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LM5012-Q1: protection against output short circuit to the battery

Jafar Chegini
Prodigy 90 points
Part Number: LM5012-Q1
Other Parts Discussed in Thread: LM5012, LM74610-Q1, LM74700-Q1, LM5060

Hi,

I am using LM5012QDDARQ1 in my design. the output goes to a connector. lets say, the output shorted out to the battery positive +32V, what will happen to the converter? does it have protection against this? if not, how can I protect my converter?

Thanks

p.s. here is the complete design:

  • 0
    TI__Guru 73500 points

    Hi Jafar,

    Thank you for designing with the LM5012.  According to your schematic,  in such an event,  the IC will stop switching but the high side FET's body diode will conduct the back flow current from Vout to Vin, and it may damage the IC.  

    To protect against such issue, you may employ a smart diode like the LM74610 or the newer parts of similar functionality.

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 90 points

    Thanks for your support. do you think the following concept will work for my protection goal? any advice?

    Regards,

    Jafar

  • 0 in reply to Jafar Chegini
    TI__Guru 73500 points

    Hi Jafar,

    It would.  If you care about the output voltage regulation during normal operation, you may consider to move the feedback resistor divider to the output port.  In this way the series FET's voltage drop would be compensated by the loop.  

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Guru 73500 points

    Hi Jafar,

    I would suggest LM74700-Q1 over LM74610-Q1.  The later may cause to short interruption (small voltage drop) once awhile, while the LM74700-Q seems overcome that and operate continually. 

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 90 points

    Hello Youhao,

    Thanks for the info. here is my updated circuit, please have a look and let me know tour comments. I also have questions below:

    In scenario.1, the output shorts to +32, we already talked about it. but, what if the output is shorted out to GND (scenario.2)? what will happen in this case, are we safe? 

    in all scenarios, is the EN pin safe to be connected to Anode? could it make a problem?

    Many Thanks,

    Jafar

  • 0 in reply to Jafar Chegini
    TI__Guru 73500 points

    Hi Jafar, 

    If this is the case, you may consider to employ a circuit breaker type device like something below to replace the LM74700 circuit. 

    If you can do this, I will direct this to our experts of such devices for they may have something newer than the LM5060.  Please kindly advice.

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 90 points

    Hi Youhao,

    I already know LM5060, But I was hopeful for less complicated solutions. I will try to simulate the LM74700 solution, based on the results we will decide.

    Many Thanks,

    Jafar

  • 0 in reply to Jafar Chegini
    TI__Guru 73500 points

    Hi Jafar,

    Understood. Please let us know if we can be of further assistance. 

    Regards,

    Youhao