Silent Switcher - LT8640s meets KiCad

RE: Silent Switcher - LT8640s meets KiCad

shabaz — Tue, 01 Oct 2024 19:15:05 GMT

Nice project! And great to see the TO3 footprint, that shape brings back many memories : )

I struggled to measure the noise from a transformer-based power supply, interestingly, even with a biscuit-tin enclosure, with the MXO 4, it was sensitive enough that there was noise around 11 MHz that I couldn't explain... and it was getting in through the coax (even though it was double-shielded RG316 coax). I had to swap out to semi-rigid coax to get rid of that noise. I used a 10 nF DC blocking capacitor (since I was interested in looking beyond a few hundred kHz), which is the red block visible connected to the yellow/black wires in the centre of the photo.

Afterwards, I was thinking, maybe it would be good to have a little adapter with a DC-blocking capacitor, and a zener clamp perhaps, and then decent shielded cable, in a metal Hammond box for instance, so that it can be attached via semi-rigid coax to the biscuit tin, and then connected to a 'scope or even an ADC (e.g. Digilent MCC172, or an audio card).

RE: Silent Switcher - LT8640s meets KiCad

Jan Cumps — Tue, 01 Oct 2024 19:08:37 GMT

"I don’t think the LT8640 is making these, but more work is required to be sure."

Did you bring anything new to your lab lately? LED lighting? A new mobile phone (charger)?

RE: Silent Switcher - LT8640s meets KiCad

jc2048 — Mon, 30 Sep 2024 15:05:00 GMT

Interesting blog. I really must have a go with KiCAD and see how I get on with it.

"Looking with a slower time base shows the nose envelope with some very unexplained modulation at low 10s of kHz frequencies – looks a bit like AM radio !"

Would that be a side effect of the spread-spectrum clock?

Although the spread spectrum clock will be simply frequency modulated, the cycle time will then be varying and that will interact with the ramping of the inductor current and translate back to a voltage with the ESR of the output caps. So you might then see a small amount of AM modulation on the output. Does that sound plausible?

RE: Silent Switcher - LT8640s meets KiCad

dougw — Mon, 30 Sep 2024 13:47:28 GMT

Cute idea for a TO3 card...