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LM53625-Q1: Do's and Don't's

Koji Hayashi92
Mastermind 7030 points
Part Number: LM53625-Q1

Hi TI-team

My customer want to know about the following in the datasheet.

Don't: Allow the output voltage to exceed the input voltage, nor go below ground.

It's understandable because it's not working properly.

Why is it prohibited ?

Is it because the current flows through the diode of the MOSFET in Hiside and is broken ?

 

Best Regards,

Koji Hayashi

  • 0
    TI__Mastermind 22301 points

    Hi Koji,

    You are correct, there is a parasitic body diode across the high-side MOSFET that will conduct reverse current if VOUT > VIN.

    This can damage the device, you should be sure VOUT is not being supplied by something else in the circuit, otherwise you would need some kind of reverse current protection.

    Hope this helps,

    -Orlando 

  • 0 in reply to Orlando Murray
    Mastermind 7030 points

    Hi Orlando-san

    Thank you for response.

    If possible, could you tell me the drain reverse current (continuous) and drain reverse current (pulse) of the target FET ?

    In addition, my customer think there may be a momentary interruption of Vin (it is difficult to set it to 0 on in-vehicle products).

    With this specification, Vin voltage may be 6.8V for 1.5 seconds. (Normally Vin=11.5V Vout setting 7.5V)

    Will the IC be destroyed in this state ?

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    Mastermind 7030 points

    Hi Orlando-san

    How is the situation here ?

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    TI__Mastermind 22301 points

    Koji,

    We do not specify the reverse current as it is carried by the parasitics.

    Typically if VIN drops for a moment, the converter should be ok, the load will cause VOUT to drop with VIN and the converter would enter a dropout operation.

    Avoid having VOUT powered externally. Also avoid large capacitance on VOUT.

    Is your customer seeing issues? One fix is a low forward drop schottky diode on VIN to prevent reverse current.

    -Orlando