LT4356-1 failure during hot plug

Dear support,

      I have a power supply front end design using LT4356-1 as below.

     The IC failed after a few times' hot plug when I was doing the inrush current test. 

     The gate voltage never pulls up over VOUT when the failure. 

     Below is the transient voltage plot appeared on VCC (in yellow) and SNS (in green).

    I had a 10 ohm in series of VCC line. I am not sure whether it is the SNS maximum rating of VCC+0.3V that is causing the issue.

    Could anyone help on this?



  • Forget to mention, I do have a 40v TVS in front near the connector.

  • Good that you have the TVS (as suggested by the "Supply Transient Protection" section in the LT4356 datasheet which you should read through also) because that is usually the first suspect when IC is damaged. But it needs to be near the LT4356 VCC and GND pins. Therefore, check that the VCC pin voltage during transients is always below its 100V absolute maximum rating if the TVS is far away from the LT4356 VCC and GND pins. Look for other pins that may have exceeded their abs max. Try using a resistor in series with the 47nF gate capacitor to limit current flow into the pin. Note that Icc flowing through the 10 Ohms will raise the overcurrent fault threshold from the expected 50mV. Check if the MOSFET is also damaged. Do not rely on parallel switch MOSFETs to share the power dissipation stress that occurs during startup inrush or overvoltage/overcurrent regulation, i.e., each switch MOSFET's safe operating area (SOA) should be sufficient to handle these stressful conditions by itself.