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circuit verification

Vishwajit Vivek
Prodigy 160 points
Part Number: TXS0108E
Other Parts Discussed in Thread: TXB0108, SN74LVC245A, SN74LVC244A

Hi,

I am using a buffer  of this part number "TXS0108EPWR".

My requirement is to use a buffer that can be used as bidirectional buffer. I dont want to do any level translation to my signal & so I have fed 3.3 volts to port A & port B. The direction of signal is not unidirectional. Few signals shall be birectional, few unidirectional, few will receive signal from port A & few will receive signal from port B so kindly check whether my below circuit connection & your part meets my requirement. Also kindly suggest me what needs to be done to unconnected pins.

  • 0
    TI__Guru 62180 points
    Hi Vishwajit,

    The important thing to note on the TXS is that it is not a true buffer device.
    A buffer will provide drive strength to the signal, isolate the input signal from loading due to high input impedance at the input of the buffer.
    What is the bufferring requirements in terms of loading / drive strength required.
    TXB0108 provides a minimal 20uA drive strength which is again for interfacing into high impedance loads.
  • 0 in reply to ShreyasRao
    TI__Guru 62180 points
    For unidirectional signals, a true buffer like SN74LVC244A or the SN74LVC245A transceivers(DIR controlled bidirectional buffer) can be used.
  • 0 in reply to ShreyasRao
    Prodigy 160 points
    I am using this buffer to isolate the signals coming from backplane to the FPGA & signals going from FPGA to backplane. Apart from the drive strength requirement is there anything else that you think will not work in my circuit?
  • 0 in reply to Vishwajit Vivek
    TI__Guru 62180 points

    Vishwajit,

    The TXS is not classified as a true buffer, rather it is a switch based design. The internal FET passes the signal when turned on( switch) and when FET is off, the other side is held high through the pullup resistor.

    True buffers like the SN74LVC/ SN74AVC can drive low or drive high, sink and source current into or out of the device.