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TPS923655: Conditions for using TPS92355 as buck-boost

Oh SeHoon
Prodigy 10 points
Part Number: TPS923655
Other Parts Discussed in Thread: TPS922055, TPS922054

Hello, I have a question.

I'm currently trying to turn on a 12V LED using a Li-ion battery with 3 series.

Conditions to be used
1. Vin = 8V~12.6V
2. Vled = 12V
3. Iled = 2.5A
4. PWM dimming

  • The key question is whether the buck boost of the TPS923655 allows the LED to be controlled without any problems when changing the input voltage including the LED's Vf.
  • In addition, I would like to inquire whether there is a substitute available under the above conditions.

Thanks

  • +1
    TI__Mastermind 23180 points

    Hi Customer,

    TPS923655 cannot work with Vin = 8V, V_LED = 12V, I_LED = 2.5A in buck-boost connection due to the switching FET cycle-by-cycle current limit. (Please refer to Section 7.5 Electrical Characteristics from the datasheet.)

    We do not have any buck-boost LED driver that can fit all your working conditions. I would recommend you consider first use a constant-voltage boost regulator to boost your input voltage to an intermediate level, like 15V, and then use a Buck LED driver, like TPS922054 / TPS922055, to drive the 12V LED.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Prodigy 10 points

    Hello, Steven

    Thank you for your response.


    Additionally,

    I also use 12V, 2.5A LED as 6V, 5A.

    As far as I understand, there may be other reasons, but is it correct that TPS923655 cannot be used even when the LED is used at 6V, 5A because it is not within the switching FET Cycle-by-Cycle current limit? (TPS923655 → 5.8A to 7.6A)

    Thank you.

  • +1 in reply to Oh SeHoon
    TI__Mastermind 23180 points

    Hi Customer,

    Oh SeHoon said:
    As far as I understand, there may be other reasons, but is it correct that TPS923655 cannot be used even when the LED is used at 6V, 5A because it is not within the switching FET Cycle-by-Cycle current limit? (TPS923655 → 5.8A to 7.6A)

    Yes. You are correct. TPS923655 cannot work with Vin = 8V, V_LED = 6V, I_LED = 5A in buck-boost connection due to the switching FET cycle-by-cycle current limit.

    Best Regards,

    Steven