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TCA9803: The configuration with SN74LV4052A

Hirotaka Matsumoto
Guru 27575 points
Part Number: TCA9803
Other Parts Discussed in Thread: TCA9546A, SN74LV4052A

Hi all

Would you mind we ask TCA9803?

Please refer to the attachment file.
20181102_TCA9803.pdf
The customer would like to configure this construction.
We assume that this is possbile.


Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Guru 62920 points
    Hello Matsumoto-san,

    May I ask why TCA9803 is used here? Is it to buffer the I2C signals so that they can drive a higher capacitive load? (I ask because it doesn't look like voltage translation is needed.)

    Anyway, I do see one issue with this connection. Since the "B" side of the device uses current measurements to determine the proper detection of data flow, it is recommend to not use external pull-up resistances (or other sources of pull-up current) in addition to the internal pull-up current source. You can refer to Section 9.4.1.2.1 of the datasheet for further details on this. Would it be possible to remove the pull-up resistances on the "B" side in this application?

    Also note that you may consider use of an I2C multiplexer rather than a standard analog multiplexer, since these devices would allow for configuration via the existing I2C bus and would not require additional GPIO controls for channel selection. An example of such a device would be TCA9546A. Figure 18 in the TCA9803 datasheet shows an example connection between the TCA9803 and an I2C multiplexer.

    Regards,
    Max Robertson
  • 0 in reply to Miguel Robertson
    Guru 27575 points

    Max san

    Thank you so much for your reply!

    May I ask why TCA9803 is used here? Is it to buffer the I2C signals so that they can drive a higher capacitive load? (I ask because it doesn't look like voltage translation is needed.)
    ->The length between Master and Slave units is 1m. So, our customer would like to use bus repeter and multipexer.

      An example of such a device would be TCA9546A..
    ->Of course, we recommend that the customer should use TCA9546A, -44A or 45A instead of TCA9803 with SN74LV4052A.
       The customer would like to switch slaves using IO signal.
        When they use I2C switchs, it occurs delay as follows;
        I2C command -> changing the channel -> I2C command -> Slave transmit -> ・・・・・

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Guru 62920 points
    Matsumoto-san,

    Thanks for the additional information. That all makes sense to me. Please let me know if you have any additional questions.

    Regards,
    Max