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Original question:

LM74900-Q1: LM5074900-Q1: Schematic Review

LM74900-Q1: Efficiency required

Balakrishnan kumar
Prodigy 50 points
Part Number: LM74900-Q1

Tool/software:

Hi Team,

I am working on calculating the input current for the LM74900-Q1. However, I noticed that the efficiency values are not provided in the datasheet. Could you please share the efficiency figures for the following parameters?

Load current: 5A
Input voltage: 12V


Additionally, could you confirm if the input current can be calculated using the formula (Iin = Iout/efficiency) for this ideal circuit breaker?

Thank you for your assistance.

Best regards,
Bala

  • 0
    TI__Mastermind 49085 points

    Hi Bala,

    LM74900-Q1 is a gate driver. It will drive the GATEs of the MOSFETs in the power path. Iin will have components I1 and I2, where I2 is basically IOUT and I1 is inrush of the Cin.

    In the power path only losses that will occur are conduction loss the FETs Q1 and Q2. Where Q1 will be regulated at VDS 10mV and Q2 will have a drop of Iout*RDS_ON.

    Hence VOUT = (VIN - 10mV -Iout*RDS_ON). Efficiency can be calculated as (VOUT*IOUT/VIN*IIN) whereas IIN is same as IOUT in steady state (no inrush current).

    Therefore, efficiency is VOUT/VIN, and it cannot be generalized because of change in RDS_ON of MOSFETs and load currents.

    Regards,

    Shiven Dhir