piclist 2002\08\04\025139a >
Thread: LM3485 Hysteretic PFET Buck Controller.
picon face BY : Mike Singer email (remove spam text)

Thanks Roman and Matt,

I'll experiment with the chip when it'll be available to me. It seems I could reach 80-90% efficiency at 10khz (1:100). For a start I'll put open drains with resistors in place of a digital potentiometer.


> Mike Singer wrote:
> >  Has anybody any suggestions of max regulated frequency?
> > If I replace bottom resistor of feedback chain by digital
> > potentiometer and reduce output capacitor, what "max
> > frequency" very aprox could I send to digital potentiometer,
> > aiming at microstepping motor applications?
> > LM3485 can work at >1mhz.

Roman Black wrote:
> A good rule for PWM is 10:1. So if your PWM freq is
> 1MHz, (as above) you should not try to accurately
> simulate changing waveforms over 100kHz. Even 10 PWM
> cycles will cause significant ripple as you can't use
> large filter caps. 50:1 is better.
> -Roman

Matt Pobursky wrote:
{Quote hidden}

http://www.piclist.com hint: To leave the PICList

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