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LP8860-Q1: adaptive mode can't work at display mode

Part Number: LP8860-Q1

When we en adaptive mode and LED work at display mode.

If total LED vf is about 23.1V and boost initial voltage is 30V

Boost voltage should be adjust to 24~25V after LP8860 start-up, right??

But we measure boost voltage is 30 and it can adjust via BOOST_INITIAL_VOLTAGE[5:0]

Is register set error?? or an other problem?

  • Hello,

    there are three reasons for boost not adapting from initial voltage to a lower LED Vf voltage.

    1. LED strings are in cluster mode.

    2. EN_ADAP bit in register 0x72 in EEPROM is 0x0.

    3. Device is configured to vary brightness via PWM- Input Direct Mode AND duty cycle is 100%.

    Other than these three scenarios, I do not see a reason why boost should not adapt to a lower LED Vf. Can you please double check these register settings?

    Thanks,

    Liaqat

  • Hi, Liagqt:

    Thanks for your reply.

    I can make sure LED strings in display mode and EN_ADAP bit is 1

    I will check the brightness control mode and PWM duty, I think it is the root cause in this issue.
  • Hello,
    Since I have not heard further, I will close this thread and hope that enabling EN_ADAP bit or not using 100% duty in direct mode solved this issue. If not, please feel free to open another thread.
    Thank you.
    Liaqat