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LP8865X-Q1: TFT backlight driver design and calculator requirement

Brian Lin
Prodigy 10 points
Part Number: LP8865X-Q1

Tool/software:

We have a TFT panel backlight driver circuit need to design.

1.The forward voltage range is 30V~36V and its typical forward current is 270mA.

The Vin of driver chip is 4.5V~ 5.5V and the LED backlight circuit is 11 LEDs are connected in series as one group, and there are four groups in parallel.

Is LP8865X-Q1 applicable the backlight circuit? Does the chip's specifications exceed my requirements?

2.Can you share the design calculator to us ? 

Thanks.

Brian

  • 0
    TI__Mastermind 31255 points

    Hi, Brian

    So the output current should be 4*270mA right? consider the 36V output and 4.5V input. The switching current is high and LP8868X cannot support that.

    May I kindly know why they required a 4.5V to 36V, such an tough system.

  • 0 in reply to Zhiqian Wu
    Prodigy 10 points

    Hi Sir:

    1.The total output current is 270mA , is not 4*270mA.

    Becuse We will allow the 12V power system and the 24V power system to coexist., So we will use 5V which is 12V(24V) to 5V buck output to be input of LP8868X.

    If we do not use the 5V to be the input,  use 9V ~ 28V to be  the input of LP8868X and keep the output voltage is 36V and output current is 270mA, Can the LP8868X support this requirement and do not change any components if we change the input from 12V to 24V or from 24V to 12V? 

    2. Please kindly provide the calculator of LP8868X.

    Thank you very much.

    Brian 

  • 0 in reply to Brian Lin
    TI__Mastermind 31255 points

    Hi, Brian

    I will send the email to you for the calculation tool.

    For 270mA total, it can be used as LP8868X.

  • 0 in reply to Zhiqian Wu
    TI__Mastermind 31255 points

    Hi, Brian

    Pls kindly share your email and I will send to you.

  • 0 in reply to Zhiqian Wu
    Prodigy 10 points

    My email address is brian.lin@deltamobile.com 

    Thank you very much.

  • 0 in reply to Zhiqian Wu
    Prodigy 10 points

    Hi Sir:

    Thank you for your reply.

    1.If we do not use the 5V to be the input,  use 9V ~ 28V to be  the input of LP8868X and keep the output voltage is 36V and output current is 270mA, Can the LP8868X support this requirement and do not change any components if we change the input from 12V to 24V or from 24V to 12V? 

    2.Because all of the equations do not mention Vin(min). Do we only take care Vin(max)?

  • 0 in reply to Brian Lin
    TI__Mastermind 31255 points

    Hi， Brian

    1.If we do not use the 5V to be the input,  use 9V ~ 28V to be  the input of LP8868X and keep the output voltage is 36V and output current is 270mA, Can the LP8868X support this requirement and do not change any components if we change the input from 12V to 24V or from 24V to 12V? 

    Depending on 36V output, it is fine.

    2.Because all of the equations do not mention Vin(min). Do we only take care Vin(max)?

    For boost, VIN min is required for the design.