Strange behavior ST1S40

[MKhyz.1]

I use ST1S40 to power the microcontroller and SIM800C modem. Microcontroller uses 3.3V after LDO. The modem is powered on by the PWR_MODEM_ON signal and VT3-> VT2. Yellow line - power supply voltage + SIM_VBAT. Blue line + 3V8 after ST1S40.

Sometimes ST1S40 fails. I could see the moment when ST1S40 fails.

Often, after resoldering ic , this situation disappears.

Is it possible a situation in which ST1S40 loses FB voltage and opens the upper key to 100%?

What I have to redesign to fix this?

[Ivan FILYAEV]

Dear Maksym!

Have your layout re-design according our eval-board example been successful?

[MKhyz.1]

Hi. Yes. I have one example with re-design layout. It works well.