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TPS61021A: Comparison between EVM and WEBENCH

Kaji@PAN
Mastermind 7795 points
Part Number: TPS61021A

Hi,

I purchased an EVM and I'm evaluating the TPS61021A device now.
I have some questions in the evaluation result.
I will attach the evaluation result of EVM and the result of WEBENCH.

(1) I measured efficiency with EVM.
As a result, the efficiency is getting worse from 700mA.
In WEBENCH results the efficiency changes relatively slowly.
Is there any factor that degrades efficiency with EVM measurement?

(2) I confirmed the efficiency by changing the ambient temperature with WEBENCH.
As a result, efficiency gets worse at higher temperatures.
What is the factor that the efficiency changes with ambient temperature?

Best regards,

  • 0
    TI__Mastermind 40080 points

    Dear Sir,

    Did you check the voltage drop on the input wire with EVM. During the EVM testing, the voltage drop on the input wire should be take into account. You need to make sure the on board Vin=1.5V.

  • 0 in reply to Helen chen
    Mastermind 7795 points

    Thank you for your reply.

    The measurement point of the voltage of VIN was measured by J1 (pin of VIN) of the EVM.
    Therefore, I do not think that the voltage drop of the wiring is affected.
    Is there anything else you can think of?

    I have additional questions.
    (1) I measured the input current at startup. The measured waveform of the EVM is shown below.
    Current is gradually rising, but is this behavior normal?


    (2) I measured the behavior of input current after startup.
    The measured waveform of the EVM is shown below.
    The measurement waveforms of EVM are Vin 1.8 V, V out 3.0 V, I out 183 mA. At this time, input current fluctuation occurs.
    When I measure it, the input current is fluctuating in the following two states.
    · Pass-through (Vin / Vout without input / output difference) behavior
    Switching operation between burst mode and PWM mode
    Is it correct as behavior?
    Where is this cause?

    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 40080 points

    Dear Sir,

    The startup input current is right. when the soft startup finished, but still Vo<Vin, then will be a inrush current because of the maximum duty cycle.

    The ringing in picture 2 is abnormal. What is the length of the input wire? And did you make some change on the EVM board?

  • 0 in reply to Helen chen
    Mastermind 7795 points

    Thank you for your reply.

    Regarding the measurement environment, I will confirm a little more.

    As for the contents you asked before, how about the efficiency change when changing the environmental temperature with WEBENCH?

    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 40080 points

    Dear sir,

    Thanks for the update, when temperature rise, the efficiency will drop, generally 1-3% based on the change range. So their result is reasonable.