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Help selecting components for MAX641

Discussion in 'Electronic Design' started by Simon, Aug 21, 2004.

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  1. Simon

    Simon Guest

    I am planning on using a Max641 step-up converter. However as a
    beginner, I am finding it difficult to choose the external components
    - have studied Maxim's data sheet, but still a bit confused about what
    Mosfet, inductor and capacitors to go for.
    Can anyone make any suggestions. The 5V output will be 1A maximum
    current and as well as the rest of the circuit, needs to power a PIC
    mcu (does that mean I need to be concerned with the
    smoothness/ripple)?
    If you need any more information about the requirements, please ask.

    As I said, I am a beginner and that includes soldering skills, so
    preferable parts that are not too miniature (surface mount is OK but I
    have trouble with the really tiny ones). And I would hope to be able
    to use parts that are readily available from RS or Farnell in Europe.

    Thanks in advance for any help.

    p.s. Alternatively if anyone has an alternative suggestion than the
    Max641, I would be interested to hear - it will use 2xNiMH 1.2V AA
    equivalent batteries, and as I said above, should provide 5V, 1A
    output. With minimum external part count, not too miniature and as
    efficient as possible.
     
  2. James Meyer

    James Meyer Guest

    Go to Linear Technologies web site and look at the products there. Then
    get a free copy of their software, switcher cad, to play with. The cad program
    will let you construct (simulate) any of their chips along with real-world
    components that you can buy.

    Jim
     
  3. Fred Bloggs

    Fred Bloggs Guest

    Instead of shooting your pig mouth off with a bunch hot air
    generalizations, why don't you do that and walk the OP though a design,
    posting your simulation resluts [sic] to abse....
     
  4. Oh-oh! Someone's run out of their meds again!
     
  5. John Fields

    John Fields Guest

     
  6. Water off a duck's back, old boy; water off a duck's back. ;-)
     
  7. James Meyer

    James Meyer Guest

    Generally when someone goes to the effort of posting a well thought out
    reply that contains explicit recommendations, the original requestor will come
    back with some reason why none of the information is of use to him and tell us
    that he will continue to pursue his original direction no matter how likely it
    appears to us to be fruitless. (Burridge syndrome)

    I'd rather offer a quick look at a different direction and then, if the
    original requestor shows some interest or needs more details, provide a
    follow-up.

    You, on the other hand, tend to make pronouncements from on high and
    expect the whole world to fall down at your feet, believe every word, and kiss
    your ass for even bothering to speak to them.

    That just ain't my style, Clyde.

    Jim
     
  8. Fred Bloggs

    Fred Bloggs Guest

    You only read it that way because you they released you from treatment
    too early. See a lawyer about suing your psychiatrist.
     
  9. You ain't got no style, C**t. FOAD.
     
  10. Ken Smith

    Ken Smith Guest

    Perhaps the Max641 is above the beginner skill level. There are switcher
    chips where the power transistor is built in. I'd suggest you look at
    these because in general they are easier to work with.

    If you are using the MAX641, it looks like you need a fairly large
    (mechanically) 50uH (or so) inductor.

    I'd suggest against using this chip because it doesn't have a current
    limit. This means that unless you add your own somehow, one brief short
    will destroy the circuit.
    Could you live with an unregulated 4xNiMH supply?
     
  11. James Meyer

    James Meyer Guest

    "... you they released you ..."?

    Take a nap, Fred. You're blithering.

    Jim
     
  12. Bob Wilson

    Bob Wilson Guest



    Ahh yes. SwitcherCad. AKA "Switchmode Power Supplies for Dummies". You too can
    design a SMPS without understanding anything about it! :)\

    Bob.
     
  13. Steady on, Bodge. LTSpice is my favourite toy atm.
     
  14. Fred Bloggs

    Fred Bloggs Guest

    Even that is not enough assist for some people...now you have all sorts
    of dummies like the "bit heads" thinking they can do this on their own.
     
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