[Arm-netbook] HDMI High-Frequency Layout: Recommendations

Luke Kenneth Casson Leighton lkcl at lkcl.net
Wed Jan 17 11:41:03 GMT 2018

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On Tue, Jan 16, 2018 at 9:06 PM, Richard Wilbur
<richard.wilbur at gmail.com> wrote:

>> The goal is to avoid unnecessarily impeding this return current path.
>> I'm trying to avoid making the path >~200mil and putting any major
>> obstruction (like a huge layer void) in the way.
> While browsing the A20 datasheet, I found that the HDMI section does
> have a power pin but not labelled the way I was asking you about.

 ah ok

> Page 18 mentions that VCC-HDMI is a power pin on ball #T13.  On the
> schematic it is connected to net HVP which has power decoupling
> capacitor C108 which looks like "104" => 0.1uF.

 yep.  and a VIA to the other side (BOTTOM) C108 is about as close as
you can possibly get

> Looks like the path from the copper on layer 2 below the HDMI pins
> (balls #TUVW 22,23) on the SoC (processor) to the VCC-HDMI power pin
> (#T13) is ~300mil.  It doesn't look overly impeded.

 yehh it seems to work fine, on this design and on other boards.


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