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DP83848Q-Q1: DP83848Q-Q1 RMII External Reference Clock

Joe Howard
Intellectual 2970 points
Part Number: DP83848Q-Q1

I have a customer that is interested in using an external oscillator for RMII and using it to provide a clock to both the PHY and the MAC.

How should the external oscillator be selected, if it's being used to supply the clock to both the PHY and the MAC (Load Capacitance)?

How should these signals be routed in layout to maximize the signal integrity?

-Joe

  • 0
    TI__Mastermind 23675 points
    Hi Joe,

    What is the setup and hold time of the MAC you are using?
    Also, what is the delay in relation to the reference clock of the MAC you are using?
    The DP83848Q timing is listed in the datasheet. With about 1ns/6inch of prop delay for FR4, we can figure out the best place to locate the oscillator.
    Also, as for load capacitance, the interface is spec'd to 25pF.

    Kind regards,
    Ross