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TPS61500: LED Driver LCD Brightness Issue

Chandan Kumar2
Prodigy 170 points
Part Number: TPS61500

Hi team,

I am using TPS61500PWPR part number for Controlling LCD Brightness. Could you please confirm what could be the LCD Brightness when we will give Zero input voltage to the PWM Signal in Analog Dimming Mode? Whether LCD will some Minimum Brightness or it will be fully off?
In the earlier Design, I have used TPS61194PWPRQ1 part; where LCD was getting off when we are making PWM Input signal as 0V (logic-Low) and it was giving maximum brightness when we are making PWM Input signal as 3.3V (Logic High).

Our Requirement is LCD should have Minimum brightness when we give PWM signal as 0V, Input voltage max= 16V, output voltage >28V, current sinking >=100mA.

Could you please check the above selected part whether it will meet our requirement or not. If not, could you please share any alternate part for the same requirement.

Please let me know if any other inputs are required.

Thank you

  • 0
    TI__Mastermind 22745 points

    Hi Sir,

     I'm a little confused about your requirement, there should be no current through LED when the PWM=0.

    Regards

    Sean

  • 0 in reply to Sean Zhou
    Prodigy 170 points

    Dear Sir

    In the Earlier Design, we were using "BIT3251 PWM Controller" where the LCD Backlight Functionality is as follows:

    The  "BIT3251 PWM Controller" IC Supports 

    when Enable signal is Low (<0.8V), the device will go into Shutdown state and when Enable signal is High (>1.2V), the device will be active mode.

    when PWM (INN) signal is Low, the LCD is having Maximum Brightness and when PWM (INN) signal is High, the LCD will have minimum Brightness ( The LCD will not go off, it will have some brightness)

    We want to replace this IC with alternate part. Could you please suggest the alternate Part.

  • 0 in reply to Chandan Kumar2
    TI__Mastermind 22745 points

    Hi Kumar,

        It seems negative logic for the PWM signal? Usually for our devices, when PWM signal is high, it output the maximum current and when PWM signal is low, it outputs zero current. So maybe it need a invert logic to convert the control signal.

    Regards

    Sean

  • 0 in reply to Sean Zhou
    Prodigy 170 points

    Dear Sir

    As per the earlier design, we were using (BIT3251) IC, where we were getting minimum brightness when PWM Signal is High and Maximum Brightness when PWM Signal is Low.

    But in case of TI components what I have used (TPS61194PWPRQ1 ) IC, I was using digital Dimming in which if we give PWM Input has high, we were getting Maximum Brightness and when PWM Signal is zero, LCD was getting off, no current through LCD.

    But we want the functionality as same as previous design, means LCD should not goes off in any of the condition, it should have minimum brightness. Will this part (TPS61500PWPR ) can achieve this functionality.

    Kindly provide your feedback on the same.

  • 0 in reply to Chandan Kumar2
    TI__Mastermind 22745 points

    Hi Chandan,

        No, I'm sorry that TPS61500 can't support this kind of requirement.

    Regards

    Sean