We're having some trouble with a small inverter motor design (24V / 20A).
We're seeing quite a lot of ringing on the high-side mosfets, we scope it with the negative of the oscilloscope on the phase output and the positive at the +VDC and here's what we see :
We're seeing spikes of over 8V over the VDC_bus and 7V below.
We're using a DRV832x for gate-driving and this is with the standard settings (1A sourcing, 2A sinking or is it the other way around?). We tried to lower these gate current values all the way down to 20mA but it actually doesn't change much the ringing, only makes the switching slower and sometimes even drops some events, maybe an internal protection against switching too slow?
We don't see this behaviour on the low-side at all where all is fine and dandy.
The layout is done according to the rules with trace lengths being balanced (we're driving 2 MOSFET per switch) and the inductive loops / stray inductance minimized as much as possible so we're quite surprised to see this behaviour. The DC link is basically 220µF of MLCC which should give us some low ESR / ESL.
Any lead on how to minimize this? Could it be a measurement effect of us not scoping it correctly?