Current controlled DC-DC converter: LT1339? >>HELP<<

Discussion in 'Electronic Repair' started by Davide Fabri, Feb 5, 2004.

  1. Davide Fabri

    Davide Fabri Guest

    Hello
    I am trying to design a 48Vin-30Vout-10Aout current-limited
    (programmable from microprocessor) step-down DC-DC converter.
    To do this I am looking for a current mode synchronous buck
    controller. The only one I found is a Linear LT1339: it can
    easily handle voltages up to 60V and directly drive the two
    mosfets. Nevertheless it has some drawbacks: mainly it is
    not born to be current-programmable, therefore I am not sure
    I will be able to set the current limit from the micro; then
    it needs 12V to be supplied; and finally it seems to be quite
    old and very expensive (about 7$ + vat !!).
    Can anyone confirm this is a good choice anyway? ...or maybe
    suggest me an effective alternative? Perhaps a lower voltage
    IC connected to an high voltage mos-driver (like a IRF2110
    from International Rectifier)?

    Thanks everybody for supporting.
    Davide


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    Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
    Davide Fabri, Feb 5, 2004
    #1
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  2. Davide Fabri

    Tim Wescott Guest

    Or, since you've jumped into the microprocessor camp anyway, how about
    sampling voltage and current with the microprocessor and generating the PWM
    directly from the microprocessor? Or if that makes you uncomfortable how
    about setting the voltage command to the converter from the microprocessor
    and servoing current in software?

    "Davide Fabri" <> wrote in message
    news:...
    > Hello
    > I am trying to design a 48Vin-30Vout-10Aout current-limited
    > (programmable from microprocessor) step-down DC-DC converter.
    > To do this I am looking for a current mode synchronous buck
    > controller. The only one I found is a Linear LT1339: it can
    > easily handle voltages up to 60V and directly drive the two
    > mosfets. Nevertheless it has some drawbacks: mainly it is
    > not born to be current-programmable, therefore I am not sure
    > I will be able to set the current limit from the micro; then
    > it needs 12V to be supplied; and finally it seems to be quite
    > old and very expensive (about 7$ + vat !!).
    > Can anyone confirm this is a good choice anyway? ...or maybe
    > suggest me an effective alternative? Perhaps a lower voltage
    > IC connected to an high voltage mos-driver (like a IRF2110
    > from International Rectifier)?
    >
    > Thanks everybody for supporting.
    > Davide
    >
    >
    > --
    > Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
    Tim Wescott, Feb 5, 2004
    #2
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  3. Davide Fabri

    Davide Fabri Guest

    Hello Tim
    the microprocessor has a 14kHz maximum PWM frequency, taht is not high
    enough to avoid bulky inductors for 10A output current: that's why
    I need an integrated switcher, that moreover has the advantage of
    integrating the mos drivers.
    Setting the voltage command for to the switcher from the microprocessor
    and servoing current in software is exactly what I would do: the problem
    is that I cannot use the voltage reference command to servo the current
    because the voltage loop is closed inside the switcher: playing with
    the Vref to set the current I guess it is not much sane.
    Hence I must act on another input of the LT1339 with another command
    (Iref) to clamp the maximum current when I want to limit it.







    --
    Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
    Davide Fabri, Feb 5, 2004
    #3
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