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TPS63901EVM: Regarding efficiency of TPS63901EVM at low currents.

Jagdish Karamchandani
Expert 1420 points
Part Number: TPS63901EVM
Other Parts Discussed in Thread: TPS63901

Hello support,

We are working on the IoT design where in we are trying to measure 1.25uA, 5uA & 10uA efficiency in TPS63901 eval board. Output is set to 2.5V & we load resistors corresponding to said currents. We keep varying input voltage & record the readings. The current is passed through 1E shunt & drop is measured with IA LTC2053 with gain of 1000. We adjust the offset of measuring circuit at each input but even though we are unable to get efficiency as shown in figure 8.3. Please see attached readings. 1.25uA readings are quite low & non-linear while 5uA & 10uA readings are better but still lesser than what claimed in datasheet. I am not sure if input bulk capacitance is causing some leakage. Will appreciate below queries from TI,

  • Do efficiency curves in datasheet include input leakage currents of capacitors?
  • Would you please advise setup & method used for deriving Fig 8.3 results?
  • Any known efficiency data of TPS63901 eval board because it contains tantalum & ceramic input capacitors which shall be having leakages.

Regards,

jagdish


TPS63901_Efficiency.xlsx

  • 0
    TI__Mastermind 27660 points

    Hi  Jagdish,

    • Do efficiency curves in datasheet include input leakage currents of capacitors?

             A from TI: Yes, the efficiency curves are based on EVM, not device only.

    • Would you please advise setup & method used for deriving Fig 8.3 results?

             A from TI: it is still bench test results, Just inrease the output current and recording the switching frequency. 

    • Any known efficiency data of TPS63901 eval board because it contains tantalum & ceramic input capacitors which shall be having leakages

             A from TI: correct, also some power loss of inductor, but i think it is no way to avoid in efficiency tests. just based on typical application is resonable.

     

    Regards

    Tao

  • 0
    Expert 1420 points

    Hello Tao,

    So do you think efficiencies that we obtain in attached sheet are OK as that don't match to datasheet curves particularly for 1.25uA there is large difference.

    Regards,

    jagdish

  • 0 in reply to Jagdish Karamchandani
    TI__Mastermind 27660 points

    Hi  jagdish,

    No, i think it does not make sense, but i am afraid it is hard to find out what happened. below is efficiency curve got in our lab. Yes, there is large difference.

    Regards

    Tao