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LMKDB1104: PWRGD/PWRDN# configuration

Hailiang Zhang
Expert 7525 points
Part Number: LMKDB1104

Tool/software:

Hi Expert,

Customers want to know if PWRGD/PWRDN# can be directly connected to a high level? They do not need the PG function. If it cannot be directly connected to a high level, how long is it recommended to pull PWRDN# high after PG?

Regards，
Hailiang

  • 0
    TI__Mastermind 22861 points

    Hi Hailang, 
    Not exactly. 
    PWRGD needs a low-to-high clk transition to start up the device. 
    After this first transition the pin functions as normal power down pin (active low). 

    So, in theory - as long as your CLKIN is available before this then yes you can tie PWRGD/PWRDN# directly to VDD. 

    Just ensure CLKIN is available before VDD in this case given you PWRGD/PWRDN# pin requires it's asserted after CLKIN is available. 

    Best regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Expert 7525 points

    Hi Vicente,

    It sounds like I can connect PWRGD/PWRDN# directly to VDD if CLKIN is before VDD. If CLKIN is after VDD, then I can't. Is that correct?

    Also, given that PWRGD/PWRDN# transitions from low to high after VDD and CLKIN to start up the device, connecting PWRGD/PWRDN# directly to an external 3.3V Aux before CLKIN is not a good idea, right?

    Regards,
    Hailiang

  • 0 in reply to Hailiang Zhang
    TI__Expert 7525 points

    Hi Vicente,

    One more question, vPWRGD is a input pin, customers need to actively pull this pin from low to high to start the device after VDD and CLKIN are valid, right? How long after being pulled high does this pin work as PWRDN#?

    Regards,
    Hailiang

  • 0 in reply to Hailiang Zhang
    TI__Mastermind 22861 points

    Hello Hailang,

    Sorry for the delay I am out of office on vacation.

    That is correct - ensure CLKIN is available before VDD.

    The pin works immediately after the first low to high transition as PWRDN# - it’s just that first initial low to high transition with CLKIN that’s required. 
    I will have another AE assist you from here on out.

    Beat regards,

    vicente