I have a simple DC-DC step-up circuit using a MAX1771 controller, but it doesn't actually do any stepping up. It's connected as shown in Fig. 2c of the datasheet, with different resistors to get the output voltage I want. (R1=34.2k, R2=330k to get 16v.) Input is 12.85v on my test bench; will be 12-14.5v or so when connected to a car battery.
I've got a 1.1k load resistor on the output, which is at 12.61v (essentially the diode drop down from the input). The FET control signal is putting out a 7v spike at about 130kHz, but the pulse width is only about 0.04uS.
I think the pulse should be wider to build up more current/field in the inductor, which would then charge up C4 on the output to the expected voltage. Anybody have a suggestion for what I should look at to see why it's not working better?
Thanks, dhm