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TXB0304: 1.8/3.3 MDC/MDIO does not work TXB0304

Ilya Teplitsky3
Prodigy 10 points
Part Number: TXB0304


We got 1 board out of 4 working with TXB03034 used for MDC/MDIO lines b/w CPU and PHY. CPU requires 1.5k (MDC) and 4.7K (MDIO) pull up. The buffer translates to 3.3V which connects to the phy chip. Besides the ringing on 3.3V side of the buffer, we observe the incorrect desertion of waveform by the buffer, i.e. clock line doe not stay for full period, which causes the I/f not work. Please note, the NXP CPU LS1043A states that MDIO/MDC I/f can either be used as OD (open drain) or actively driven. We do not use open drain setting in our design.

  • 0
    TI__Guru* 97046 points
    Hi Ilya,
    Do I understand correctly that you have pull-ups attached to the TXB0304? If so, that is likely the source of your troubles. The TXB0304 will not work correctly with pull-up resistors less than 20kohm due to its architecture.

    If you can share a schematic/more details, we can help with the correct translator selection.