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TCA9517-Q1: multiple B-side connection application

Shih Stone
Prodigy 65 points
Part Number: TCA9517-Q1
Other Parts Discussed in Thread: TCA9517, TCA9509

Dear,

Per you datasheet, it seem two B-side port can't connect in serial.

However our application are connect in parallel, we want to confirm can you use TCA9517-Q1 in example circuit(parallel) below.

This example connect two TCA9517-Q1 B side port to the same host.

Is it OK?

And how about paralle three TCA9517-Q1 and connect to the same I2C master??

  • 0
    TI__Mastermind 49270 points

    Hey Shih,

    It would be best if you could design the device such that B side is not in parallel with another B side device. In some cases this can work but I've seen in rare loading conditions when B side is set up in parallel like what you have, the I2C bus can oscillate on the SDA line and cause errors.

    Would it be possible to flip the 9517?

    Do you have an I2C bus block diagram?

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 65 points

    Hi Bobby,

    The I2C concept diagram show as below.

    And the reason we can't flip 9517 is because the max. Vol in 9717 B-side is 0.6V and the end device max. Vil  only 0.4V.

    That means when B-side output more 0.4V, the device will not recognize it.

    Interesting thing is we use TCA9517 as buffer(repeater) to increase driving strength.But it can't be use in parallel. 

    Do you have other suggestion?

  • 0 in reply to Shih Stone
    TI__Mastermind 49270 points

    Hey Shih,

    Sorry for the delay in response, I am currently out of office.

    What is the VccA and VccB levels on both of the 9517s?

    If one of them is 1V higher than the other then it may be possible for use to switch out one of the 9517s with a TCA9509 as the A side of that device has a low VoL and the static offset is on A side instead of B side.

    -Bobby