LTC4367 for 40A Load

Hi, 

I am evaluating the over-voltage protection circuit and came across LTC4367. I wanted to know if I can use the same for a 40A motor load. I am trying to use it in between my buck and motor controller. My system is running on a battery? 

Thanks a lot for your help. 

  • +1
    •  Analog Employees 
    on Jan 18, 2021 7:05 PM 1 month ago

    It sounds like the LTC4367 could work for your application.
    Choose FETs with a low RDS(ON) so that temperature of the FETs stay below 175C at 40A.
    This can be checked with some simple calcs:

    PDS=RDS(ON)*40A
    TempRise=PDS*RϴJA
    TempAmbient+TempRise < 175C?

     Consult the datasheet for more detail about FET selection, as well as adding inrush control, and choosing a TVS.

    -Aaron

  • Thanks a lot for the information this really helps. Also wanted to know should I give the IC a separate power because I am concerned of the motor initial spikes can result in the IC shutting down sending the MOSFET into the linear region and leading to a blowup. Or if there is a much better method like bulk capacitance on the input etc. 

  • 0
    •  Analog Employees 
    on Feb 22, 2021 8:53 PM 8 days ago in reply to naman25

    If VIN goes negative from an inductive spike (> -40V), the GATE pin will connect to VIN to keep the FETs off. See page 7 of datasheet: the GATE pin description. Below is the relevant part of the block diagram on page 8.

    When the part is off, the GATE is connected to VIN or VOUT, whichever is lower, to keep FETs off.

    TVS or zener diodes should be used on the input to prevent the inductive spikes from swinging past the ABS max of VIN or the BVDSS of the FET. The amount of inductance at the input will determine how many TVS and zener diodes you need to absorb the energy stored in the inductance.

    When VIN is at its most negative value (-40V), check that the ABS max of the UV, OV, and SHDN pins are not exceeded, and that the current through the resistive divider is under 1mA.

    Some capacitance at the input would help stiffen the input rail should the supply momentarily drop out.

    Hope this helps,
    -Aaron