---------------------------------------- > Date: Mon, 10 Mar 2014 12:00:00 +0000 > Subject: Re: [EE]: pulse/rate limiter > From: cpmcsweeny@gmail.com > To: piclist@mit.edu > > On Mon, Mar 10, 2014 at 1:54 AM, Jesse Lackey = wrote: > > I'm not sure if I'm missing something here, but it seems what you're tryi= ng > to produce is a constant current, yet you're trying to do this using > digital rather than analogue control. The constant current controllers I'= ve > done (including those with uC control of current for dimming, using a PWM > output and RC filter to provide a control voltage) Exactly. He needs to cut out the middleman (comparator) and use the feedbac= k pin on the buck chip directly. =A0There is already a comparator inside. = =A0Another one will only add to the latency of the system. =A0The exact imp= lementation depends on the chip you're using. =A0I would say to look up the= datasheet. =A0There should be formulas for the proper component selection = and maybe even example circuits. =A0It all depends on the operation frequen= cy and the inductance value used in the output. The other important thing to remember when building a constant current sour= ce using a switching regulator is to use a non-inductive resistor or curren= t sense shunt. =A0For really high currents (say above 10A) a shunt should b= e used instead of a resistor. =A0A shunt is just a very low value resistanc= e. =A0I guess they call it a shunt instead of a resistor because it just lo= oks like a piece of metal or wire instead of a black thing with writing or = colored bands on it. Good luck, Robert =20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .