Hello,
We are using the DRV8871 to drive a brushed DC motor using motor with the following settings:
* Load = Brushed DC motor
* VM = 40V
* Frequency = 5kHz
* In1 duty = varies between 10% and 100%
* In2 duty = 0%
* Imot = Between 1.3A and 2.8A
* ILIM = 20k
* Test Duration = ~10 minute intervals with fixed In1 duty cycles.
We were able to execute several tests where we ran the motor at a fixed In1 duty cycle for approximately 10 minutes.
After each 10 minute test we adjusted the duty and ran another test. This was performed for several hours over the course of several days.
During one test the DC motor was prematurely disconnected from DRV8871 prior to disabling the drive and turning off power (In1 was at logic high, In2 was at logic low, and 40V was supplied to the DRV8871).
Within 5 minutes, the DR8871 failed resulting in low resistances between the following pins: IN2, OUT2, VM, and GND.
We understand that this may be the result of user error by removing the DC motor prior to turning off the system, however, we do not want to dismiss other sources leading to the failure.
It is peculiar that the device would fail when operating with no load as there is no current path to cause heating in the high and low side transistors.
If it were due to back EMF when the motor was disconnected we would have expected immediate failure instead of the ~5 min it took for it to fail.
Is there something about driving this IC with no load that overstresses the part?
Any thoughts on how/why this failed in an unloaded operating state would be appreciated.
Thank you.