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TPS92641EVM: Design operations and clarifications

ArTzy
Genius 17415 points
Part Number: TPS92641EVM
Other Parts Discussed in Thread: TPS92641

Tool/software:

Hi Experts,

We have some questions about this EVM for experimental set-up: TPS92641EVM.

[1] The power supply we have is 48V. Can we use a lower supply voltage, such as 15V, since we only need to drive one LED?

[2] What is the operating frequency range for switching the LED on and off? Can it reach up to 2MHz? Is the frequency adjustable on the EVM board, as we need a varying frequency? Additionally, can we choose different types and numbers of LEDs with flexibility.

Thank you.

Regards,
Archie A.

  • 0
    TI__Mastermind 23150 points

    Hi Archie,

    Sorry. I am currently out of office. I will reply to you tomorrow when I am back to office. Thanks for your understanding.

    Best Regards,
    Steven

  • 0 in reply to Steven Li
    TI__Genius 17415 points

    Hello Steve,

    Noted on this. Thank you.

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Mastermind 23150 points

    Hi Archie,

    Sorry for the late response. Please refer to below answers to your questions.

    [1] Yes, you can use a lower supply voltage like 15V. (Please make sure than Vin is higher than 7V. You can refer to Section 6.3 Recommended Operating Conditions from the datasheet) You need to modify some components on the EVM so that it can work.

    [2] The operating frequency range for switching the LED on and off will mainly depend on your circuit design. You can reach 2-MHz LED switching on/off with shunt FET PWM dimming feature of TPS92641. The frequency can be adjusted on the EVM. You can choose different types and numbers of LEDs with flexibility but you may need to modify some components on the EVM so that it can work.

    Best Regards<
    Steven

  • 0 in reply to Steven Li
    TI__Genius 17415 points

    Hello Steven,

    Thank you. We have follow up:

    a)Ehat determines the magnitude of ripple LED current?, is there a way to reduce it?
    b)Can we implement something like this?
    example:
    when PWM signal High - 2.3 V , 400ma
    when PWM signal Low - 2v,20ma
    c)How much time does it take for the system to stabilize after powering on (refer to Figure 10)? Additionally, what are the rise time and fall time of the LED current when the PWM signal changes from high to low or from low to high?

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Mastermind 23150 points

    Hi Archie,

    Sorry. I am currently out of office. I will reply to you next Monday when I am back to office. Thanks for your understanding.

    Best Regards,
    Steven

  • 0 in reply to ArTzy
    TI__Mastermind 23150 points

    Hi Archie,

    Please refer to my comments below.

    a) Please refer to Section 8.2.1.2.4 Set Inductor Ripple Current and Section 8.2.1.2.5 Set LED Ripple Current and Determine Output Capacitance, COUT from the datasheet.

    b) May I understand what does the 2.3V / 2V refer to?

    c) The stabilization time will depend on a lot of factors like your system input / output conditions, component selection, etc. The rise time and fall time of the LED current mainly depends on your system input / output conditions and component selection.

    Best Regards,
    Steven

  • 0 in reply to Steven Li
    TI__Genius 17415 points

    Thank you, Steven.

    We have procured the TPS92641EVM we had some doubts enclosed in the attachment below:

    TPS92641_EVM.docx

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Mastermind 23150 points

    Hi Archie,

    Please let the customer first connect the LED load and then do the test.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    TI__Genius 17415 points

    Thank you, Steven.

    We connected the LED load and tested it. The output voltage was a constant DC voltage with no ripples. Additionally, the PWM signal at the UDIM pin did not seem to have any effect on the system, as the output remained constant with or without the signal, contrary to what is shown in the datasheet.

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Mastermind 23150 points

    Hi Archie,

    if you are using the default EVM setup with no components changed and power the board with Vin = 12V, then the device will never get out of UVLO. You should change the UDIM resistors. You can refer to Section 7.3.5 Undervoltage Lockout (UVLO) from the datasheet. Other components on the board may also need to be altered accordingly to make the board work at your working condition.

    Best Regards,

    Steven