Hi,
We’re using DRV8332 drivers to drive several BLDC in our system. On one of the axes we experience strange driver behavior when trying to accelerate past a certain speed.
The first figure below shows the three phase current measurements along with the FAULTn signal (brown). The motor spins with 4900 rpm before the acceleration starts at around -0.3 s in the figure. As you can see the driver shuts the output down at 0 s, but without signaling any fault condition.
Since the motor continues to spin it will continue to commutate and seemingly resume drive. Because of high gain the controller will have increased the duty cycle so the driver soon shuts down again. But FAULTn is not asserted until around 0,25 s.
Another test run is seen in the figure below. It shows one phase current (red) zoomed in. It seems like the phase is shut down (at -20 ms) for 120 degrees during its Low Side ON state, still no fault condition (brown).
We use trapezoidal control according to the TI DRV8312EVM sensored example code (hard chop). The driver is set to Over Current Latching mode.
My question is, why does the driver shut down? And why doesn’t it signal any fault condition?
Best Regards,
Johan