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DP83826E: Recommended Crystal Load Capacitance

Conor
Guru 15160 points

Part Number: DP83826E
Other Parts Discussed in Thread: AM263P4, LP-AM263P, DP83869

Hi,

We are designing a board using the AM263P4 and the DP83826E Ethernet PHY. We plan to use a 25-MHz crystal as the reference clock for the DP83826E.

Could you please clarify the following points?

  1. What is the recommended load capacitance and allowable range for the crystal connected to the DP83826E?
  2. Can a crystal with a load capacitance of 6 pF to 12 pF be used?
  3. Is there a recommended crystal circuit or a list of validated crystal part numbers for the DP83826E?

We also reviewed the LP-AM263P evaluation board. However, the calculated load capacitance of its crystal circuit appears to differ significantly from the load capacitance specified for the PHY. Could you explain how the crystal and external capacitors on the evaluation board were selected?

PROC171E2A(001)_SCH.pdf 

Best regards,
Conor

  • 0
    TI__Mastermind 44955 points

    Hello Conor,

    The DP83826 PHY has been characterized to work with load capacitances up to 40pF per datasheet. Xtals with lower capacitance can be used.

    An example xtal circuit for DP83826E is ECS-250-12-33Q-JES-TR, located on our EVM.

    The PROC171 file you provided has a different PHY; DP83869. This has similar requirements as DP83826.

    While you are interested in DP83826, I would like to suggest our latest and greatest device; DP83826A.

    Sincerely,

    Gerome