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TCA9511A: TCA9511A multi-master capable?

user1640887
Prodigy 40 points
Part Number: TCA9511A
Other Parts Discussed in Thread: PCA9515A, TCA9517A

Tool/software:

Hi,

I am planning to use TCA9511A.

TCA9511A multi-master capable?
I'm checking whether the following configuration is possible:

                            TCA9511A                  TCA9511A
I2C Master1 ----- I2C IN OUT------------ I2C OUT IN ---- Slave Device
                                                     |
I2C Master2 ----- I2C IN OUT-------
                                                     |
I2C Master3 ----- I2C IN OUT-------
                                                     |
I2C Master4 ----- I2C IN OUT-------

EN pin is assumed to be always active and has a proper pull-up.
Please let me know if there are any configurable devices.

Also, please let me know if there are any configurable devices.

best regards,

  • 0
    TI__Guru 50688 points

    Hello,

    I need more information on what is required in multi-master systems? Do masters 1-4 expect that TCA9511A will handle flow control or deal with arbitration in the address? I know I2C is open-drain, during the send of the address, the masters will have to determine which master wins priority of the bus via lowest 7-bit address. Is this integrated in each of the masters? What is the expectation from the TCA9511A? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 40 points

    Tyler-
    Thank you for your reply.

    I don't expect the TCA9511A to perform flow control or address arbitration.
    Each I2C master has multi-master functionality.
    Since the wiring between the master and slaves is far apart, I use the TCA9511A for waveform shaping.
    The functions I'm expecting from the TCA9511A are as follows:

    - Can the TCA9511A be used in a multi-master environment?
    - Is it possible to connect TCA9511As in series or in parallel?
    - When connecting TCA9511As in series, is it okay to connect the OUT terminals together?

    Some devices, such as the PCA9515A, cannot be connected in series, but I believe it is possible with the TCA9511A.

    best regards,

  • 0 in reply to user1640887
    TI__Guru 50688 points

    User1640887,

    TCA9511A "OUT" side does not detect the stop-bit / idle detection so connecting "OUT" sides in parallel is okay. 

    "IN" side facing the master is idle in this case. 

    There is no static voltage offset in the TCA9511A that prevents certain series connections like in TCA9517A - of which this device does not allow more than two B-sides to be connected together. 

    While TCA9511A does allow multiple OUT sides to be connected together, it does have an offset voltage to be mindful of. This is described in the VOS spec in the electrical characteristics of the datasheet. VOS can be a maximum of 100mV across PVT. 

    VOS is the offset voltage. Let's say your VOL on "IN" of master 4 is VOL = 100mV, the output voltage on the "OUT" side of the TCA9511A can be upwards of 200mV (due to offset vos(max)). This output voltage this is fed back through the TCA9511A of master3 of which an additional offset voltage is added. The original 100 mV VOL at master4 looks like 300mV at master3. 

    So in short, yes, the TCA9511A buffers can be connected as such. The multi-master arbitration is handled by master1-4, so TCA9511A does not need to worry about that. VOL needs to be taken into consideration due to the offset voltage "stacking" from each TCA9511A connected. 

    Regards,

    Tyler

  • +1 in reply to Tyler Townsend
    Prodigy 40 points

    Tyler-
    Thank you for the very detailed explanation.
    I am very grateful to have confirmed that it is possible to connect four in parallel and two in series.
    The false positives caused by VOS were also explained using diagrams, which made it very easy to understand.
    We will respond with due care.

    best regards,

  • +1 in reply to user1640887
    TI__Mastermind 42421 points

    User1640887,

    If there are no more questions regarding this topic, I will close this thread and mark as resolved. Please feel free to reach out for additional question should any arise.

    Thanks,
    Jack