[gta02-core] LCM review

Álvaro Lopes alvieboy at alvie.com
Fri Jul 24 11:14:24 CEST 2009

Werner Almesberger wrote:
> Rene Harder wrote:
>> I also found that the capacitor C6005 in our drawing has the values
>> 100nF but is NC in the GTA02 and not existing in GTA01. Is there any
>> particular reason for this which I'm not aware of? Neither could I find
>> any ECN regarding this change.
> Looks like a bug, yes. C6005 has an interesting history. It was 47 pF
> in GTA02v5 and became NC in GTA02v6. From the GTA02 and GTA03 lists:
> Andy, 15 May 2008:  p7  C6005 should be 47p again?
> Allen, 19 May 2008:  No! I will remove it.
> Allen, 02 Jul 2008:  7.[...] and add C6004 and C6005
> Andy, 20 Aug 2008:
> | But, I recall there was talk about "destroy PMU" about C6005 six months
> | ago.  This was simply 47p on -ve side of LED.  Nobody explained why 47p
> | there can "destroy PMU".
> Maybe it would upset the feedback loop. In any case, we should make it
> NC, as in later GTA02 versions and GTA03-6410.

It might ressonate and become unstable (ie, oscillate). I have not done any calculations, but makes sense.

> - Werner
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