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TCA9416: Use as only an Accelerator, not a buffer

Benjamin Bawkon
Expert 1085 points
Part Number: TCA9416
Other Parts Discussed in Thread: TCA9803

Tool/software:

Hello TI,

We have been using the AD LTC4311 I2C Bus accelerator very successfully to operate some I2C devices over a fairly long cable.  We are fully aware of the fact that this is an improper use of the I2C bus, but it's worked out very well in this particular application.

We find ourselves needing to re-package this device, and every sq.mm is valuable.  The LTC4311 is rather large, unfortunately, and we have 32 of them in the device (32 I2C Channels).

Could the TCA9416 be used as a replacement by connecting only the "A" side of the device to the bus, and leaving the "B" side floating?  From what I can gather, that should provide acceleration on the A side, just like the LTC4311.

Thank you,
Ben

  • 0
    Expert 1085 points

    Oh, one additional question - which side would be better to use, "A" or "B".  I assume that one side has slight voltage offset to enable bidirection communication, and we would prefer to use the side that has no offset.

  • 0
    Guru 284810 points

    The nearest equivalent of the LTC4311 (current sources) would be the B side of the TCA9803 (the A side can be powered down), but it is only available in the TSSOP package.

    The TCA9416 will work, but it uses a different architecture for the edge accelerators; they trigger when the device detects the beginning of a rising edge (at about 30 % of VCC). A noise bus might generate false triggers.

    When the edge accelerators are not active, the TCA9416 is a passive switch; the A and B sides are identical. The I/O pins on the unused side will not float because of the internal pull-up resistors.

  • 0 in reply to Benjamin Bawkon
    TI__Mastermind 33553 points

    Hi Benjamin,

    Please see Clemens' comments. 

    To answer your question on "A" or "B" side preference, there is no static voltage offset on this device. "A" and "B" side are identical, since technically the TCA9416 is a passive level shifter device with RTA/FTA and internal 10k pull-ups. It does not have buffering between A-side and B-side. 

    Regards,

    Tyler