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TCA9509 I2C Level Translator at same Vcc for both busses?

Phil Lizzi
Intellectual 2605 points
Other Parts Discussed in Thread: TCA9509, PCA9515A, TCA9517

Can the TCA9509 be used as an I2C buffer when both busses are powered from the same Vcc supply voltage (e.g. 3.3VDC)?

The datasheet indicates BUS A running at a max. of Vccb - 1.0V ... so I assume some leakage path to Vccb would be established beyond this limit?

What are the cautions in powering both busses from the same Vcc (is there a workaround for this limitation)?

Customer is Tyco Electronics for Cisco design and they need the small size of the TCA9509RVH package (the PCA9515A ... a possible alternative ... is in a 3by3mm pkg which may be too large). Voltage translation not needed ... package size is design priority.

Thanks,

Phil

 

  • 0
    TI__Expert 4745 points

    Phil,

    The TCA9509 datasheet states that Vcca must have a max value of Vccb - 1 V.  However, it has been determined that the TCA9509 can be used with both busses at Vcc.  There is nothing in the design of the TCA9509 that requires the 1V difference between Vcca and Vccb.  A revision will be made in the TCA9509 datasheet to show this specification improvement.

    Best regards,
    Brian Gosselin

  • 0 in reply to Brian Gosselin
    Genius 4830 points

    Hi Brian,

    When will the datasheet be revised?

    Thanks in advance.

  • 0 in reply to toshi-e2e
    TI__Intellectual 2020 points

    The TCA9509 has not been characterized and guaranteed to work over all conditions with VCCA = VCCB. As of now, the datasheet will remain that Vcca have a max value of Vccb - 1 V. Customers will have to use TCA9509 under these conditions at their own discretion.

    If a level-translating repeater with the option to use VCCA = VCCB is required the TCA9517 is a footprint equivalent option that could be used.

    Regards,
    Chris Kraft