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Original question:

TPSM846C23EVM-806: Extending the remote sensing points

TPSM846C23: Pull-up resistor for PMBus pins...

fatih cingoz
Intellectual 660 points
Part Number: TPSM846C23
Other Parts Discussed in Thread: TM4C1290NCPDT

Do we need to add pull-up resistor for ALERT pin as we do for other PMBus DATA and CLK pins? If we need what is the optimal pull-up resistor value for PMBus pins (4.7 kOhm ?) Thanks in advance for your response...

  • 0
    TI__Guru 50120 points

    Hi Fatih,

    You can look at the TPSM846C23EVM for a quick reference on the PMBus connections. Notice that only CNTL and PGOOD require a pullup resistor (10kOhm). DATA,CLK, and ALERT go straight to the USB interface. These pins do not require a pullup resistor.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Intellectual 660 points

    Hi Jimmy,

    I took the EVM as reference but I will interface it with TIVA microcontroller. If you take a look tiva TM4C1290NCPDT datasheet page 1256 it says the following:

    " Both SDA and SCL signals must be connected to a positive supply voltage using a pull-up resistor."

    PMBus uses physical layer and electrical layer protocol of I2C which uses two wire as you know as SDA and SCL. If you take a look at application report SLVA704 - June 2015 it also discusses the necessity of the pull-up resistors in I2C Bus.

  • 0 in reply to fatih cingoz
    TI__Guru 50120 points

    Hi Fatih,

    Thank you for the clarification on this and apologizes for I am not too familiar with I2C. After looking at the dongle EVM schematic that is used to converter USB to GPIO, there are indeed pull up resistors for ALERT, DATA and CLK while the TPSM846C23EVM only shows pull up resistors for PGOOD and CNTRL.

    The schematic shows 2.2kOhm for all three lines. I would stick to what the dongle has.

    Regards.

    Jimmy