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LM5169:regulator problem

Jarim Kim
Prodigy 10 points
Part Number: LM5169

Tool/software:

hi.

It's a circuit using 48V to 12V using LM5169, but I keep getting the problem of dying.

The 48V is buried with the motor power end and has 5 10uF bypass caps.

The 12V output terminal is in use for internal power supply of the STEP DOWN board.

I'd like to get some help regarding the above.

  • 0
    TI__Mastermind 40040 points

    Hello Jarim,

    Is the motor at the output?    Are you sure you don't have excessive voltage back feeding to input - when motor stalls are breaks?  Thanks.

    If so, please a blocking diode between VOUT and Load.

    If this is not the case, please provide me with your specification and fill out calculator spreadsheet so I can review specification and check design against it.  Thanks.

    David.

  • 0 in reply to David Baba
    Prodigy 10 points

    Hello, David
    The 48V input terminal is buried in the battery and has a maximum of 70V specification, so it won't be a problem because the regulator input spec (120V) is.

    Then, are you saying to add a diode to the VOUT stage 12V output stage?

    If that's right, we'll add it and test it.

    Thank you.

  • 0 in reply to Jarim Kim
    TI__Mastermind 40040 points

    Hello Jarin,

    I am asking about your load.  Is it a motor, i.e. high inductance, if current is abruptly stopped, you will experience a voltage across the load that cause current to conduct in the reverse direction from NOUT to VIN.  If this is the case a diode will help.

    David.

  • 0 in reply to David Baba
    Prodigy 10 points

    Thank you for your answer.

    The load is the motor.
    If you apply a 48V input terminal diode, do you mean that it's serial?

    For diodes, do you use it with a 0.7V voltage drop in mind?

    Or do you connect it in a pull-down manner so that only the peak current is consumed in parallel?

    The big goal of the product is miniaturization, so it may be difficult to apply diodes that consume a lot of current due to their large product size.

    Thank you.

  • 0 in reply to Jarim Kim
    TI__Mastermind 40040 points

    Hello Jarim,

    please use a low forward voltage drop diode - Schottky.  let's check that we can prevent failure first, then decide how we are going to fit it in.  thanks.

    David.