Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 64 subscribers
  • Views 147 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS92391: Some question of tps92391

Alan Xia
Expert 6555 points
Part Number: TPS92391

Hi team,

1. Is it set based on the lowest voltage of the LED light string?
2. The FB resistor has two modes: 2-resistor voltage division and 3-resistance voltage division. Based on previous experience, it is recommended to use 3-resistance voltage division when R1 (FB upper side resistor) is less than 200k.
Want to know the reason for this suggestion?
3. When using three resistors to divide the voltage, are there any requirements for the resistance range of the three resistors?

  • 0
    TI__Mastermind 28170 points

    Hi Alan,

    I am on a biz trip, will give you feedback tomorrow, thanks for your patience.

    BR

    Patrick

  • 0 in reply to Patrick Yao
    TI__Expert 6555 points

    Hi Patrick，

    Any updates?

  • 0 in reply to Alan Xia
    TI__Mastermind 28170 points

    Hi Alan,

    1. VBOOST_MIN is the minimum Boost adaptive voltage. If this value is set higher than the LED string voltage, the extra voltage will drop on OUTx pins.

    2. If two resistor-divider and less than 200kohm R1 used at the same time, the adaptive voltage range will be limited. If customer doesn't need a wide adaptive range, it is also ok to use two resistor-divider and below 200kohm resistance.

    3. There is no additional requirements except for those that are already listed in datasheet.

    BR

    Patrick

  • 0 in reply to Patrick Yao
    TI__Expert 6555 points

    Hi Patrick，

    Thanks for your help.

    The customer have further question：

    Patrick Yao said:
    1. VBOOST_MIN is the minimum Boost adaptive voltage. If this value is set higher than the LED string voltage, the extra voltage will drop on OUTx pins.

    The customer didn't understand here. During adaptation, the OUTx pin voltage is between 0.7~0.8V. What does it have to do with VBOOST_MIN?

    The specification book recommends R1/R2 to be between 7 and 15, which converted into VBOOST_MIN voltage is between 9.68V and 19.36V.
    The minimum voltage of our LED light string is 27V. In this case, what is the recommended VBOOST_MIN voltage setting?

    2. The specification sheet mentions that the initial boost voltage is approximately 88% of the minimum to maximum boost voltage.
    If the LED has been turned on before, will it start adaptive adjustment when it is turned on? Or will the voltage continue to rise to 88% before starting to adjust?

  • 0 in reply to Alan Xia
    TI__Mastermind 28170 points

    Hi Alan,

    1. VBOOST_MIN is the minimum output voltage TPS92391 could support. For example, the VBOOST_MIN is 18V, but the LED strings only need 15V, as a result, the Vout will finally be adjusted to ~18V. But if the LED strings need 20V, then the Vout could output 20V.

    2. I don't fully understand this situation, do you mean the IC off and wait for a long time, and then re-start the IC?

    BR

    Patrick