Electronics > Projects, Designs, and Technical Stuff

5v PSU Spiky issue

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johnnyfp:
Hi,

I've got a 5v switchmode PSU based on a MCP16322 and it's not outputting a very clean supply.

I've tried various options (increasing Electro cap, adding extra Ceramic cap to react faster etc) but would like your (sensible) opinion as to what is the cause of the spikes.

cheers

madires:
Please try a ripple filter, an inductor of about 10-33µH and a cap around 100-220µF

Nerull:
Many switching PSUs need some load for the feedback circuit to work properly, are you accounting for that if needed?

johnnyfp:
Yeah I've put a 8ohm resistor on the line. Nice and toasty.

So Madires, the LC filter seems to have done the trick. I didn't have 33uH in stock, Tried with 68uH and a 220uF Cap.

What gets me is why the recommended design out of the datasheet is so flawed!

The other concern now is the amperage through the inductor.

minime72706:
How much current are you pushing through that 8ohm load?

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