Re: tiny dc/dc

On Sat, 29 Mar 2025 16:30:23 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

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

On Fri, 28 Mar 2025 16:49:23 -0400 (EDT), Martin Rid
<martin_riddle@verison.net> wrote:
 

john larkin <jl@glen--canyon.com> Wrote in message:r

Check out UCC33420. It's a tiny cheap isolated dc/dc converter. It switches at 64 MHz!

 
Why does it have such poor esd ratings?
The ucc33421 is better, but not 15kv.
Cheers

 
Right now I dodn't need kilovolts of isolation. I want to make a GaN
totem-pole driver and want a floating power supply for the high side,
but I want very low switching noise for low jitter on the rising edge.
 
I might try one of these with a bunch of added filtering. It might be
better than some dc/dc that works in the 100 KHz sort of ballpark.
 
Or it might be much worse.

>
I bet the gain bandwidth of a GaN FET in its linear range at high current
is pretty impressive.
>
I’m using SiGe BJTs to speed up the edges of my TDR pulse generators.
Driven from a 500-ps comparator edge, it’s fast enough to oscillate on the
falling edge if the layout isn’t right.  That’ll make really entertaining
jitter.
>
Cheers ?
>
Phil Hobbs

One part that I like is the EPC2037, the tiny BGA thing. I think you
have used it too.

Transconductance is about 1.5S and it's on hard by 3 volts on the
gate. Capacitances are absurdly low compared to a silicon mosfet...
reverse transfer is 0.1 pF.

But a little noise on the gate drive will surely jitter the output.

I never had much luck getting bipolars to make fast output edges, but
I haven't tried SiGe.

That tiny EPC thing is rated for 100 volts and can conduct 2 amps!