We are developing a new motor design with the DRV8850. Its a great chip, but we've had some unexplained failures. For no apparent reason, the driver will stop functioning. It then goes into a high current draw at idle. From 0.3 - 1.0Amp.
Its a very basic circuit:
driver VCC is a lithium polymer battery.
microprocessor VCC is 3.3V derived from the battery.
Some ideas we had that could be causing the problem:
1. In theory, the inputs voltage to the drv8850 could be higher than VCC.
2. We are using a very small SR resistor, 1k. Perhaps the ramp up is faster than the overcurrent protection.
3. We have a 10uF capacitor on the motor output for noise suppression. Perhaps this combined with the high slew rate is a problem.
4. Motor wires are extremely short. Only 8mm total from motor driver to motor terminals.