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TXS0102: Multiple I2C devices

Peter Szilagyi
Prodigy 150 points
Part Number: TXS0102
Other Parts Discussed in Thread: TCA9509

Hi,

In the datasheet it is mentioned that "It should be used in a point-to-point topology for interfacing devices or systems operating at different interface voltages with one another.".

Does this mean that only one I2C device can be used on each side of the translator IC, or regular I2C bus topologies can be accepted too? For example a master on the 1v8 side and several slaves on the 3v3 side.

Thank you in advance!

Greetings,
Peter

  • 0
    TI__Mastermind 45675 points

    Hi Peter,

    The issue with having several devices on the bus is the added capacitive loading that comes with them. It's recommended to keep capacitive loading to a minimum or there could be issues with the internal edge accelerators of the TXS0102. Thus, it is recommended for a point to point topology. This doesn't mean the device wouldn't be capable of doing so, if you can maintain capacitive loading under 70 pF the edge rate acceleration circuit shouldn't have issues. Another thing to be cautious for in this scenario is the added chance for bus contention. Normally, I2C doesn't have this concern since its an open-drain interface, however with the edge rate accelerator this can be damaging if a device tries to pull the line low during the one-shot pulse for rising edges.

  • 0 in reply to Dylan Hubbard
    Prodigy 150 points

    Hi Dylan,

    Thank you for the well detailed explanation.

    Is this the case with TCA9509 as well, or that is able to handle multiple devices on one output?

    Greetings,
    Peter

  • 0 in reply to Peter Szilagyi
    Guru 316440 points

    The TCA9509 has buffers designed for many I²C devices, and allows the B-side bus to have the full capacitance of 400 pF.