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LP8863-Q1: Using Analog signal for dimming control

Alonso Jimenez
Prodigy 200 points
Part Number: LP8863-Q1

Hello,

I'm looking for Led-backlight Driver to be used in a new design and LP8863-Q1 may be a good option. I would like to use an analog signal to control the dimming of the leds.

Will be possible to do it using the LP8863-Q1 on PIN SDO-PWM? I know that some chips that use PWM for control dimming implement a LPF on PWM input to generate an analog voltage but I don't know if this is the case of the LP8863-Q1. If this is not the case, could you please advice other TI chip that may be used in that way?

Best regards and thanks in advance

   Diego

  • 0
    TI__Genius 11836 points

    Hi Alonso,

    Yes. You can input PWM through this pin to achieve analog dimming.(in Hybrid dimming mode and set the PWM and current modes transition threshold at 0% brightness with the DIMMING_MODE bits)

  • 0 in reply to Charles-Chen
    Prodigy 200 points

    Hello Charles,

    Thanks for your reply.

    I would like to clarify my question in order to be sure. I would like to control de dimming using an analog voltage signal voltage, [0 to 3V3]. That means:

    - 0V dc --> 0% brightness

    - 1.65 --> 50% brightness

    - 3v3 --> 100% brightness

    Could you please confirm that this can be possible by using only the PWM pin?

    Best Regards

        Diego

  • 0 in reply to Alonso Jimenez
    TI__Genius 11836 points

    Hi Alonso,

    You can only achieve analog dimming by PWM signals. That means:

    - 0% duty cycle --> 0% brightness

    - 50% duty cycle  --> 50% brightness

    - 100% duty cycle --> 100% brightness

  • 0 in reply to Charles-Chen
    Prodigy 200 points

    Hi Charles, 

    Could you please advice other component from TI catalog that may be used to dimming the brightness using analog signal as required? e.g.:

    - 0V dc --> 0% brightness

    - 1.65 --> 50% brightness

    - 3v3 --> 100% brightness

    Best regards and thanks

        Diego

  • 0 in reply to Alonso Jimenez
    TI__Genius 11836 points

    Hi Alonso,

    What's your other specific requirement of the chip? For example, the input voltage range, output current of each channel, and so on.

  • 0 in reply to Charles-Chen
    Prodigy 200 points

    Hi Charles,

    - Input voltage range--> we can generate whatever necessary and thus not very restrictive. For example 12V, 5V will be valid.

    - Output current --> 150 mA as LP8863-Q1 will be valid

    - Output voltage --> Up to 40 

    - Number of led strings --> 6. 4 may be valid.

    How can identify the TI chips that can be controlled by Analog signal? Hoy do you identify it?

    Regards

        Diego

  • 0 in reply to Alonso Jimenez
    TI__Genius 11836 points

    Hi Alonso,

    Sorry. I have checked with my team and there are no dedicated analog pin for our device in my team temporarily. Maybe you can try to change the voltage on ISET pin by analog voltage input instead.

    • How can identify the TI chips that can be controlled by Analog signal? Hoy do you identify it?

    Just through datasheet of device.

    May I ask a question why analog input is mandatory in your system?

  • 0 in reply to Charles-Chen
    Prodigy 200 points

    Hi Charles,

    Thanks for your fast reply.

    We have decided to use the LP8863-Q1 and implementing an adicitional analog to PWM conversion. 

    We need tu use analog control due to qualification requirements.

    Best regards and thanks

        Diego

  • 0 in reply to Alonso Jimenez
    TI__Genius 11836 points

    Hi Alonso,

    I would appreciate if you could provide more details about the qualification requirements. What's the negative effect about the PWM control signal? Your information is important for us when developing new devices.