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

[Richard Wilbur]

On Jan 5, 2018, at 21:50, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
>> 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:
> 
> 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).

In that case, no problem.

>> 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.

Well I'm glad I looked and you had chance to fix it!

> 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*.

So the situation is the chips at the speed you designed for are much more expensive while faster ones are cheaper?  So the trick is how to choose a faster chip and integrate successfully into a system running at lower speed than it is specified for?