[SI-LIST] Re: PLL Loop filter
- From: "David Greig" <David@xxxxxxxxxxxxxx>
- To: <bvg@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 7 Sep 2004 17:29:07 +0100
Hi Girish
I would hazard a guess that the filter cap is ceramic, and another guess
that it is surface mounted in a mechanically unsupported area of the board.
Most ceramics exhibit a piezoelectric effect. The value will also alter on
board deflection, in the order of 0.1% to 0.5% of value in the extreme
(before popping off!).
Film caps do not have a piezoelectric effect.
Best Regards
David Greig
_________________________________________
Director
GigaDyne Ltd
Buchan House
Carnegie Campus
Dunfermline KY11 8PL
United Kingdom
Tel. +44 (0) 1383 62 49 75
_________________________________________
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Girish Bangalore
Sent: 07 September 2004 17:04
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PLL Loop filter
Hello Friends,
I need some help in my analysis of a problem listed below,
I am working on a product for a graphic application using an ADC with a
built-in PLL (clock for digitization of Video). During a vibration test on
the board we found out that the image shakes and we fixed everything we
suspected from loose cable to loose components with no success. Finally,
based on some expert advise.. I was told that the problem could be caused
due to mechanical stress on the loop filter capacitor which may be causing
the capacitance to change during vibration and thereby disrupting the PLL.
Has anyone faced similar issues? I would appreciate your expert feedback.
Thanks,
Girish
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