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LTC4357

Category: Hardware
Product Number: LTC4357

My name is Mati,

I am testing yours component LTC4357,

I have a question about its function.

I connect 2 components LTC4357 as below,

 

   

When I made short at 1 of the capacitors C9, or C10, the component act as expected and turn off the fet Q4 or Q6 correspondingly , so no

Current flow inside to the shorted power supply from the other power supply.

I had an un understood phenomenon wile I made short on the outside common load.

When I made that short, both gates of Q4  and Q6 were shut down to zero and the fets turned off so all the current from power supply 1 and 2

Flow to the load through the internal diodes of Q4  and Q6 and the fets got heated.

The reason I connect outside Aux Vcc to the VDD leg was to avoid such a phenomena.

Is this the expected function of this component LTC4357?

Is there a way to avoid internal shut down of the gate wile making a load short?

when i simulate the component at ltspice it worked o.k. 

Please advise

 

Best Regards

Mati

  

  • I had an un understood phenomenon wile I made short on the outside common load.

    When I made that short, both gates of Q4  and Q6 were shut down to zero and the fets turned off so all the current from power supply 1 and 2

    Flow to the load through the internal diodes of Q4  and Q6 and the fets got heated.

    I illustrated the situation you described and included the NFET body diodes.

    Pretend your circuit used silicon diodes instead of ideal diode controllers. What happens if you short the output?

    Is this the expected function of this component LTC4357?

    Yes.
    Ideal diodes handle input shorts, not output shorts.
    Ideal diodes regulate the forward voltage drop across the FET, not current.

  • hii Ashapiro,

    I just wonder why the gate of the ideal diode fet turn off while i made output short though i give independent auxiliary VDD,

    at that case that the fet (of the ideal diode) turn off at output short, i need to add a solution to protect the fet

    in case of output short, the stress at the fet can be up to 30-40 watt (depend of the my power supply ability at 

    current limit) in case of out short

    Mati.