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July 2009

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Subject:
From:
Toby Carrier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Toby Carrier <[log in to unmask]>
Date:
Fri, 17 Jul 2009 17:31:44 -0400
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text/plain (97 lines)
Lee,

	The op-amp was originally installed to help a differential video
driver with ESD. The driver was casing the output video to get very snowy
with an ESD discharge to chassis or common ground. The op-amp helped in
passing the ESD failure, so, the original issue was "a". But when a new
board spin was done, the QSOP package was what was designed in. But, the
QSOP package didn't help a bit, it was like it was not even there. But, if
the SOIC package was once again kludged in, we would pass the ESD events.
But at no time did we ever damage a part. We have since found a fix, but
want to know what the difference between the packages could be.

Toby

-----Original Message-----
From: Lee Hill [mailto:[log in to unmask]] 
Sent: Friday, July 17, 2009 4:58 PM
To: 'TechNet E-Mail Forum'; 'Toby Carrier'
Subject: RE: [TN] ESD failure difference between 16-QSOP and 16-SOIC Video
Buffer

Hi Toby:

1) Does "failure" mean a) "stops working but will come back to life with
power and/or software reset" or does it mean b) "damaged"?

2) Is this a system-level test?

If it is a system-level test and 1a is true, then you have a gross system
level problem such as non-repeatable shielding performance of chassis,
poorly connected video cable, screws or conductive gaskets left out, etc.

Less likely - perhaps inconsistent operator test method - air discharge ESD
has been extensively researched and has many uncontrolled parameters which
leads to poor repeatability from test to test. But 1kV versus 25kV is so
huge a spread you would really have to be trying to mess up on purpose :-)

Best Regards

Lee

 
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Toby Carrier
Sent: Friday, July 17, 2009 1:51 PM
To: [log in to unmask]
Subject: [TN] ESD failure difference between 16-QSOP and 16-SOIC Video
Buffer

Hi,

Does anyone have an idea why a 16-SOIC Video buffer would pass ESD 
testing with being kludged in, compared to a 16-QSOP package of the same 
part actually soldered to the PCB? The SOIC part passes a Chassis and 
Common ground Air Gap event up to 25kV, but the QSOP part has failures on 
both chassis and common at 1kV and less? I would appreciate any articles or 
explanations that you might have.

Thanks

Toby Carrier
Engineering Technician

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