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LM5122: quick start calculator with dual phase Interleaved configuration

Sam Ting
Expert 3600 points
Part Number: LM5122

Tool/software:

Hi team,

My customer wants to use the calculator to get the MOSFET power losses for thermal evaluation.
The design is a dual phase interleaved configuration with one high side MOSFET and "two" low side MOSFETs in parallel per phase.

Could you please guide me on how to fill in the MOSFET parameters correctly to get the power loss per MOSFET? (assuming the calculator is for one phase and one HS & one LS MOSFET). Thanks!

Filled phase number= 2.  

Need to fill MOSFET parameters: consider double or half for the configurations of dual phase and parallel MOSFETs? 

Regards,
Sam Ting

  • +1
    TI__Mastermind 30260 points

    Hi Sam,

    Thanks for using the e2e forum.

    Unfortunately, the efficiency table of the quickstart calculator does not have a feature for parallel FETs used.
    Like you already assumed, the calculator accounts for 1 HS and LS MOSFET per phase.

    If two MOSFETs are used in parallel on the low side, the overall Rds_on would be halfed, but the gate charge and gate-drain/gate-source charges would be doubled.
    The other parameters should not be affected.

    I would work with this method to fill in the calculator.

    Please let me know if there additional questions on the calculator.
    Best regards,
    Niklas