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Request to suggest suitable buffer

Madhu Sharma
Expert 2915 points
Other Parts Discussed in Thread: SN74HC241, SN74LVT16245A, CD74HC243, TXB0104, SN74AVC4T774, SN74LVT16245B

Hi,

I need a buffer with 8 lines, with  2 groups of 4 lines each. Both the group directions should be controlled by separate direction control line (Please refer below image).  I request you to suggest a suitable buffer for this configuration ( preferably small packages lilke TSSOP, QFN or BGAs).

Regards

Madhu

  • 0
    Guru 287860 points

    Bidirectional buffers are only available as voltage translators. However, as far as I can see, none of them has the required configuration.

    It should be possible to combine two unidirectional buffers; the SN74HC241 has one inverting and one non-inverting OE input, which should match with your DIR signals.

  • 0 in reply to Clemens Ladisch
    Expert 2915 points
    Hi,

    Thanks for the reply.

    I need a buffer with properties same as SN74LVT16245A, but with 8 bits, divided into 2 banks ( 4 lines in each bank), operating at 3.3V.

    Please let me know if you need any more inputs for proper buffer selection.

    Regards
    Madhu
  • 0 in reply to Madhu Sharma
    Guru 287860 points

    There is no single device with these properties.

    Use two SN74HC241‍s, or two CD74HC243‍s.

  • 0 in reply to Clemens Ladisch
    Expert 2915 points
    Hi,

    Thanks for the reply.

    Can I use any translators ( like, SN74AVC4T774 or TXB0104) ?

    If yes, is there any translators with Ioh= 32mA and Iol=64mA?

    Regards
    Madhu
  • 0 in reply to Madhu Sharma
    Guru 287860 points

    Thank you very much for keeping the required drive strenth a secret.

    64 mA at 3.3 V requires that you combine at least three outputs for one bit. So, SN74LVC32245.

    What is the actual problem you're trying to solve?

  • 0 in reply to Clemens Ladisch
    TI__Guru 59160 points
    Thank you , Clemens , for all your suggestions to find the right solution for Madhu.
    If I could add , sn74LVT16245B can be considered. It has higher drive strength than LVC devices and have 2 direction control bits. As you rightly mentioned , the DIR control is present for bidirectional transceivers.
    www.ti.com/.../sn74lvt16245b.pdf
  • 0 in reply to ShreyasRao
    Expert 2915 points

    Hi Shreyas,

    Actually I require a buffer to drive 8 gpio lines from a FPGA, connecting to a VME connector. Out of 8 lines, 4 should be controlled with one DIR line and other 4 with other line ( Please refer first figure below). Since this kind of buffer is not available, I am planning to use two level translator ICs instead of one ( Please refer second figure below). Since I am connecting the lines to a connector, drive strength must be atleast 12mA ( all GPIO inputs and outputs are 3.3V level)

    I prefer some 20-TSSOP or smaller packages ( even smaller BGAs are fine) since there is a space constraint in the board.

    Regards

    Madhu