Re: Processor wirh Vdd-Vss Short

>> Hi All, >> >> I had a tray of 3v processors back from the boad loader and 20 of about >> 80 had a dead short between Vdd and Vss (3ohms). >> >> Any idea of what could of caused it? >> >> ESD? >> >> Board loader improper handling? >> >> Vdd Transient on power? >> >> Any ideas and experinces you have to share would be apprecicated >> >> Joe > > Counterfeit part? > > -- > Tim Wescott > Control systems and communications consulting >
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> > Need to learn how to apply control theory in your embedded system? > "Applied Control Theory for Embedded Systems" by Tim Wescott > Elsevier/Newnes,
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Hi Tim,

I had consider this but - Source has been identified from official distributor of the micro and ins a seal vacum pack.

Joe

Reply to
Joe G (Home)
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Hi scott,

3ohms was the max resistance measured a few were 1 ohm - both polarities.

I used the term "dead short" loosely as the meter accuracy is _+ 1ohm - also allowing for lead resistance.

Joe

Reply to
Joe G (Home)

Hey Jim,

Thanks for your input,

Boards come back from board loader - first power up the the 3v regulator starts to shut down (~ 100mA)

V/I curve ===> good idea

I wish I had one of those good USB microscopes!

Regards Joe

Reply to
Joe G (Home)

So how do you know it is the processor, and not a solder or etching bridge ? Drop the supply a little, so things do not fry, and you can do a voltage profile along the traces with a millivoltmeter. That shows where the current is actually going, before you remove anything. It can help find errant 'shorts'. These boards were bare-board tested ?

Check the package markings carefully - it is the package detents that matter, not the direction of the brand markings.

-jg

Reply to
Jim Granville

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