Attached are waveforms of the Top FET drain-source voltage and Top FET gate-source in one phase of a 3-phase motor drive. I am trying to diagnose a 2V (or so) ring on the FET's gate signal. I'm currently running with a vbus across the bridge of 60V. The load is light - resistive, but with unknown amount of inductance since I'm using wire-wound resistors. The load R's are connected VBUS+ to OUT and VBUS- to OUT.
The ringing on the upper FET's gate occurs coincident with the turn-on of the lower FET. Conversely - I see similar ringing on the lower FET's gate when the upper FET turns on.
I do not know if this ringing should be of concern. Ultimately I'll be at VBUS = 300V and switching multiple Amps. Currently at 60V and sub-amps. I've tried slowing down the turn-on by increasing the gate R to 100 ohm. The gate rise time changes from about 700nS to about 5uS - FET turn-on time changes from about 120nS to over 1uS, but -the ringing is unchanged.
The FETs are N-channel STY80NM60 and the gate drivers are Avago ACPL333J.
Any ideas?
The ringing on the upper FET's gate occurs coincident with the turn-on of the lower FET. Conversely - I see similar ringing on the lower FET's gate when the upper FET turns on.
I do not know if this ringing should be of concern. Ultimately I'll be at VBUS = 300V and switching multiple Amps. Currently at 60V and sub-amps. I've tried slowing down the turn-on by increasing the gate R to 100 ohm. The gate rise time changes from about 700nS to about 5uS - FET turn-on time changes from about 120nS to over 1uS, but -the ringing is unchanged.
The FETs are N-channel STY80NM60 and the gate drivers are Avago ACPL333J.
Any ideas?
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