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TXB0104 connected to each other and high impedance drivers

jean-francois hasson
Prodigy 30 points
Other Parts Discussed in Thread: TXB0104

Hi,

We could have the following setup :

Driver/Receiver A  <---------------> TXB0104 A <------------------> TXB0104 B <------------------------> Driver/receiver B

In this setup, Driver/Receiver A and driver/receiver B are for several seconds in a high impedance state after a power up. The TXB0104 are enabled and after a few seconds the  drivers/receivers on both sides will be configured as one driver and one receiver.

The question is what is going on when both driver/receivers A and B are in high impedance ? What happens if for some reason the voltage level between Driver/receiver A and TXB0104A is equivalent to a logic high and the voltage level between Driver/receiver B and TXB0104B is equivalent to a logic low ? Will there be a conflict ?

Best regards,

 

JF Hasson

  • 0
    TI__Genius 9085 points

    I am not sure I understand your configuration. You have 1 TXB device?

    The TXB is a buffer device, and will settle to a high or a low, even if the A and B sides are high impedance.

    There will be no contention, unless A and B sides are being actively driven by a HIGH on one side and a LOW on the other side.

    You could avoid any possible contention by disabling the device (keep OE low) until the drivers/receivers are configured.

  • 0 in reply to Hattie
    TI__Genius 9085 points

    Looking at the post title again, it seems like you are using 2 TXB.

    I am not sure this configuration will work.

    Why are you using 2 of the devices instead of 1?

  • 0 in reply to Hattie
    Prodigy 30 points

    Hi,

    We could have this configuration because we are using COTS boards where some discrete signals are routed through TXB0104 buffers. We would have two of these COTS boards exchanging discrete signals potentially directly so we would have the configuration I tried to explain above. We are wondering if we need to put an isolation buffer between the two COTS boards on the discrete signals and enable this buffer only when the driver/receiver A and B are configured (ie one an in and the other one an out). Which do you recommend and why ?

    Best regards,

    JF Hasson

  • 0 in reply to jean-francois hasson
    Prodigy 30 points

    Hi,

     

    Any feedback regarding why this configuration may not work ?

     

    Best regards,

     

    JF Hasson

  • 0 in reply to jean-francois hasson
    TI__Genius 9085 points

    Hello Jean-francois,

     

    Sorry for the delay. 

     

    The TXB device has an internal 4kOhm buffer/driver. One TXB device would have trouble 'over-powering' another TXB device because they would have a similar drive strength.

    However, the TXB devices also have edge acceleration 'one-shot' circuity. I think that this edge acceleration circuitry would help one TXB device overpower the buffer in another TXB device but I may need to collect some data to verify this.