Cap C-V test...

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[john larkin]

On Thu, 01 May 2025 13:09:50 -0700, john larkin <jl@glen--canyon.com>
wrote:

https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1


The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I\'ll add another cap in parallel.

My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.

Here\'s part of what I\'m doing.

https://www.dropbox.com/scl/fi/ol237j24h1c4e4ti760bn/P978_A15.pdf?rlkey=amzd3xwy074mcakvzudva4ryi&dl=0


We\'re designing a couple of products (one dummy load, one power
supply, both 8 isolated channels) and each board needs 8 isolated
20-watt power supplies. So we have 8 full bridges each pumping a 500
KHz square wave into a transformer-rectifier.

All share the +48 supply. If we polyphase the square wave drives, the
ripple currents will kinda cancel and the channels all share their
2.2u caps. I think.