Re: UCC33420 dc/dc converter eval

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