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TCA9509: Is this usage correct?

user1881876
Prodigy 230 points
Part Number: TCA9509
Other Parts Discussed in Thread: TCA9517

Hi There,

I plan to use the TCA9509.

Please let me know if there are any mistakes in usage.


TCA9509_Confirmation matter.pdf

  • +1
    TI__Mastermind 47748 points

    Hi User1881876,

    The TCA9509 is being used incorrectly! A-sides are tied together which cannot happen for this device due to internal current source on the A-side. In an application where the customer needs the contention side to be on the B-side, consider switching to the TCA9517 which implements a static voltage on the B-side.

    One of the main reasons A-sides cannot be tied together is because of the internal current source, which is used to tell the buffer when side is driving a low-logic signal in order to prevent lockup on the I2C bus. 

    Another reason is that the output low voltage produced by the buffer on the A-side when a valid low logic level exists on the b-side input is not low enough to reach the input low contention voltage on the A-side. VOLA (typ) = 0.18V while VILC(typ) = 150 mV. 

    Regards,

    Tyler