I'm implementing a BLDC controller using the DRV8302 chip and IRFS7530 fets. I am debugging a problem where GVDD drops rapidly and causes a GVDD undervolt fault. So far, I have done some preliminary analysis. I have the system running at 12V and have a 1000uF capacitor near the FETs. From probing, I can see that PVDD, DVDD, and AVDD are all stable at the correct voltages. GVDD is stable at about 11V when there is no switching, but when it tries to switch the FETs, the voltage drops to 8V in a few uS (I will try to get a scope capture). Weirdly, this only happens when I have a motor connected and does not happen when there is no motor. Because I am using FETs with large gate charge (236nC), I have the switching frequency limited to max of 20kHz to stay under the 30mA gate driver current limit.
My question is what are some main causes for GVDD to drop so rapidly? Is it possible that the internal charge pump has failed?
I have attached my schematic for the DRV8302 and power fets for reference.