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SN74LVC244A: MDC/MDIO Buffer for 1.2V operation

user4979899
Expert 3080 points
Part Number: SN74LVC244A
Other Parts Discussed in Thread: SN74AUCH244, SN74AUC244, TXS0108E, LSF0108

Hi Sir,

We are looking for MDIO/MDC buffer and operation in 1.2V, SN74LVC244A can meet the request but can't operation in 1.2V,

Could you please help to recommend which part is suitable for the application?

Below is the additional requirement from customer.

How about SN74AUCH244? please advise.

Thanks

1.      Open drain buffer is not recommended for MDC

2.      MDC/MDIO skew caused by the propagation delay should also be examined.

  • 0
    TI__Mastermind 44640 points

    Hi Anne,

    The SN74AUC244 would be a good fit as it will have very low propagation delay and channel to channel skew. I would only use the SN74AUCH244 if the customer needs the Bus Hold feature.

  • 0
    TI__Guru 58200 points
    Hi Anne,

    Do you need buffering capability for the MDC (clock) only or considering it for both the MDIO and MDC?
    The MDIO is open drain and bidirectional signal, so a unidirectional buffer like the LVC244 or the AUC244 may not work for the MDIO.
    The MDC being push pull signal and unidirectional, it should be fine using the LVC/AUC device.
    The TXS0108e supports 1.2V on Vcca but not on the Vccb channel. It is not a true buffer, but a passive translator device with oneshot accelerator circuitry providing momentary AC drive.
    Please let us know what is the purpose of the buffer here? what are the operating voltages on the host / receiver sides? Do you need 8 channel device?
  • 0 in reply to ShreyasRao
    TI__Guru 58200 points
    Anne,

    You might have to look into the I2C buffers / repeater devices, but I see that all of them are not high speed devices. the max freq supported is 1Mhz, for the 2 channel MDIO interface.

    www.ti.com/.../products.html&sort=p2913min;asc
  • 0 in reply to ShreyasRao
    TI__Expert 3080 points

    Hi Shreyas,

    Do you means SN74AUC244  may not a suitable solution for MDIO/MDC?

    We need a device like a buffer which can support 1.2V on both VrefA and VrefB.

    And Yes, we need to support 8 channels. below is the application block.

    FYI. Please let me know which part is suitable for this application.

    Thanks

  • 0 in reply to user4979899
    TI__Guru 58200 points
    Hi Anne,

    No, its not suitable to use sn74AUC244 device, even though it supports 1.2V node, and the 20Mhz speed, it cannot support bidirectional signal lines which the MDIO interface needs.
    consider using the LSF0108 with strong pullups about 250-330ohm with low cap loading at the output.