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LM74502-Q1: how to improve cutoff operating mode

Part Number: LM74502-Q1
Other Parts Discussed in Thread: LM74502EVM, LM74502H

Dear all, 

This topic is following this one: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1083210/lm74502-clamping-the-voltage-for-long-durations-1h---48vin-to-38vout/4010152#4010152 

I did test the LM74502Q1 cutoff operating mode thanks to the evm LM74502EVM, with the back-to-back mosfet design.

When going higher than Vin = 38 V,  ripple appears on the output and Vout max = 37 V. 

When increasing Vin (to approx. 42 V), the power is dissipated by switching losses from the first Mosfet (Q3). (and when increasing it too much, Mos temperature goes higher than recommended operating range, and the Mos is damaged)

Is there any way to improve this operating mode? Would using the LM74502H  version help ? if yes, how much would this help? (if possible quantify what maximum value could Vin be using the LM74502H version vs using the LM74502Q1 version)

Best Regards, 

P-A Burdet, AFAE