Re: UCC33420 dc/dc converter eval

john larkin <jl@glen--canyon.com> wrote:

On 10 Apr 2025 08:48:48 GMT, Uwe Bonnes
<bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
...

I think this high frequency noise should be easy to filter by some CLC
Filter.

 
Not really. I need it to be close to the load, and that load is super
noise sensitive. I didn't check, but there is no doubt some
considerable and nasty emitted mag fields too.
>

Of course, the vincinity of any isolated DCDC is super noisy. If
nothing else helps, think about battery power.

 
In addition to all the high frequency crud, there's the basic burst
and its side effects in the hundreds of KHz range, would would take
giant parts to filter.

Look at LDOs with good PSRR at high frequency. From the datasheet, the
TPS7A20XX is still in the 40 db range at 1 MHZ. The LT1963 may be
better, but is much more expensive, the TPS7A20 is rather cheap and
available.

There are interesting parts around now that include their own power
isolation. Some are capacitive, not inductive, so may be better.
 

What part do you expect to have capacitive power transport? Capacitive
signaling is however common.

B.t.w, looking at a ISOW7841, I also see frequency in the 50 Mhz
range.

Wuerth WPME-CDIP Capacitive Digital Isolator Powered talks about 13 MHz

--
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de

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