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LMR43620: IQVIN and efficiency with FPWM

Dice-K
Mastermind 6927 points
Part Number: LMR43620

Tool/software:

Hi support team,
I have questions about using LMR43620MB5RPER with FPWM.

Is the IQVIN below data for Auto PFM?

Is there an IQVIN for FPWM?

Also, I think the efficiency graph below is data for Auto PFM.

Is there an efficiency graph for FPWM?

Regards,
Dice-K

  • 0
    TI__Genius 12995 points

    Hi Dice-K, 

    The non-switching input current should not be affected by the mode (AUTO vs FPWM) and should therefore be valid for both.

    The supply input current is for AUTO. I took the supply input current for the device in FPWM at 2.2 MHz, 12 VIN and found it to be 8.26 mA. This data was taken on the auto version of the part, but this should be virtually identical to the industrial trim. 

    In terms of an efficiency graph, you can find an FPWM graph for the 1 A device in figure 8-6 of the LMR43620-Q1 datasheet. Two differences are of note:

    • The graph is taken of the device at 2.2 MHz. There should not be too large of a difference between the part's performance at 1 MHz than the part's performance at 2.2 MHz. You may need to utilize a different inductor to optimize your inductor current ripple to minimize your switching losses at a different switching frequency. Equation 7 of the datasheet outlines this in more detail.
    • The graph is taken with the 1 A version of this device. This should not affect the device's efficiency either too much. Due to the higher current limit, the 2 A device may perform marginally better than the 1 A version, but as an estimate this graph can be used to characterize the 2 A device's efficiency at lower loads in FPWM. Past ~ 300 mA, the device will behave identically between its FPWM and AUTO operation.

    Thank you,

    Joshua Austria