[Arm-netbook] HDMI High-Frequency Layout: Recommendations Vias Moveable?

[Luke Kenneth Casson Leighton]

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


On Sat, Nov 25, 2017 at 3:05 PM, Richard Wilbur
<richard.wilbur at gmail.com> wrote:
> On Nov 24, 2017, at 23:15, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> Sorry about the demand fluctuation creating such huge price fluctuations.

 maaad.  also the pricing on the DDR3 RAM IC is going nuts, but that's
for different reasons: it's getting "old" so not so common any more.
i'll need to test some 1866mhz DDR3 RAM ICs, but try them at the
350mhz speed that the layout copes with (safely, and with less power
used), see how it goes.


>> so in the meantime what i think i will do is, put in double batches of
>> *smaller* capacitors, with unusual values (three 33uF instead of one
>> 100uF), which is, from what i've read, a better way to ensure stable
>> power *anyway*.
>>
>> as in, two 4.7uF capacitors stabilise power much better than one 10uF
>> capacitor because of the increased current capacity of two caps -
>> something like that, anyway.
>
> Great idea!  You are correct in that the real capacitor which we can mount on a circuit board has an equivalent circuit which includes other components to the impedance besides just capacitance.  Namely ESR (Equivalent Series Resistance) and inductance.  The parasitic resistance dominates low-frequency response while the parasitic inductance dominates high-frequency response.  f you have the room, both of these can be combatted by doing just what you have described!

 :)