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LM5122-Q1: About diode in schematic

Part Number: LM5122-Q1

Dear support team

I have question about TIDA01520.

(1)For what purpose is D1 attached?
(I think the purpose is to prevent the load current from destroying the high side FET.)

(2)My customer have issue that LS FET is destroyed.
it is said that it will not be destroyed if D1 is removed.
Have you ever experienced such a issue?


Tomohiro Nagasawa

  • Hi Tomohiro,

    D1 is placed there to lower the dead-time power dissipation of the MOSFET. During the dead time the body diode of the high-side switch conducts but it has a very high voltage drop. When the external diode is place there the voltage drop is decreased and the power dissipation is decreased. The external diode also has a faster reverse recovery time which will help to reduce the ringing of the switch node.

    I have never seen this before. My suggestion is to reduce R11 or add a diode in parallel to R11. Adding the diode will allow for slow turn on and fast turn off.


  • Hello Garrett-san

    Thank you for detailed explanation.

    I ask the customer to get the waveform. 


    Tomohiro Nagasawa