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TSB81BA3E: Interface to 1.8V Controller

Johannes Burke
Prodigy 50 points
Part Number: TSB81BA3E
Other Parts Discussed in Thread: SN74AXCH8T245, TXB0304, TXB0108

Hello,

since long we use the TSB81BA3E together with a FPGA, which harbours the controller . The bus interface was completely 3.3V

For a new FPGA, which has a 1.8V only bus-interface, we have to redesign the application.

I think some kind of level-shifter is neccessary, probably with automatic direction usage.

Or could we use some kind of capacitor-coupled interface?

Could anyone give some recommendation about this, possible which interface chips to use?

Regards,

Johannes Burke

  • 0
    TI__Mastermind 35130 points
    Hi Johannes,

    We'll look into this and get back to you soon.

    Regards,
    I.K.
  • 0
    TI__Guru 62440 points
    hi Johannes,

    So to understand the application more, please provide me the details regarding:

    1) Signal direction : Unidirectional or Bidirectional
    2) Data rate or Frequency desired.
    3) I assume the signals are push pull and not open drain, but please confirm.
    4) Is there a standard interface protocol being used? SPI, UART etc.

    We have options in both the auto bidirectional or Dir controlled devices, but these information requested above will help narrow it down further.
  • 0 in reply to ShreyasRao
    Prodigy 50 points

    Hi Shreyas

    the answers to your questions:

    To 1) The signal direction is bidirectional,

    To 2) The data rate is 100 Mbps

    To 3) Yes the signals are push-pull.

    To 4) It’s no standard like SPI, UART. The TSB81BA3E is a FireWire Transceiver from Texas Instruments.

     

    Regards.

    Johannes

  • 0 in reply to ShreyasRao
    Prodigy 50 points
    Hi Shreyas,

    additional remarks concerning the signal direction:
    There are bidirectional and unidirectional signals to be translated.
    The unidirectional signals are no problem and a voltage level shifter can be found.
    But the bidirectional signals have a relative high data rate. These are 8 data-bits and 2 control lines.
    On the TSB81BA3E these signals have a 'bus holder' functionality. Could this possibly lead to another
    way to shift the voltage level? At TI application notes are available, that show the use of bus-holder functionality
    to do galvanic isolation between a FireWire Phy and LLC.
    Could a similar method also lead to voltage level shift, although one side has no built-in bus-holders?
    Possibly by adding a termination IC, which has bus-holder functionality?

    Regards,
    Johannes
  • 0 in reply to Johannes Burke
    TI__Guru 62440 points
    Hi Johannes,

    We have recently released SN74AXCH8T245 device which supports bus hold(H indicates bus hold feature) on the IO channels, it supports 1.8 to 3.3V or vice versa bidirectional translation using a DIR control pin. It supports and exceeds 100Mbps data rate at this voltage.
    Let me know if this would work.
  • 0 in reply to ShreyasRao
    Prodigy 50 points
    Hi Shreyas,

    unfortunately there is no direction control in my application. So the transceiver needs to support auto-direction sensing.

    Regards,
    Johannes
  • 0 in reply to Johannes Burke
    TI__Guru 62440 points
    Hi Johannes,

    In that case, I would recommend using the TXB0304 which is 4 channel auto directional translation device which can support 100 Mbps.
    For 8 channels, there is TXB0108, but achieving data rate of 100 Mbps may be an issue.
    Please let me know if these devices would be suitable for your application.
  • 0 in reply to ShreyasRao
    Prodigy 50 points
    Thanks Shreyas, I think this part could solve the problem.