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

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sat Jan 6 04:50:19 GMT 2018

crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

On Fri, Jan 5, 2018 at 4:02 PM, Richard Wilbur <richard.wilbur at gmail.com> wrote:
> On Fri, Jan 5, 2018 at 4:05 AM, Luke Kenneth Casson Leighton
> <lkcl at lkcl.net> wrote:
>> On Fri, Jan 5, 2018 at 8:27 AM, Richard Wilbur <richard.wilbur at gmail.com> wrote:
>>> On Fri, Jan 5, 2018 at 1:00 AM, Luke Kenneth Casson Leighton
>>> <lkcl at lkcl.net> wrote:
>>>>  rectangular all-layers keepout, showing 1 and 3 here... damn layers 2
>>>> and 5 have a weird shape (not enough clearance auto-generated) let me
>>>> make it an oval all-layers keepout instead...
>>> Those do look very nice, indeed!
>>  did the trick.  pain doing them by hand, had to do the flood-fill,
>> then adjust the keepout, then write down by hand the distances that
>> the keepout fitted cleanly to the edges, _then_ throw that file away,
>> _then_ go back and put the rectangle left-right... bletch :)
>>  anyway i moved the PWM via up a bit, left the 3V3 VIAs where they
>> were - sorted.
> The results are great!  Thanks for all the hard work to make it happen.

 yeah you too.  dang it's been a while :)

> So I'm happy with the layout of the HDMI!


> I checked for vias in component pads (manufacturability issue) and
> since the gerber viewer I'm using complains about all the tools in the
> drill file when I load it, I can't see the via holes.  So there may be
> several false alarms in this list.  Could even be mostly false alarms.

 it's not.  basically the trick has been, due to cramped space, to put
at least 2 VIAs around power decoupling capacitors (not done by me),
and they're just on the edge.  space is pretty crowded and all
previous boards worked fine (and there's been a *lot* of
pre-production boards now).

> But I would definitely check out C3 on layer 1 as there seems to be a
> via in the middle of one of the pads.  (Marked with red arrow in
> attached picture.)

 yehyeh good call that one was me, i had to reorganise the nearby
(East) power capacitors, and shuffle (West) the components next door,
in order to fit two (horizontal) 0603 4.7uF where there was previously
one (vertical) 0805 10uF.

 shuffled that VIA up as there's plenty of space.

 iiii think we're good.

 now the only concern is, blasted frickin apple, has sucked world-wide
demand not just for the entire supply of 0.1 10 and 100uF capacitors
but f*****g DDR3 and eMMC *as well*.

 i now have to be extremely careful on selecting the right DDR3 RAM
ICs... *sigh*.


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