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DRV8305-Q1EVM: Protection the MCU from over-voltage

Part Number: DRV8305-Q1EVM
Other Parts Discussed in Thread: DRV8305-Q1,


I have a question in the MOTOR & BEMF Sense section in page 4 of the DRV8305-Q1EVM schematics. Three Schottky diodes, D11, D12, and D13 were used to protect the MCU from over-voltage (>3.3V). These Schottky diodes are connected between VSEN A/B/C and VREG/VREF (pin 48 of DRV8305-Q1). My concern is that VREG/VREF is connected to an internal LDO in DRV8305-Q1, which cannot sink current. If the BEMF voltage was over 45V, there would have a current flow through these Schottky diodes to VREG/VREF, which many damage the LDO. Could you please advise whether my understanding is correct?

My approach to fix the problem is to replace these Schottky diodes with three 3V3 Zener diodes and placed them between VSEN A/B/C and GND. Could you please comment on my approach?