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LMR43620MQ3EVM-2M: Efficiency gap between measurement and EVM document.

Shinji Tsuji
Genius 12898 points
Part Number: LMR43620MQ3EVM-2M
Other Parts Discussed in Thread: LMR43620-Q1

Tool/software:

Hi team,

I have a question about the variation of efficiency of LMR43620-Q1 at light load in PFM. 

I see below Figure6-3 shows efficiency at 200uA at VIN=12V is about 65%, while I measured using LMR43620EVM(2.2MHz 3.3Vout) and found the efficiency is about 85%.

Could you please advise possible reason why the efficiency is different between my measurement and EVM document?

Note : PFM frequency I measured at Iout=220uA is about 35Hz to 50Hz. 

regards,

  • 0
    TI__Genius 13825 points

    Hello,

    During light load operation the inductor will have a major impact on the efficiency. Are you using the exact same BOM and the same EVM part number as the User's Guide which that curve is found?

    Best regards,

    Ridge

  • 0 in reply to Ridge Lahti
    TI__Genius 12898 points

    Hi Larti-san,

    Yes, I am using exactly the same BOM and EVM.

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 13825 points

    Hello,

    The light load efficiency in PFM also depends on Ipkmin value specified in the datasheet. Variations in Ipkmin and the inductance will cause these kinds of variation in the light load operation. 

    Make sure to validate the end customer's efficiency in their specific application.

    Best regards,

    Ridge

  • 0 in reply to Ridge Lahti
    TI__Genius 12898 points

    Hi Ridge-san,

    I measured LM43620EVM-3.3V/2.2MHz for condition below and got 80% efficiency. 

    VIN=13.2V, Vout=3.3V, Iout=220uA

    As you mentioned above, this should be within part to part variation (inductance and other part also has variation) of this EVM. 

    I need a min/typ/max efficiency (or input current) at VIN=13.2V, Iout=230uA, Fsw=2MHz, Vout=3.3V for LM43610-Q1

    Could you please measure few LM43610-Q1 samples on EVM with EVM condition above to see min/typ/max efficiency?

    regards,

  • +1 in reply to Shinji Tsuji
    TI__Genius 13825 points

    Hi Tsuji-san,

    We specify the Ipeakmin value for min/typ/max in the device datasheet for PFM operation. PFM does not have as well defined of an efficiency as FPWM because PFM operation is dependent on both the Ipeakmin specification and variations in the chosen inductor. We don't have units with such variations to perform this test.

    Best regards,

    Ridge

  • 0 in reply to Ridge Lahti
    TI__Genius 13825 points

    Hello,

    Since we have not heard from you in a while I will be closing this thread. If you have more questions, you can re-open this thread by replying or create a new thread.

    Best regards,

    Ridge