ltc3779, the BG pin shorted to GND when input voltage is greater than 50V, why it happen?

I am using ltc3779 to design a PS, the input voltage range is from 6V to 100V, the output is 31V. Now the PS can work when input voltage decrease to 6V. But unfortunately, the BG1 pin shorted to GND when input voltage is greater than 50V, it happened two times. 1k ohms is used between VIN pin and VINSNS pin, I think there is some wrong, but I don't know why? Could you help me?

Attached sch for your reference.PDF

  • Hi Alex.Sun

    We have seen similar failures of BG1 pin in two different designs with the LTC3779, one is a 9-51V to 12V/4A conversion, the other a 9-51V to 48V/1A conversion (nearly identical to the datasheet designs fig 17 and 18). The converter is correctly functioning but the BG1 pin suddenly failed on some boards (only about 2V drive instead of 10V, increased current consumption, internal 2 Ohm "short" from BG1 to PGND). Both designs have been operated at 24V only (switched off/on several times) before the failure.

    Have you been able to solve your issue with BG1? What was the root cause?