I want to build a PWM controller for a 48vdc fan. The Microchip TC646 temperature-regulated, PWM speed controller looks like a good chip to do this and a little more.
The recommended circuit in the datasheet has fixed upper and lower speed limits using fixed resistors (p. 16):
http://ww1.microchip.com/downloads/en/D … 21446D.pdf
If I want to change this circuit so that the limits can be adjusted via pots, which resistors should be replaced with pots? Is this as straightforward as using trimmers in place of R1 & R3?
Also, Microchip makes a plethora of other chips in this family, (the complete family is 642, 646, 647, 648, 649.) The datasheets read as duplicates except for the Behavioral Algorithm. Any idea what the differences are?
Thanks,
Dave