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TPS54361: Fail safe operation under Open Catch Diode

Koshi Ninomiya
Expert 5445 points
Part Number: TPS54361

Hi Team,

My customer is considering fail safe operation of TPS54361 under Open Catch Diode case.

Q1: If a catch diode becomes open, how does the TPS54361 operation become?

Q2: Does the TPS54361 have any features to detect open catch diode and stop operation?

 

Q3: What is an application solution to handle the open catch diode situation?

       Place two catch diodes in parallel?

Thank you.

Best Regards,

Koshi Ninomiya

  • 0
    TI__Mastermind 25590 points
    Koshi-san,

    Q1: The IC will still try to regulate if the catch diode is open. The high-side FET will ramp up the inductor current as usual, then when it turns off as usual. The current would usually go through the catch diode but in this case the current has to come from somewhere else. This current will pull the switch node low. The high-side gate is still low but the negative SW node will turn the high-side on in the linear region which will pass that current (and dissipate heat in the process). The low SW voltage and the poorly turned-on FET may damage the IC. These conditions are out of spec and we cannot guarantee any operation in this mode.

    Q2: No, there is no built-in feature to check this condition.

    Q3: You can definitely place two diodes in parallel. You may also add additional circuitry to detect this condition and shut off the IC (though it would still have to operate out of spec for at least one switch cycle and this may damage the IC).

    -Sam