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TXS0108E: I2C Level Shifting Issue

Part Number: TXS0108E
Other Parts Discussed in Thread: PCA9306

Hi team,

My customer told me that TXS0108E I2C communication stops with the configuration bleow.

It worked with the only PCB①.

But when connecting ② and ③ boards together, the I2C stopped communicating at the unexpected timing. With connecting 3 boards to the host, I2C commucation stopped with after only one access.

Even when connecting 4.7kOhm pull up resistor after PCA9306, the issue above was not resolved.

Could you please tell me things below?

1. Is TXS0108E configuration is OK? Do you see any problem?

2. Do I need to recommend other level shifter without one shot accelerator?

3. What do you think the potential cause of the I2C communication issue?

Regards,

Itoh

  • Section 9.3.3 of the datasheet says:

    TI recommends careful PCB layout practices with short PCB trace lengths to avoid excessive capacitive loading and to ensure that proper one-shot triggering takes place. PCB signal trace-lengths should be kept short enough such that the round trip delay of any reflection is less than the one-shot duration. […]
    Both PCB trace length and connectors add to the capacitance of the TXS0108E output. Therefore, TI recommends that this lumped-load capacitance is considered in order to avoid one-shot retriggering, bus contention, output signal oscillations, or other adverse system-level affects.

    To be able to handle long cables, use a level-translating I²C repeater.

  • Hi Clemens,

    Thank you so much for your help!

    Regards,

    Itoh