Re: DRV8825 vs TMC2100 vs THB6128

the internal guts of the control chip switches at a fixed internal rate that has nothing to do with
micro stepping freq - - - it acts like a switching regulator by varying the fet on times - - -
in the stepper control chips - - there is a current sense resistor that provides the current feedback

thus the amount that the caps are worked at - - depends upon the phase angle - - - the decay mode
fast decay or slow decay - - - fast means more current change during the internal on and off cycle of the fets
meaning more ripply currents are present - - -

nothing to do with micro stepping rates - - -

I am playing around with some control electronics and looking at all ceramic caps - - - no AL caps - - why?
much better esr - - - as in close to '0' most designs have a small 1 uf cap close the control chip with 100 uf a short distance away
22uF ceramic caps at 16 volts are cheap now days - - - and are small 0805 case size - - - and feel that 4 of these will be more than
enough - - -

note the fet on and off times are in the 40 nSec range - - AL caps poor at those freq's.