Hi,
We are a group of students trying to make a servo-lab for our university. We needed a motor-driver capable of driving both brushed DC-motors and stepper motors in chopper mode, and chose the DRV8814 for the Job.
Both the stepper and DC-motor are working fine while in fast decay mode(decay pin pulled high). However in slow decay, the stepper driver goes into fault-mode almost instant, and the DC-motor driver goes into fault sometimes, typically when the motor changes direction.
The setup for the motor driver is:
12 V supply(VCP pin measured to 23V), 0.15 Ohm sense resistors, the current chopping treshold is set to 2A(1A for the stepper motor). we are controling the chip with a digital signal on the phase-pin and PWM(32kHz) on the enable-pin.
motor resistanse is 2.37Ohm and motor inductance = 1,8 mH.
As far as I understand the datasheet the chip will only go into fault mode during overtemperature or overcurrent. As the chip barely gets warm, the problem must be some sort of current spike, right? Why wount this happend in fast decay? I tried putting a 10 Ohm, 1000pF snubber across the motor terminals, but it didn't seem to help much.
For the stepper-motor there is no problem driving it with fast decay, but for the dc-motor we would like to use slow decay.
Is there some way to fix this problem, or do we need a bigger driver?