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LP8556: Could it lighten 72 LEDs at the same time?

Cindy Chang
Intellectual 2475 points
Part Number: LP8556

Hi team,

We've some application questions about LP8556.

If we only have Vin=5V, 

1. Could the 1pcs LP8556 drive 12 series*6 strings = 72 LEDs to light up simultaneously and continuously?

2. Could all the 6 strings of currents be individually set with different current values? (by i2c)

3. Are all the maximum LED current of 6 strings 25mA?

Thank you.

  • 0
    TI__Mastermind 22745 points

    Hi Cindy,

        1. It depends on the current for each string, how about the current if you want to light up at the same time.

         2. No, LP8556 is a global LED driver which means all channels need to be configured with the same current.

         3. The maximum current for each string is 50mA, you can configure it through the I2C.

    BR

    Sean

  • 0 in reply to Sean Zhou
    TI__Intellectual 2475 points

    Hi Sean,

    Thanks for your reply.

    We hope to light up 12 LEDs per string at the same time.

    Here's the spec of our LED.

    Could LP8556 light up 72 LEDs continuously at the same time?

    Thank you.

    Best Regards,

    CindyGW JCLPS2.EM (GEN 2)_EN.PDF

  • 0 in reply to Cindy Chang
    TI__Mastermind 22745 points

    Hi Cindy,

         Quick calculation and estimation, it can support 20mA per channel to light up the all 72 LEDs at the same time, if the current is over 20mA, it may trigger the current limit and trigger OCP protection. So what's the target current?

    BR

    Sean

  • 0 in reply to Sean Zhou
    TI__Intellectual 2475 points

    Hi Sean,

    I'm confused that why over 20mA will trigger OCP but you mentioned max current is 50mA each string.

    The LED needs at least 10mA to light up.

    In conclusion, if we want to light up 72 LEDs at the same time, the current of each strings could not greater than 20mA, right?

    Thank you.

    Regards,

    Cindy

  • 0 in reply to Cindy Chang
    TI__Mastermind 22745 points

    Hi Cindy,

        50mA is the spec for the current, but all spec is related to the detail application, for LP8556, it has an internal MOSFET which will be protected when the current through this FET. So for Vin=5V, and 72LED, each channel will have about 12LEDs, 20mA output current is ok. But for higher output current, it will trigger the internal current limit.

        You may read the LP8556 datasheet to understand it deeply.

    BR

    Sean