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TCA4307: Does adding a TCA4307 on host part improve the maximal length of cable ?

Charles SALMON
Prodigy 60 points
Part Number: TCA4307
Other Parts Discussed in Thread: TCA9800

Hello,

I have a host with an I2C master that will be connected to an I2C slave device.

I want to use the TCA4307 on slave side to benefits of the hot swap feature.

Should I use a TCA4307 on the host part as well ?

From my understanding, it wont improve the maximal length of the cable ; but in the Figure 9-2 of the datasheet, it says 'Long distance bus' between the two TCA4307.

What should I do ?

Thanks,

Charles

  • 0
    Guru 287110 points

    Section 9.2.1.1 describes what you must care about if you have two buffers. This does not imply that you would always want to have two buffers.

    How long is your bus? How weak is your master? If you really need a buffer at the host, you can choose one without hot-pluggin features (e.g., TCA9800).

  • 0 in reply to Clemens Ladisch
    Prodigy 60 points

    The length between the host and the device should not exceed 2 meters.

    The host is an ESP32, 3.3V. And there are two I2C chips on the host side. I am not sure of the power of the I2C coming out from the ESP32, I would say some mA.

  • 0 in reply to Charles SALMON
    Guru 287110 points

    All devices must have enough drive strength for the entire bus (segment). The ESP32 is certainly strong enough.

    All I²C devices must support at least 3 mA. When sizing the pull-up resistors for higher currents, it is possible to use higher speeds.

    Using a buffer like the TCA9800 makes sense if some devices are weaker than 6 mA, and if you want higher speeds.