[SI-LIST] Re: PLL Loop filter

  • From: steve weir <weirsp@xxxxxxxxxx>
  • To: David@xxxxxxxxxxxxxx, <bvg@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 07 Sep 2004 10:09:01 -0700

David, it is amazing the problems one can solve with a router bit.

Steve.
At 05:29 PM 9/7/2004 +0100, David Greig wrote:
>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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