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LM5069: lm5069-1 start in resistive load

Davorin Kotnik
Prodigy 245 points
Part Number: LM5069

I made a circuit with LM5069-1, the same as LM5069EVM-627. The input voltage is 24V (22V-28V), the maximum current is 22A.

When I want to test the circuit (UVLO, OVLO, OC) on a resistive load (2 to 20 ohm), the circuit does not start.

With a capacitive load of 220uF to 1500uF, it works as expected.

I did a similar test on the evaluation module LM5069EVM-627 and everything works OK except that the current limit is 2.5A.

A circuit is attached. How to test the circuit?

Best regards,

DavorHotSwapLM5069-1-SurgeReverseProt-24V-22A.pdf

  • 0
    TI__Guru** 103806 points

    Hi Davor,

    Thanks for reaching out!

    Can you please fill the design calculator and send me for review.   The design calculator is available under LM5069 product folder on ti.com

    What is your actual load in your system ?

    Best regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 245 points

    Hi,
    to all four MOSFET,8400.LM5069_Design_Calculator_24V-22A.xlsx I added 10 ohms in series with the gates and the circuit is working with an ohmic load. I'm not quite sure why. But I will do all the required tests this week.

    The load for the circuit is two drivers for laser diodes, stepper motor drivers, oven heaters, control circuits, tec drivers.

    The calculation is attached.

  • 0 in reply to Davorin Kotnik
    TI__Guru** 103806 points

    Hi Davor,

    Thanks for sharing the details. 

    I suggest to test with your actual load. Do you have any control signal (ENable pin) for the loads ?. We recommend to enable the load using PGOOD output of LM5069 so that the stress on the hot-swap FETs will be reduced during startup.

    Estimate your load during startup and use those in the design sheet to arrive at the optimum parameters.

    Best Regards, Rakesh