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TCA9617A: B-side to B-side connection issue

Hemant Khandelwal
Prodigy 10 points
Part Number: TCA9617A
Other Parts Discussed in Thread: TCA9416, TCA9803

Hello TI Team,

I need support. We are using TCA9617ADGKR buffer chip in our project and we not able to communicate in bellow configuration.

In above Image Red line shows communication not happened because understand from bellow link, this IC not support B side to B side communication.

https://www.ti.com/lit/an/scpa054/scpa054.pdf

Can anyone please suggest alternate solution for my requirement, we can modify Host and Device Board but we can’t modify Master/Slave Board.

Requirement is SMBus (I2C) Communication at Fast+ Mode (1MHz) want to use buffer at 3.3V both side.

Regards,

Hemant

  • 0
    TI__Guru 73971 points

    Hemant,

    Just to verify the master/slave unit needs to communicate through the host and device boards into the other master/slave unit, correct? 

    Unfortunately I don't see a way to resolve this current topology. TCA9617 is our only 1MHz I2C buffer and none of the buffers (even the 400kHz ones) would be able to resolve this kind of B-B (offset to offset) connection you have. The fix would need to come from modifying the master/slave units that you have and not the host/device boards. 

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 10 points

    Hello Bobby,

    Thanks for your valuable response, As you mentioned we need to modify Master/Slave unit so can you please suggest how we can resolve by modifying actually Master/Slave unit TPA9617 used 1.2V at FPGA side and 3.3V used at connector side.

    Also can we solve this issue using TCA9416 or TCA9803 ? and how is this if we use this in Host and device board only ?

  • 0 in reply to Hemant Khandelwal
    Guru 317370 points

    The TCA9416 is a passive switch. You can use it if you do not need buffering, but it will not remove the problem (connecting two B sides, even through the TCA9416, is still not allowed).

    The TCA9803 use a current source instead of a static voltage offset, but it still does not allow connecting B sides together.

    You need to exchange the A and B sides on the Master/Slave units, and also on the Host/Device boards. (A/B or A/A can be connected together.) It does not really matter whether you are using the TCA9617 or TCA980x, but the latter outputs lower voltages on its B side.

  • 0 in reply to Hemant Khandelwal
    TI__Mastermind 48308 points

    Hi Hermant,

    I agree with Clemens and Bobby about the current connection. The problem exists with doubling up on static voltage offsets by connecting two b-sides together. 

    Is it possible to change the connections to AB-AB-AB-AB. Or flip the master unit, BA-AB-AB-AB. 

    Regards,

    Tyler