Common step-down switching regulator

I like the National Semi LM2575T series (TO-220 package). Easy to use, comes in fixed and adjustable varieties, readily available. Low frequency switcher.

But there may be better choices out there

"pimpom" schreef in bericht news:hd1ohb$l0r$ snipped-for-privacy@news.albasani.net...

Last time I needed such a thing I found the MC34063. Looks like to fit your requirements pretty well.

petrus bitbyter

Most ubiquitous and ridiculously cheap MC34063A and copies, but it is looking a bit long in the tooth. It's slow and transistor output. So you will need larger inductors and capacitors, and dissapate more heat, than more modern devices.

It is frustrating that there don't seem to be any newer parts anywhere near the price.

Thanks. I'd already looked at the LM25575 but the external component count is a bit more than I'd like, though it seems to have regulation and efficiency than the LM2575. I think I've seen the 2575 used more than once before, but a browse of the NatSem site didn't bring it up immediately, so it didn't come to mind until you suggested it. Looks like it will do nicely. Thanks again.

Thanks. I'd already saved the datasheet of the MC34063. If it's widely available, it's a good candidate.

Thanks. By transistor output, I take it you mean bipolar. The datasheet I have of the MC34063A is by ON Semi. It gives only a limited amount of info about the efficiency and dissipation. Maybe I should download one from another manufacturer.

LM2672 is cute, 1 amp in an SO-8, 260 KHz.

Lately we've been using a lot of LTM8023s, which is a switcher with internal Ls and Cs and everything. A bit expensive, but very simple and very clean. It's sort of a BGA package.

John

If you have that kind of requirement, there are definitely some offshore-only parts that are probably near the price (probably lower maximum input voltage). Try tearing apart some consumer goods. Also some of the NS switchers have been cloned.

John (or anyone else here), have you looked at the RECOM R-78 series "TO220-style" integrated switchers? They won't fit a "low cost" category of course. I'd be very interested in comments from anyone who has used them. (I have eyed them off for a project in the past but wound up laying out an MC34063 solution.)

I'm using an NCP3063 which is a higher speed upgrade on a current project. It's useful where you need buck or boost.

My unit has low power 5V buck and a 24V boost to power the sepic circuitry as well as USB charger outputs. All bult around the NCP

I've used that one too and you're right. Still only 150kHz and bipolar though. Might be a good fit for the OP.

It's cute all right, but not as cheap as I'd like it to be.

That's real neat but, as you say, way too expensive for the kind of use I have in mind. It's certainly worth keeping in mind for other purposes where price is not an important factor.

The NCP3063 looks like a good trade-off between price and performance, and the boost option is attracttive. Perhaps a mixed stock of it and the MC34063 will be a good idea.

The R-78 series would be perfect (~95% efficiency, through-hole option, no external parts except the inevitable input-output caps) but I couldn't find indicative prices with a quick search. I expect they'll be a bit on the high side for my purpose and also not easily available everywhere.

Thanks for all the replies, everyone. They were all on-topic and really helpful - something that's all too often *not* the case on Usenet.

I particularly appreciate your keeping in mind the criteria of low cost and easy availability. The latter is necessitated by my location and work environment (I won't bore you with the details) which is why I didn't just make a selection from the results of my own searches. I hope you won't mind if I ask the same type of questions about other devices from time to time.

(snip)

The price I obtained here in Oz for the 5V 1A beast was ~$A13 in singles. As pcb real estate was available I went 34063, which gave a cheaper result.