On Nov 24, 2017, at 23:15, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
Thank you for the picture.
ok so this shows what's going on: already those GND vias have been moved significantly away from the pads associated with them (the ones for the 5V0) and those are MAJOR power (2A) so it's really rather important to have them close.
Agreed!
now, what i _could_ do is turn the one connected to IPSOUT round by 90 degrees (anti-clockwise) and move it upwards, making use of the GND vias near the HX2P/N diff-pair vias. then there would be room to do the same thing with the 5V0 power in one as well.
Sounds good.
one thing: in speaking with mike from the factory, he's been tracking the price of capacitors now, which have showed a FIVE TIMES increase in price over the past six months. 0.1uF, 10uF and 100uF capacitors in particular, the prices have gone INSANE.
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Sorry about the demand fluctuation creating such huge price fluctuations.
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. If you have the room, both of these can be combatted by doing just what you have described!
bottom line: if i shuffle in two 0603 4.7uF caps as a replacement for the 0805 10uF, it reduces the cost on the BOM based on current pricing, improves power stability, and also means that those VIAs in the middle there can entirely be removed.
Excellent solution to both problems! Id est, "Good show, mate!"