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DP83822HF: About timing of reset for stable crystal output

Tao_2199
Genius 5770 points
Part Number: DP83822HF

Hello,

 

Regarding to timing of reset on DP83822, my customer is asking a question.

 

(Question)

They will use external crystal as XI/XO and use external reset from MPU.

When power up, how long should we need to keep for stable crystal output ?

(Please below diagram.)

 


 

Regards,

Tao2199

  • 0
    TI__Mastermind 18425 points
    Hello Tao2199,

    Crystal oscillator stabilization is not characterized. The PHY will take approximately 200ms after power up to sample straps and transition the strap pins to I/O pins. The oscillator will be stable within this time. Can you use this number?

    -Regards,
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    Genius 5770 points

    Hello Aniruddha,

    Thank you for reply.
    I have an additional question.

    About period T3(200ms) in figure1 on page15,
    According to datasheet page11, it is described as following.
    "Hardware configuration latch-in time for power up"

    It is meaning that it's need 200ms for transition the strap pins to I/O pins.
    And the oscillator will be stable within this time
    My understand is correct?

    Regards,
    Tao2199

  • 0 in reply to Tao_2199
    TI__Mastermind 18425 points

    Hello Tao2199,

    That is correct, 200ms is the time need for the PHY to power up, sampled the strap pins, and then transition those pins to normal IO operation. The oscillator would be stable within 200ms of startup if the PHY design requirements are met. But the exact time for oscillator stabilization after power up is currently unavailable.

    -Regards,
    Aniruddha

  • 0 in reply to Aniruddha Khadye
    Genius 5770 points

    Hello Aniruddha,

     

    I informed to my customer and they could understood about strap pins.

    Many thanks!

     

    Regards,

    Tao 2199