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TCA9517-Q1: can support I2C Multi-master protocol?

Damiano Balzani
Prodigy 200 points
Part Number: TCA9517-Q1
Other Parts Discussed in Thread: TCA9517

Dear all,

i'm designing the bus for an I2C multi-master protocol.

I read on the datasheet that TCA9517-Q1 accomodates the I2C multi-master protocol.

Is it confirmed? if yes, are there any limitations?

Thanks 

Best regards

Damiano

  • 0
    TI__Guru 60540 points

    Hey Damiano,

    The device itself just repeats a signal, it does not know or care how many masters are on the bus or which side the master is on.

    The device does not do arbitration though which is required for a multi-master configuration, this is meant to be supported by the master's software.

    If you require a hardware arbiter then our portfolio does not currently have one.

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 200 points

    Hi Bobby,
    Thanks for your work.

    Your answer resolved my issue

    Thanks

  • 0 in reply to BOBBY
    Prodigy 200 points

    Hi Bobby,

    The datasheet is clearly about bi-directional level shifting but I have a doubt.

    I have to connect two boards which work at 3.3V I2C bus. The communication between them is at 5V I2C bus. 

    I wonder if the following connection diagram is acceptable


    Thanks for your work

    Best regards

    Damiano

  • 0 in reply to Damiano Balzani
    TI__Guru 60540 points

    Hey Damiano,

    Your set up looks like it follows our suggestion in the datasheet where B side of the TCA9517 cannot be connected to each other. A to B is okay.

    One minor thing though, this device was spec'd (electrical characteristics) such that B side ways always greater than A side. So when you have A side larger than B side you may not see the device meeting electrical specs (prop delay values may be double digit nanoseconds longer for example). In terms of functionality though, the device should still work and function as an I2C repeater/buffer.

    If you need to also be within electrical characteristics, let me know as I can give you a few recommendations.

    Also feel free to make an additional post/thread for a schematic check or email me at duynguyen@ti.com if you can't post the schematic online.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 200 points

    Hi Bobby, 
    Thanks for your reply!

    I give you some details.

    My project consists in a 2 boards that share the I2C Bus. The boards are connected by a 40cm long cable. Both buses work a 3.3V but the transmission is at 5V to reduce the noise impact. 

    I thought of TCA9517-Q1 also to increase the bus capacitance 

    The bus is multi-master. The max speed si 400 KHz.

     Also, I need an automotive device

    Can you give me any advice?

    Best regards

    Damiano

  • 0 in reply to Damiano Balzani
    TI__Guru 60540 points

    Just wanted to leave a post incase future searches pop up on this thread to state we took the conversion offline.

    --------

    "I thought of TCA9517-Q1 also to increase the bus capacitance "

    TCA9517 does allow for higher capacitance margin when you use two of them to buffer the cable/transmission line (like what you are doing). The device is spec'd to handle 400pF of capacitance in the datasheet however, outside of the I2C spec (limits at 400pF) this device likely supports higher (not including prop delays).

    -Bobby