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TCA9617A: TCA9617 pin status

Bell Ye
Intellectual 1135 points
Part Number: TCA9617A

Hi,

Could you help check the SDAA/SCLA pin status with below condition?

  • EN is low.
  • VCCA (3.3V_stdby) is present
  • VCCB (3.3V) is NOT presen

Many thanks!

Bell

  • 0
    TI__Guru 56270 points

    Hello Bell,

    You have pull up resistors R2061 and R2062 on the SCLA and SDAA, the voltages therefore should be 3.3V assuming R166 and R167 are not populated. If they are and are connected to something else, it will depend on what it's connected to.

    Are you seeing something you aren't expecting on those lines? If so, could you please post oscope shots of SDAA and SCLA. Please also look at VCCA and VCCB to ensure they are the voltages you expect (USE OSCOPE).

    Thanks,
    -Bobby

  • 0 in reply to BOBBY
    TI__Intellectual 1135 points
    Hi Bobby,

    Thanks for response. This circuit is still in design phase, I am not able to probe anything, so we would like you to confirm the SDAA/SCLA status.

    The concern is:
    There are a few I2C programmable power controllers/supervisors on board, and only P3V3_STDBY is present when program them.
    So we need to ensure that when TCA9617 EN is low, VCCB(3.3V) is not present, and only VCCA (P3V3_STDBY) is present, the I2C bus (SDAA/SCLA) needs to be pulled up to VCCA.
    If SDAA/SCLA are internally pull down to ground, then we can’t program the power controllers/supervisors through I2C bus.

    Could you double check the SDAA/SCLA status for this condition?

    thanks,
    Bell
  • 0 in reply to Bell Ye
    TI__Guru 56270 points

    Hey Bell,

    When the EN pin is pulled low, it turns off the drivers which pull the SDAA/SCLA and SDAB/SCLB low or high.

    From the figure above, you can think of it from pin 2 to pin 7 and from pin 3 to pin 6 as an open circuit. So you shouldn't see an issue with the SDA/SCL pins being pulled to ground.

    Thanks,

    -Bobby

  • 0 in reply to Bell Ye
    TI__Mastermind 19475 points

    Hello Bell,

    Please make sure you use the TCA9617B, it has the powered off high impedance on SDA/SCL feature.  The TCA9617A does not and should not be used for new designs.

    -Francis houde

  • 0 in reply to fhoude
    TI__Intellectual 1135 points
    Hi Francis ,

    Got it, thanks for the reply!

    regards,
    Bell