The low side drive does not look healthy.
Justas wrote: ↑
Oct 08, 2018 1:34 pm
Can somebody explain how this 9 fet configuration works? Seems like low side switch have 2 fets in parallel.
Yes, two in parallel on the low side but only one on the high side. In designs that are not using synchronous rectification, the low side FETs have to throw off more heat when they are acting like freewheel diodes.
The BBSHD controller apparently uses synchronous rectification. I have never tested the BBS02, but your waveform indicates synchronous rectification. Otherwise, the low side would only be switching for commutation and not at the PWM frequency.
So go figure why they used 9. Better than 6 but didn't have room for 12?