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DP83848J: DP83848JSQ/NOPB

Su Franket
Prodigy 10 points
Part Number: DP83848J

We used IC DP83848J on the current design and got issue on pin feature RXD_3/PHYAD4.

In the SPEC suggestion, we need to add external pullup resistor 2.2k ohms for PHY Address strapping change.

Based on the measure, the pin RXD_3/PHYAD4 will change to low impedance after IC configure down and cause voltage level to 1.7V.

Does it met except result ?

By the way, the external resistor will have limitation as 2.2K ohms or we can use 22K ohms for it ?

  • 0
    TI__Genius 12295 points

    Hi Su,

    Su Franket said:

    We used IC DP83848J on the current design and got issue on pin feature RXD_3/PHYAD4.

    In the SPEC suggestion, we need to add external pullup resistor 2.2k ohms for PHY Address strapping change.

    Would you be able to clarify what the issue is with the RXD_3/PHYAD4 pins? Is the PHY address you are reading not matching up to your straps?

    Su Franket said:

    Based on the measure, the pin RXD_3/PHYAD4 will change to low impedance after IC configure down and cause voltage level to 1.7V.

    Does it met except result ?

    The 2.2k resistor should be pulled directly to GND or VCC. It looks like from the picture provided that there is another resistor there. 

    Su Franket said:
    By the way, the external resistor will have limitation as 2.2K ohms or we can use 22K ohms for it ?

    We recommend using the 2.2k resistor, otherwise we cannot gurantee device functionality.

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    Prodigy 10 points

    Hi Melissa,

    Melissa Chang said:
    Would you be able to clarify what the issue is with the RXD_3/PHYAD4 pins? Is the PHY address you are reading not matching up to your straps?

    Based on our design, we will strap PHYAD4 pin as address "1" and provide it to other IC at the same time.

    For now, the net voltage level will drop to 1.7V after IC configure down and cause other function abnormal.

    We want to keep this net SN_PKG_ID0 as High (3V) even if IC DP83848J configure down.

    If we don't use RXD_3 feature but PHY address only, can the resistor change to 22K ohms ?

    Thanks.

  • 0 in reply to Su Franket
    TI__Genius 12295 points

    Hi Su,

    The datasheet recommends pulling up the pin directly to 3.3V with a 2.2k Ohm resistor. Any other configurations for this have not been tested or verified for functionality by our team, but you may perform your own calculations or tests for verification.

    You may also leave the pin disconnected to let it go to the default state (it has a weak internal pulldown resistor), but the PHY address cannot be changed through register writes.

    Best regards,

    Melissa