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SN74LVT244B: Is there any problem to use SN74LVT244B like SN74LS243 by external connection?

Kazuya Nakai59
Guru 20100 points
Part Number: SN74LVT244B
Other Parts Discussed in Thread: SN74LS243,

 Hello guys,

 One of my customers wants same function device in SN74LVT series as SN74LS243.

SN74LS243

QUADRUPLE BUS TRANSCEIVERS

http://www.ti.com/jp/lit/ds/symlink/sn74ls243.pdf

 The customer couldn't such function (4bit tranceiver IC) in LVT series.

So they are considering using SN74LVT244B with external connecting 1Yn to 2An,

and connecting 2Yn to 1An.

  Their questions are the followings.

Q1.  Is there any problem to use SN74LVT244B like SN74LS243 by external connection like the above?

Q2.  Do you have any 4bit tranceiver IC in LVT series?

 Your reply would be much appreciated.

 Best regards,

 Kazuya.

  • 0
    TI__Mastermind 42600 points

    Hi Kazuya,

    There isn't a way to configure the SN74LVT244B to work the same as SN74LS243. If they want a LVT transceiver they will have to go with an octal option.

  • 0 in reply to Dylan Hubbard
    Guru 20100 points

     Hi Dylan,

     Thank you for your reply.

     Shmitt trigger function is not needed for the customer.

     1OE/2OE active level is not concerned.

     They think SN74LVT224B can be used as a 4bit bus transistor with the following conection.

    1. Connect 1A1 to 2Y1.

    2. Connect 1Y1 to 2A1.  1+2= for No.1 of bus tranceiver. 

    3.  Connect 1A2 to 2Y2.

    4. Connect 1Y2 to 2A2. 3+4= for No.2 of bus tranceiver. 

    5. Connect 1A3 to 2Y3.

    6. Connect 1Y3 to 2A3. 5+6= for No.3 of bus tranceiver. 

    7. Connect 1A4 to 2Y4.

    8. Connect 1Y4 to 2A4. 7+8= for No.4 of bus tranceiver. 

     Is their thinking wrong?

     Are these connections wrong for 4 bit bus tranceivers?

     Could you please tell me what problem is in this connection (solution)?

     Thank you again and best regards,

     Kazuya.

  • 0 in reply to Kazuya Nakai59
    Guru 243120 points

    This would work. It would result in the same circuit as in a standard transceiver, but you have to control the OEs in a different way.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 42600 points

    Hi Kazuya,

    Sorry I was talking in terms of functionality. The buffer won't allow you to dynamically change directions of each channel, but also there will bus contention on every transition due to propagation delay if you configure it this way. Also I'd take caution with the OE pins as to not cause any of the inputs to be floating if they plan on utilizing inputs.

  • 0 in reply to Dylan Hubbard
    Guru 20100 points

     Hello Clemens, Dylan,

     Thank you very much for your reply.

     Your reply is very helpful for the customer and me.

     Thank you again and best regards,

     Kazuya.