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TCA9617A: Power sequence question

Anders Yang
Prodigy 570 points
Part Number: TCA9617A


1. Could VCCA powered earlier than VCCB?

2. If VCCB and EN are powered, but VCCA kept not powered, will this device works well or have a potential risk?

  • 0
    TI__Guru 62920 points

    Hi Anders,

    Thanks for your questions. We will get back to you on Monday.

    Max

  • 0
    TI__Guru 74851 points

    Hey Anders,

    Anders Yang said:

    Part Number: TCA9617A

    1. Could VCCA powered earlier than VCCB?

    [Bobby] Section 10 of the power supply requirements states this is not allowed. The B version of this device does allow for A side to be larger than B side without any issues occuring.

    2. If VCCB and EN are powered, but VCCA kept not powered, will this device works well or have a potential risk?

    [Bobby] VccB should power up before VccA so in this case, there should be no problem.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 20 points

    Hi, Bobby

    For the question 2, when VCCB and EN are powered, but VCCA is not powered, I want to know if the VCCB side SDAB/SCLB are tied to GND or some undetermin state by VCCA side SDAA/SCLA? Becasue VCCA is not powered.

    Thanks.

  • 0 in reply to rudong shi
    TI__Guru 74851 points

    Hey Rudong,

    "For the question 2, when VCCB and EN are powered, but VCCA is not powered, I want to know if the VCCB side SDAB/SCLB are tied to GND or some undetermin state by VCCA side SDAA/SCLA? Becasue VCCA is not powered."

    No, the device is held in 'reset' mode until VccA powers up so the device will be high impedance until then.

    The only problem A version of this device has is if A side sees power before B side. If B side powers up before A side, the device will work as intended (even if A side has no power).

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 20 points

    Hi, Bobby

    thanks for your feedback.

    one more question, when when VCCB and EN are powered, but VCCA is not powered, both  SDAB/SCLB and SDAA/SCLA are in high impedance state, right?

    or just SDAA/SCLA is in high imedeance state?

    thanks.

  • 0 in reply to rudong shi
    TI__Guru 74851 points

    rudong shi said:

    Hi, Bobby

    thanks for your feedback.

    one more question, when when VCCB and EN are powered, but VCCA is not powered, both  SDAB/SCLB and SDAA/SCLA are in high impedance state, right?

    [Bobby] Correct because in this situation the device is in reset.

    or just SDAA/SCLA is in high imedeance state?

    [Bobby] The TCA9617A is in reset and disabled while VccB and ENable is up but VccA is down.

    thanks.