My first switcher

The CUI and Murata and Recom dc/dc bricks seem to be fine. But don't believe their short-circuit specs unless you verify them yourself, and then still don't believe them if you can help it.

The CUI PDS1 parts are really cool. Isolated +- output. I use them even when I don't need the isolation.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

We use a lot of LTM8023, which is a brick that includes the switcher, inductor, and caps. It's not cheap, but it's convenient and very quiet. It can do step-down buck or pos-to-neg conversion.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Yeah, have to be careful with the ones that are basically just choppers, there's no current limiting or protection or anything. Short it for a second or two and poof, out oozes a teensy bit of magic smoke, in condensed form... if you're even that lucky.

The bigger ones (3W+?) I think tend to be proper current mode controllers, and say they're fine to short forever.

Tim

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Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com

One part saye infinite short duration somewhere on the data sheet, and

8 hours somewhere else.

One CUI part, VASD1, claims 1 second short withstand, but it blows up in under 100 ms. I added an LM317L ahead of it as a current limiter.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

No not async.. the first thing I do is sync up the start pulse with the clock. But I hardly do any digital things.... (The last was ~1995 pulse programmer for an NMR.. LS ttl.)

Anyway I'll start a thread on SEB. I think most here would suggest throwing a uC at the problem.

later, George H.

Re: OT... Not at all Jeroen, I'll post my hairball and problem over on S.E.Basics, and if you have comments (or just want to laugh at it) then I'd enjoy that.

George H.

Thanks Tim... I think the LM2594 is the IC Phil H. likes also. I looked at that too. ON semi makes one that looks more versatile than the TI version.

(nice spec sheet too!) I should order some for "play" time. But unless the noise is horrible it hard to beat the potted CUI part that I found. $4-7, two ceramic caps and it goes both ways. I could use those in other things too. (maybe hang a cap multiplier on the output.. three more parts.)

George H.

3)

John Larkin is unwilling to use transformers that he can't buy off the shel f from a broad-line distributor.

There's always a transformer winding shop nearby, and you can buy a range o f ferrite cores and matching formers from broad-line distributors. It's not rocket science, but your friendly local winding shop will know a lot more about the subject than you will. If you can live with that - and John Larki n obviously finds it difficult - getting small batches of special purpose t ransformers wound is pretty straight-forward.

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Bill Sloman, Sydney