[Milkymist-devel] wrong connections on ADV7125 schematic ground pins
adam at sharism.cc
Thu Mar 17 22:21:05 PDT 2011
I just checked ML40X known issues:
*"2) ADV7125 Ground Pins *
On ML401, ML402, and ML403 boards, some of the ground pins of the Video DAC
(ADV7125 - U13) are connected to digital ground instead of analog ground
resulting in increased VGA video noise. Ground pins 1, 2, 14, 15, 39, and 40
of U13 should be connected to the analog ground (Pin 2 of FB6). "
Its sch. :
After confirmed that online newest adv 7125 datasheet that Figure. 10
Typical Connection Diagram:
a) Analog ground are shown clearly enough instead of our wrong connections
to digital grounds.
b) must be included all below to analog ground :
pins 27, 31, 33 of U18 group; pins 1, 2, 14, 15, 25, 26, 39, 40 of U18
group; ground of R144~R146; R142's ground; pins 6, 7, 8 of J17(VGA
connector); They are all related to "analog" power rail for DAC and
On analog device web there's a good doc of AN333: Design and Layout of a
Video Graphics System for Reduced EMI,
All contents inside this doc is good to reflash and remind us that we've
taken less considerations. It's bad that we all missed this significant
With regards to if this discovery influence audio performance, this is much
worthy to pay more experiments.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Devel