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PMIC TPS659037 Unused VPROG and I2C Pins

Michi Yama
Guru 10030 points
Other Parts Discussed in Thread: TPS659037

Hi,

I have one question for TPS659037.

I would like to ask the unused pins handling regarding VPROG, I2C2_SCL_SCE and I2C2_SDA_SDO.

1) VPROG :

According to the Pin Functions in data manual ( slis165a) , it is written in the below.

・Ground or floating @ primary function: OTP programming voltage
・Floating: @ secondary function: TESTV

Also according to 2.9.1 VPROG in the design guide (slia088), it is written in the below.

VPROG is only used for factory testing, and should be left floating.

Which handling is correct, Ground or floating? Our customer connected to the Ground. Is it problem?

If it is problem, please let me know what matter is.

2) I2C2_SCL_SCE, I2C2_SDA_SDO :

According to the Pin Function in the data manual (slis165a), it is written in the below.

・Floating

Also according to 2.6.6 in the design guide(slia088), it is written in the below.

・If I2C2 is unused, both I2C_SCL_SCE and I2C2_SDA_SDO lines should be either pulled up to VIO, or
connected to the I2C1 lines.

Which handling is correct, Floating or pulled up to VIO? Our customer  keeps Floating. Is it problem?

If it is problem, please let me know what matter is.

I appreciate your quick reply.

Best regards,

Michi

  • 0
    TI__Guru**** 393215 points
    Moving this to the PMIC forum.
  • 0
    TI__Genius 16410 points
    Hello Yama-san,

    1) VPROG :

    > Which handling is correct, Ground or floating? Our customer connected to the Ground. Is it problem?
    [Karl] It can be grounded or floating, so it's no issue to connect to ground.

    2) I2C2_SCL_SCE, I2C2_SDA_SDO :

    > Which handling is correct, Floating or pulled up to VIO? Our customer keeps Floating. Is it problem?
    [Karl] It's best practice not to leave input pins floating. However, you shouldn't see any issue if you leave it floating. If you have the opportunity to make the change on a future revision, I would add pull-ups or connect directly to I2C1 clock and data lines.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Guru 10030 points
    Dear Karl-san,

    Thank you for your support.

    My customer has one more question.

    You said " If you have the opportunity to make the change on a future revision, I would add pull-ups or connect directly to I2C1 clock and data lines."

    My customer would like to know why "add pull-ups or connect directly to I2C1 clock and data lines" is better than "floating.
    Please give me more information for this request.

    I appreciate your quick reply.

    Best regards,
    Michi
  • 0 in reply to Michi Yama
    TI__Genius 16410 points
    Hello Michi,

    Since I2C2 pins are inputs without any pull-up resistor internally, it's best practice not to leave the pin floating. There could be some increased current draw, and the node value is undetermined when floating. So it's low risk to see any issue besides some leakage current from VIO, but it's best practice to not leave these pins floating.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Guru 10030 points

    Dear karl-san,

    Thank you for your cooperation.

    I have one question regarding the previous your answer.

    >>2) I2C2_SCL_SCE, I2C2_SDA_SDO :
    >> 
    >> Which handling is correct, Floating or pulled up to VIO? Our customer keeps Floating. Is it problem?
    >[Karl] It's best practice not to leave input pins floating. However, you shouldn't see any issue if you leave it floating. If you have the opportunity to make the change on a future revision, I would add pull-ups or connect directly to I2C1 clock and data lines.

    Customer is thinking how to handle the unused I2C2 pins as the below.

    Pin handling \ PIN name :  I2C2_SCL_SCE         I2C2_SDA_SDO

      idea#1                                    VIO                                VIO

      idea#2                                     VIO                       I2C1_SDA_SDI

      idea#3                               I2C1_SCL_SCK                  VIO

      idea#4                               I2C1_SCL_SCK         I2C1_SDA_SDI

     

    According to your adivc, the above handlings are all OK, I think. Is my understanding correct?

    If there are some handling that you don't recommend, please let me know.

    I appreciate your quick reply.

    Best regards,

    Michi

     

  • 0 in reply to Michi Yama
    TI__Genius 16410 points
    Yama-san,

    Any of those are ok for the PMIC. The only time you would not want to connect them to the I2C1 lines is if the I2C address 0x12 is already used on the bus. But assuming there is no address contention, all of the four ideas are ok.

    Regards,
    Karl