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Common step-down switching regulator

Discussion in 'Electronic Design' started by pimpom, Nov 6, 2009.

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  1. pimpom

    pimpom Guest

    Can you please suggest one or more ICs for general use as a
    step-down switching voltage regulator? This is for general stock
    to be used as needed for a variety of projects. There's a
    plethora of such devices out there, but what I'm looking for is a
    type that has become popular enough to be regarded almost as an
    industry standard and be available anywhere (and at a low price),
    in much the same way as the linear 78xx series and the LM317.
    Desireable specs would be -

    1. Low external component count
    2. Max input voltage around 40V
    3. Max load current 1A or more
    4. Fixed or adjustable output voltage
    5. Output voltage range 5-15V or wider
    6. Non-SMD if possible, but not essential
     
  2. Last time I needed such a thing I found the MC34063. Looks like to fit your
    requirements pretty well.

    petrus bitbyter
     
  3. 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.
     
  4. pimpom

    pimpom Guest

    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.
     
  5. pimpom

    pimpom Guest

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

    pimpom Guest

    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.
     
  7. 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.
     
  8. 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
    3063. The MC34063 wasn't good enough on the first prototypes.
     
  9. I've used that one too and you're right. Still only 150kHz and bipolar
    though. Might be a good fit for the OP.
     
  10. pimpom

    pimpom Guest

    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.
     
  11. pimpom

    pimpom Guest

    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.
     
  12. pimpom

    pimpom Guest

    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.
     
  13. pimpom

    pimpom Guest

    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.
     
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