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TXB0104: current driving capacity

FRANK1
Expert 8925 points

Part Number: TXB0104
Other Parts Discussed in Thread: MAX3232E, SN74LVC1G17

Hi Sir,

I have a query on TI IC: txb0104,

In use, the corresponding output terminals of other ICs connected to its input I/O pin should have a minimum current driving capacity of 2mA, right?
So If we use another TI IC max3232e to connect with it.
Max3232e's maximum output driving capacity is 1mA, right?
So the two ICs can not be used perfectly, right?
Can I add a pull resistor outside the max3232e output port to enhance its current driving ability?

Thanks.

Thanks a lot.

Regards,

  • 0
    Guru 325150 points

    The TXB's inputs are symmetrical; the driving ability is needed for both high and low voltages.

    You could add a buffer, e.g., SN74LVC1G17.

    But RS-232 signals are not bidirectional, so the TXB might not be needed. What directions and voltages do the other signals have?

  • 0 in reply to Clemens Ladisch
    TI__Expert 8925 points

    Hi Clemens,

    Thank you for your reply.
    In fact, I don't want to add a buffer as the driving capacity of one end is not enough.
    In my actual design, only the driving capacity of the receiving end on the side of TXB is not enough,
    that's all.
    So I want to design according to the schematic diagram I sent you.
    I would like to trouble you to check the feasibility.
    I want to pull a resistor on the line to increase the current capacity only.

    I do not want a big change, it's better to use less components.
    Is this possible for my design only add a pull-up resistor?
    Thanks.
    Regards,

  • 0 in reply to FRANK1
    Guru 325150 points

    The TXB does not work with pull-up resistors.

    If ROUT2 is too weak, then you have to add a buffer. It might be a better idea to replace the TXB with a different level shifter.

  • +1 in reply to Clemens Ladisch
    TI__Mastermind 47735 points

    Hey Frank,

    As mentioned by Clemens, the TXB device will not work with pull-ups (unless they are weak). If you don't have enough drive the change the state of the I/O then it will be best to move to a device like the TXU0204 which is p2p. This issue can not be resolved just by adding a pull-up.