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TCA9509: A-side for Slave, B-side Master application

Toshiro Imi
Expert 6260 points
Part Number: TCA9509
Other Parts Discussed in Thread: TCA9517

Hello,

Our customer plans TCA9509 A-Side as Slave, 3.3V VCCA, B-side as Master 5V VCCB connecting to HDMI DDC port. Would you give us if this application has potential issue or not.
While he tested TCA9517 B-side for HDMI DDC, 5V, A-side for Slave, 3.3V VCCA, it had an issue of violating DDC capacitance spec. Could you let us know we need to take care about similar issue in case he uses TCA9509 B-side for HDMI DDC port.

best regards,

  • 0
    TI__Mastermind 49400 points

    Hi Toshiro,

    B side of TCA9517 has a static voltage offset which holds the signal low at ~500mV which causes the test equipment to give a much higher capacitance value (false value), this static offset is not on the B side of the TCA9509 so this shouldn't cause a problem if the testing is done on B side of TCA9509. (A side of TCA9509 has the offset).

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 6260 points

    Thank you very much for your suggestion. I understood either A or B side of TCA9509 would be able to be connected to HDMI connector.

    In the datasheet page-1 Simplified Schematic, it looks A-side is connected to Master and B-side is connected to Slave. Is it ok to be connected Slave to A-side and Master to B-side.

    best regards,

  • 0 in reply to Toshiro Imi
    TI__Mastermind 48215 points

    Hi Toshiro,

    This repeater is bidirectional and does not care which side the communication originates on. The simplified schematic is layed out this way because of the placement of the EN pin, which is likely to be controlled by the system leader. The only difference between the I2C pins on the two sides is the static voltage offset as Bobby describes. This also results in different output voltage levels, which may impact which devices can be connected to the A side if they have particularly tight input ranges. You should check the low-level input voltage range of the I2C devices you're using to ensure the low-level output of the repeater is sufficient for them to recognize the signal. If the input thresholds are compatible with the A side output, either side may be used for either device. 

    Regards,
    Eric Schott