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LM5050-1-Q1: LM5050 Reverse Protection Configuration Diode Selection

Michael Raleigh
Expert 3245 points
Part Number: LM5050-1-Q1
Other Parts Discussed in Thread: TIDA-01167

Hello,

I need some clarification on the sizing of D1 and D3 (as referenced in section 8.2.6 of the ds), do they need to be rated for 60V at 1A schottkys? Don’t they just have to handle the quiescent current of Vs itself? 

Thanks,

  • 0
    TI__Expert 5615 points

    Short answer: It depends if they need to pass unsuppressed transients and if so, how much they can clamp to.

     

    Long Answer: I'm pretty confident 60V 1A schottkys were what was used when testing this design. You are right regarding the sizing, 1A is fine since the current through IC is minimal. The voltage may need to be higher if they need to pass "unsuppressed" automotive transients ( which are greater than 60V) and if they don't have TVS strong enough to clamp below 60V.

     

    The LM5050 has a 100V absmax rating so we have a lot of headroom.

     

    Basically if they can clamp VIN transients below 60V then you would use 60V schottky and 60V Vds rating for the external MOSFET(s).

     

    If they plan to design a smaller clamp circuitry and use 100V Vds MOSFETs then they should pick 100V or higher schottky.

     

    Check out TIDA-01167 which is not an ORing controller (does not detect reverse current) but it may be of interest for their application.