On Nov 24, 2017, at 23:15, Luke Kenneth Casson Leighton <[email protected]> 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. [.…] 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!" _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
