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LP8865Y-Q1: Internal Soft Start to Dimming Mode startup sequence

Chun-Ju Wu
Prodigy 40 points
Part Number: LP8865Y-Q1

Tool/software:

Hi Team,

I have some questions about the Dimming Mode of the LP8865

1. During power-on, when the EN PIN is pulled high, it will take at least 100 us to enter the dimming mod. How long will it take to exit the dimming mod? Or will it not start operating until the EN/PWM Pin and ADIM/HD Pin act correctly?

2. POR = Power-On Reset? 

3. How long will the POR last?

4. Assume that the LP8865 is operating and running in PWM Dimming mode. If Internal Soft Start is required, EN/PWM must be low for a few seconds before being high for more than 5us?

 

Thanks.

  • 0
    TI__Mastermind 22405 points

    Hi, Chun-Ju

    1. During power-on, when the EN PIN is pulled high, it will take at least 100 us to enter the dimming mod. How long will it take to exit the dimming mod? Or will it not start operating until the EN/PWM Pin and ADIM/HD Pin act correctly?

    Correct, once it enter the dimming mode, it will not exit the dimming mode.

    2. POR = Power-On Reset? 

    3. How long will the POR last?

    POR is related with the VDD threw rate if EN is always high. Once it reaches VIN_UVLO, it will start POR. POR is power on reset. If EN is after the VDD, it will POR 200us after the EN is high.

    4. Assume that the LP8865 is operating and running in PWM Dimming mode. If Internal Soft Start is required, EN/PWM must be low for a few seconds before being high for more than 5us?

    5us high is used to enable the device, and if you want a low brightness for startup, it needs to change to low duty after 5us.