Hello,
I have been working on a design based on the DRV8302 chip. The input voltage is 12V, but I have tried different voltages as well. The problem that I have is that the fault pin always goes low and starts toggling when I enable the outputs and start to send PWM. The pulses at the output are very short, so I guess that some protection feature kicks in after a few microseconds on each pulse. The switching frequency is 50KHz, but I have tried 20KHz and 100KHz as well.
You can see the schematic here:
http://vedder.se/Temp/BLDC_3.pdf
I have double checked all component values and voltage tolerances and exchanged the DRV8302 chip to a new one three times with the same results. I have also tried to connect the OC_ADJ-pin directly to DVDD with the same result. The MOSFETs are definitely working and there is no short on any gate.
There are a few things that I suspect could be the problem:
* The OCTW pin is unconnected, so maybe I have to connect a pull-up to it to not trigger faults internally in the chip. (the FAULT pin is pulled up by the programmable pull-up in the microcontroller)
* The IRFS3006 MOSFETs are a too heavy load for the DRV8302. I have to use weaker MOSFETs.
* I have to toggle EN_GATE after the fault. I thought the DRV8302 did reset the fault by itself since the fault pin goes high again all the time and does not stay constantly low.
Do you have any idea what I should try next? I have already spent a lot of time on this.
Thanks in advance.
/Benjamin