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TPS92691: Separating the conversion input voltage and the device input voltage

Ryuji
Guru 20090 points
Part Number: TPS92691

Hello,

I'm looking forward to the LED driver for meet the following specifications.

<Requirement 1>
Vin: 3.6V~6.8V
Vf=3.2V
LED=2S2P
ILED=1A
Analog Dimming
Can be used for 10ms~30ms Flash Operation

<Requirement 2>
Vin: 3.6V~6.8V
Vf=3.2V
LED=1S4P
ILED=1A
Analog Dimming
Can be used for 10ms~30ms Flash Operation

Can I use TPS92691 for the above specification if I seprate the conversion input voltage and the device input voltage?
I found that the LED driver which can be used for 3.6V of VIn(min), I would like to separate these voltages. 
Please see the attached file.
TPS92691.pptx

Also, could you please let me know more suitable device for these requirement if there is?

Best Regards,
Ryuji Asaka

  • 0
    TI__Mastermind 25500 points

    Hello Ryuji,

    For those current levels the TPS92691 is a good choice. Yes, you can use separate voltages for the power input and VIN. Just make sure the voltage supplying VIN is capable of supplying the VCC current required for the gate driver and the quiescent current of the device. It will need to be able to supply Iq + Qg*Fsw where Qg is the gate charge of the chosen FET and Fsw is the chosen switching frequency.

    Another thing to consider here is that with your input and output voltages you would need configure it in a buck-boost type of topology. Otherwise when the input voltage goes above the LED stack voltage you will overcurrent the LEDs and maybe damage them.

    Best regards,

    Clint

  • 0 in reply to Clinton Jensen
    Guru 20090 points
    Hello Clint,

    Thank you for the reply.
    Could you please share the design calculator for Buck/Boost and Buck?
    I found Boost Design Calculator only.


    In webench designer, I couldn't simulation on the following conditions due to "RMS input voltage is out of range"

    Vin=4.5V~6.8V
    Vled=3.2V
    ILed=4A

    Could you please let me know this reason?
    When I changed input voltage to 6.8V, I can't simulate it.

    Best Regards,
    Ryuji
  • 0 in reply to Ryuji
    TI__Mastermind 25500 points

    Hello Ryuji,

    I am not sure why it will not simulate in webench. Perhaps the buck-boost isn't enabled in webench yet?

    In any case I do not think there is a buck-boost calculator that is available. But you can use the boost calculator for buck-boost. Just enter the input voltage for VIN and for Vout use the LED stack voltage plus the input voltage. That will calculate the correct components for a buck-boost.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Guru 20090 points
    Hello Clint,

    Could you please let me know the password of the TPS92691 boost calculator?
    Since the calculator is protected, I couldn't change the equation.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Mastermind 25500 points

    Hello Ryuji,

    The password is: Dallas

    Best regards,

    Clint