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From: Klaus Kragelund <klauskvik@hotmail.com>
Newsgroups: sci.electronics.design
Subject: Re: tiny dc/dc
Date: Sat, 5 Apr 2025 01:48:34 +0200
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On 05-04-2025 00:22, john larkin wrote:
> On Fri, 4 Apr 2025 23:48:53 +0200, Klaus Kragelund
> <klauskvik@hotmail.com> wrote:
> 
>> On 31-03-2025 01:37, john larkin wrote:
>>> On 30 Mar 2025 21:43:28 GMT, Uwe Bonnes
>>> <bon@hertz.ikp.physik.tu-darmstadt.de> wrote:
>>>
>>>> john larkin <jl@glen--canyon.com> wrote:
>>>>> Check out UCC33420.
>>>>>
>>>>> It's a tiny cheap isolated dc/dc converter. It switches at 64 MHz!
>>>>>
>>>>
>>>> I guess Murata NXJ switches at a similar frequency!
>>>
>>> About 100 KHz.
>>>
>>> https://www.dropbox.com/scl/fo/w90gg474w9h0wsqkbpd9e/AC8Oh-LB9La9PcvIGGOYWtg?rlkey=agwx067u5vk6z04ir2ktp4dy0&dl=0
>>>
>> That vertical relative to the PCB winding structure is really nice.
>> Solved problems with clearances.
>>
>> If only I could have a PCB manufactorer do that, but maybe it's out there.
>>
>> Murata is 3.11mm PCB. Could be done with 2 1.6mm PCBs, and pocket
>> milling, turned over, plopping in a ferrite, glue, and solder.
>>
>> But, do they make the vias after the ferrite has been sandwiched?
> 
> Seems to me that they have to. It's an ordinary PCB fab process,
> except there's that ferrite inside the board first.
> 
> The vent hole on the side is interesting. Why not squirt in ferrite
> paste, or 3D print the core?
> 
> There are several people now who are integrating the isolation
> transformer into a single IC somehow.
> 

That can be done with the oxide layer, like for optos. The distance from 
the emitter to reciever LED is very small, but handled by the oxide 
layer that is approved for 20++ years lifetime for double insulation

AFAICR, the oxide layer is in the order of 10um, approved for +5kV isolation

For the icouplers, it means they can make a transformer with quite good 
coupling factor