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Original question:

LM74720-Q1: Ideal diode IC that can be put in the return side (negative side)

LM5051: Use one LM5051 + two FETs in parallel, or one LM5051 + one FET in two parallel circuits?

Conor
Guru 12000 points
Part Number: LM5051

Hi,

This is a continuation of "Related Questions".

I'm considering using the LM5051 that was previously introduced to me. It is expected that the Vds of External-FET will be regulated to 45mV(Typ). In that case, the external-FET loss is expected to be 17W since it will handle a load current of about 19A. So is it okay to use one LM5051 + two FETs in parallel, or one LM5051 + one FET in two parallel circuits? Points to note in this case, which method is appropriate? Also if you have any other recommended configurations, please let me know.

Thanks,

Conor

  • 0
    TI__Mastermind 45720 points

    Hi Conor

    The external-FET loss can be calculated by (I^2)(Rdson) since at 19A the FET should be fully enhanced ideally. But to estimate considering 45mV drop, power dissipation can be I*V = 19A*45mV = 855mW.

    Also,

    The two configurations you mentioned have different applications. 1*(One controller + 2 FETs) will have higher current capability whereas 2*(One controller + one FET) will act as an ORing. Load will not be shared in the second configuration.

    I hope this answers your question.

    Regards

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Guru 12000 points

    Hi Shiven,

    2*(One controller + one FET) OR-ing circuit does not share current. Therefore, if you are concerned about heat generation due to FET loss, we recommend a 1*(One controller + 2 FETs) configuration.
    Is the above understanding correct?

    Also, if the FET heats up due to large currents, are there any other recommended configurations?

    Thanks,

    Conor

  • 0 in reply to Conor
    TI__Mastermind 45720 points

    Hi Conor,

    FET should not heat ideally since the power dissipation is around 900mW only. But if heat generation is a concern, MOSFETs can be paralleled. So yes, the understanding is correct. 

    If FET heats up due to large current, you can parallel more FETs. 2 is just a starting point.

    Regards,

    Shiven Dhir