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LMG5200: Switch Node Ringing Undershoot Concern

Part Number: LMG5200


We are using the LMG5200 half-bridge modules in a multiphase GaN inverter for motor drive applications. When driving a simple three-phase inductive load (1mH load), we are observing undershoots on the switch node outputs exceeding the -5V rating reported in the datasheet. The peak undershoot is around 50% of the DC-Link Voltage (eg. -10V undershoot with 20Vdc). We understand that the main contributor to this ringing are the parasitics on the commutation loop and as such, we followed the same layout as the TIDA-00909 reference design. The probing was carried out using a passive 200MHz oscilloscope probe with a ground spring. We are now hoping to make some changes to the board to tackle this issue. So far we made two changes based on similar questions on the forum. We separated AGND and PGND and emptied out any copper underneath the switch node outputs to minimize parasitic capacitance seen by the switch node. I was wondering if you had any other advice regarding this issue 

Also, I was hoping you can address these questions that I had

- Where does the -5V absolute maximum rating in the datasheet come from 

- What are the consequences/failure mode of the device if we repeatedly exceed this threshold 

Thank you in advance