I have a piece of test gear I am working on designing, in which there I need to drive a number of N channel mosfets, (3 high side, 2 low side)
I found there is a very large range of gate drivers intended for driving 3 phase motors, and thought this would be a good option as it would provide the drivers I need in a cheap, & space efficient package.
I am roughly aware of how the bootstraping circuit works, and the limitations it places on maximum on time. However I expected be able to generate longer than I am. I would like to be able to generate pulses at least 200ms long, but with the current setup only seem to be able to manage about 5ms before the Bootstrap voltage monitor kicks in.
I am running with a 15V supply, and my bootstrap capacitors are 0.1uF
Searching through the datasheet I did find "GHx Passive Pull-Down Resistance" specified at 400kΩ this seems pretty low to me but would potentially explain my problem.
I assume this property is intrinsic to the device and cant be changed, is there anything I can do to increase my maximum on time.
The only thing I can think of is increasing my bootstrap capacitor size(and correspondingly Vreg capacitor). However I don't know what controls the sizes I can use, can I just throw a 20uF capacitor in and call it a day or will this fry the bootstrap diode.
As a further down the road backup option (requiring a PCB redesign) what factors would need to be considered before switching to something like a TMC6200 with an integrated charge pump to allow 100% on time operation.