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TPS92641: Questions about TPS92641 error amp behavior.

Kazuya Nakai59
Guru 21595 points
Part Number: TPS92641

Tool/software:

Hello guys,

One of my customers is evaluating TPS92641 for their next products.

At this moment, they have the following questions.
Could you give me your reply for them?

Q1.
Is TPS92641 error amp (EA) output switch behavior same between UDIM H/L control case and SDIM H/L control?
I think it is different and a switch which connected to EA output would be close/open depend on UDIM H/L level (SDIM=H).
Also I think the switch would be always close regardless of SDIM H/L level (UDIM=H). And the switching on time becomes the minimum when SDIM=H. 

Is my understanding correct?

Q2.
COMP pin is always charged to a voltage when SDIM=H (LED off). 
Could you please explain about internal circuit behavior?

Q3.
We confirmed rising speed of LED current is changed depend on comp charged voltage at just before SDIM turning L.
Is there any countermeasure to reduce this LED current rising speed variance 

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Mastermind 23190 points

    Hi Kazuya,

    I am currently out of office for Chinese New Year Holiday. I will reply to you on Feb.8 when I am back to office. Thanks for your understanding.

    Best Regards,

    Steven

  • 0
    TI__Mastermind 23190 points

    Hi Kazuya,

    I am back to office earlier than expected :)

    Please refer to my comments below - 

    Kazuya Nakai59 said:

    Q1.
    Is TPS92641 error amp (EA) output switch behavior same between UDIM H/L control case and SDIM H/L control?
    I think it is different and a switch which connected to EA output would be close/open depend on UDIM H/L level (SDIM=H).
    Also I think the switch would be always close regardless of SDIM H/L level (UDIM=H). And the switching on time becomes the minimum when SDIM=H. 

    Is my understanding correct?

    A1.  You understanding is almost correct. Only the last sentence has some errors. The correct one should be: The switching-on time becomes the minimum when SDIM = L.

    Kazuya Nakai59 said:
    Q2.
    COMP pin is always charged to a voltage when SDIM=H (LED off). 
    Could you please explain about internal circuit behavior?

    A2. LED is on when SDIM = H. I do not clearly understand what you want to ask. Please kindly clarify. Thanks.

    Kazuya Nakai59 said:
    Q3.
    We confirmed rising speed of LED current is changed depend on comp charged voltage at just before SDIM turning L.
    Is there any countermeasure to reduce this LED current rising speed variance 

    A3. I think you are referring to the LED current rising time when SDIM turns H. Am I correct? What is the variance you mention? Do you have any test results to illustrate this? Please kindly clarify. Thanks.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Guru 21595 points

    Hi Steven,

    Thank you vey much for your supports.
    And I'm sorry my question is not enough for understanding. 

    Could I discuss you this offline?

    May I sent you a waveform by e-mail?

    Thank you again and best regards,
    Kazuya. 

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 23190 points

    Hi Kazuya,

    Sure. We can talk through e-mail.

    I will close this thread. Please feel free to contact me again if you have any further question.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Guru 21595 points

    Hi Steven,

    Thank you very much for your reply.

    I will send you the waveforms.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 23190 points

    Hi Kazuya,

    You are welcome. Let's continue the talk through e-mail. Thanks.

    Best Regards,

    Steven