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LED171596A: Could LED171596A normal work when we setting ILED =10uA?

NObody
Expert 1100 points
Part Number: LED171596A

Sorry to bother.

As the title, customer want to set Iled = 10uA, base on this condition, could LED171596A normal work? 

Other question, what is the minimum Iled value? 

  • 0
    TI__Intellectual 1985 points
    Hi NObody,

    LED171596A is not designed to perform well with such low loading condition.

    Is ISET = 10uA refers to the peak current ? i.e. the current set using RISET? or average current for each LED with PWM at 100%? The difference between these 2 definition is 4X.

    I am also curious, what kind of application you are targeting? LED might not even light up with 10uA.

    Regards
    H L
  • 0 in reply to Hak-Leong Ng
    Expert 1100 points
    Hi, HL：

    Sorry for the late response because of the Chinese New Year's vacation.

    I think customer need average current = 10uA not peak current.

    base on average current, 40uA peak current can normally work on LED171596?
  • 0 in reply to NObody
    TI__Intellectual 1985 points

    Hi,

    I don't know what the application is for, so I am going to reply base on LED application and I am assuming 96 LEDs on a LED71596A.

    There are a few ways to achieve an average current of 10uA for each LED, if this is what the customer desire.

    1. Set peak current (ISET) to 10mA, set master brightness to max (0x1FF); for each LED, set PWM to max (0x1FF) and set current to 0x001. Under this setting, you will have an average current of 10mA/4/255 = ~ 9.8uA. With each step increment of current, you will get an additional 9.8uA until the MAX of 2.5mA average current for each LED. The peak current is about 39uA and on time for each LED is 25%,

    2. Set peak current (ISET) to 10mA, set master brightness to max (0x1FF); for each LED, set PWM to max (0x2) and set current to max 0xFF. You will get the same average current as in case 1, but the peak current in this case is 10mA and the on time is about 0.1%

    The difference between case 1 and case 2 is case 2 is using PWM switching and case 1 is with 100% PWM/. If accuracy is more important, case 2 will be a better choice. .

    With above setting, I observe light on our EVM, very weak, but I can see it.

    Please note that in both case 1 and case 2, the settings are reaching minimum, there is no room to adjust any lower.

    Regards
    H L

  • 0 in reply to Hak-Leong Ng
    TI__Intellectual 1985 points
    Hi,

    If there is no more questions from you. I will close this case.

    Thank you
    H L