Hi team,
My customer reported an issue with DRV8818: the driving current cannot be reduced to target (VREF/(8*Risense) in step holding mode. In fact the current is basically fixed at arround 1A no matter what VREF is applied. Such as with VREF=0.3V and Risense = 0.1 ohm, the drving current should no more than 0.4A, while in fact it is measured arround 1A, no matter what kind of decay mode was used.
I think i have found out the root cause: it is due to long blanking time. Customer use 1nF on RCx pins, so tBLANK is about 1.4us, such long blanking time result the driving current is out of control. I have tried to reduce the capacitance down to 100pF, the problem fixed.
However, the question is, our datasheet recommends capacitance from 470pF to 1500pF, 100pF is out of this range. I do not understand why we place this limitation on Cx capacitance? How to solve this problem if 470pF is too large?
Thank you,
John
