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Different inpult voltages lead to destruction???

Question asked by Nelson Scheja on Aug 14, 2019
Latest reply on Aug 21, 2019 by Nelson Scheja


In my current project I'm using the PF8100 as PMIC. Please see attached schematics. The internal logic, SW1-4 and LDO1-4 are supplied by 3V3, while SW5-7 are supplied by 5V.

When testing the first PCB prototypes, the PF8100 always gets destroyed somehow, drawing a lot of current from 5V. Seems like a shortcircuit. This even happens when all output voltages are inactive (no event on PWRON pin).

Further testing showed that no shortcircuit occurs when I reduce the 5V to about 4.5V. Somewhere around 4.7V, drawn current increases drastically, leading to some fault.

I have searched through the datasheet several times and could not find any single mention that forbids using different voltages for the DC-DCs. 3.3V and 5V are both well within the specified limits, and the block diagram suggests that each DC-DC is an independent unit receiving its own independent supply via SWxIN.

Can you please explain why the IC burns with a 5V supply?