  The short is measuring less than 4  
> ohms from power to ground.
>
>   I lifted the two power pins on the chip and it cleared it up.    
> I've verified that the chip is down correctly, and that the power  
> pins are connected correctly.  The one thing I forgot was the 10uF  
> cap for the internal regulator, but that shouldnt cause a power to  
> ground short.  This test is unpowered as well.  I did  power it up,  
> but once I saw the supply was being dragged down I shut it off and  
> did the check.  The fact that the cap wasn't there...could maybe  
> have damaged the PIC?

More likely a difficult-to-see short such as a bit of solder behind
the pins that disappeared when you unsoldered them.

Best regards,
Spehro Pefhany




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