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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: UCC33420 dc/dc converter eval
Date: Thu, 10 Apr 2025 00:43:24 -0000 (UTC)
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john larkin <jl@glen--canyon.com> wrote:
> On Wed, 9 Apr 2025 23:45:23 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
>> john larkin <jl@glen--canyon.com> wrote:
>>> 
>>> 
>>> My TI rep was being difficult, so I just bought an eval board from
>>> Digikey for $100.
>>> 
>>> It makes a nice 4.993 volt output, but it's wicked noisy.
>>> 
>>> https://www.dropbox.com/scl/fo/8fybyu5l3w4tdgt1y0386/AFunYi9K15UgNpkQzEbYaVA?rlkey=j261b4ca5kc966vq2y03fw0md&dl=0
>>> 
>>> 53% efficient into that 0.25 watt load.
>>> 
>>> 
>> 
>> Yikes, what a piece of junk. Small maybe, but lots of parts needed for
>> cleanup. 
>> 
>> What does it do to the input rail?
>> 
>> Cheers 
>> 
>> Phil Hobbs 
> 
> I didn't scope the input rail. I expect it has lots of noise and DC
> load in bursts.
> 
> The architecture seems to be a simple forward converter with lots of
> step-up, and regulates bang-bang in inefficient bursts. I expect that
> if I reduced the input voltage, it woud get more efficient as the
> bursts approach 100% duty cycle and it starts to lose regulation.
> 
> I took the rig down. It won't work in my application, as a high side
> gate drive supply in a GaN half-bridge. Way too noisy.
> 
> I love the idea of a tiny cheap dc/dc converter on a chip, but not
> this one.
> 
> $100 for this eval board is silly too. It comes with a generic
> application brochure that says "go to the web site"
> 
> I now have, in theory, three TI support engineers, whose universal
> support is "go to the forums."

Enjoy it while it lasts. In six months they’ll be shoveling AI-generated
summaries of the forums. :(

> 
> I remember in the olden days when our TI guys would show up with a
> briefcase full of data books and unexpected new samples.

As I’ve said before, as a young teenager I had a subscription to the
Motorola Update.  For a *very* small fee, four times a year they sent me a
big box of databooks and app notes. 

It was magical stuff, most of which I understood dimly at best—bit slice
processors, TTL register files, MNOS nonvolatile memory, all sorts of
things. 

It made a big impression on my subsequent career. 

Cheers 

Phil Hobbs 



-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics