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Recommendation: 10-14Vin; digitally variable 6-15Vout @ 5A

Errol Kowald
Intellectual 540 points
Other Parts Discussed in Thread: TPS61170

I am struggling to find a controller or converter that can be digitally varied by means other than a digital potentiometer. I assume that this could be achieved by replacing the internal reference with an external one, provided by a microcontroller, but I can't find anything that provides this facility, as well as satisfying the specs - 10-14Vin 6-15Vout @ 5A

Can anyone suggest a way to do this?

  • 0
    TI__Guru 72695 points
    I would use webench to test different converters/controllers that would give one design to meet your requierments.
    Then use a resistor from the FB input to a DAC.
  • 0 in reply to Frank De Stasi
    Intellectual 540 points

    I don't see how connecting a DAC through a resistor to the FB input will achieve digital control. A digitally controlled potentiometer from FB to gnd would work, by altering the Vout divider ratio, but that's what I am trying to avoid. If it was possible to replace the Vref to the error amp we'd be getting somewhere.

    All is not lost though. I have just stumbled across an article "Designing DC/DC converters based on SEPIC topology" - SYLT309, which uses a TPS61170 as an example. Curiously, that controller has a 1-wire interface called Easyscale, which enables the user to select x/32 of Vref, where x = {0 - 31}, and hence Vout. It also has the ability to accept a pwm signal and divide the reference by the duty cycle. This might even give finer control.

    So the question of digital variation is largely solved.

    Now all I've got to do is work out how to coax 5A out of the TPS61170. Any ideas?

  • 0 in reply to Errol Kowald
    Intellectual 540 points

    Getting 5A out of a TPS61170 appears to be a lost cause.

    The only device I've found so far that provides digital control and 5A in a single package is MAX16992. It has an external Vref input, which can easily be provided by a filtered PWM port pin, and the ability to drive an external FET, thus allowing the 75W I am looking for.

    TI apparently has no similar device, or at least, none have been offered.