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SPD5118: How host-side pull-up resistor works in Open-Drain/Push-Pull compatible mode?

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Hi Renesas, 

As JEDEC shown, the SPD Hub supports both open-drain mode and push-pull mode for I2C and I3C compatibility. Open-drain mode requires a pull-up resistor on board or on die, while push-pull mode doesn't. Is there already a specific function in the SPD5118 that could control the pull-up resistor on or off? If not, for board design, how could we switch-off external(on board) or internal(on-die) pull-up resistor when host-side convert to I3C (push-pull) mode from I2C(open-drain) mode?

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    Hi There,

    Apologies for the delay.

    For the host side the pull-up resistor is supposed to be designed outside of the chip to support I2C open Drain mode.

    When power up. SPD5118 is working in I2C mode, pull-up resistors are needed.

    In I3C mode, there is also open drain phase, which also requires pull-up resistors, in push-pull phase the existing pull-up resistors will not interfere with the transaction of I3C if it is in the right range of value.

    Best Regards,
    OV_Renesas

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  • 0

    Hi There,

    Apologies for the delay.

    For the host side the pull-up resistor is supposed to be designed outside of the chip to support I2C open Drain mode.

    When power up. SPD5118 is working in I2C mode, pull-up resistors are needed.

    In I3C mode, there is also open drain phase, which also requires pull-up resistors, in push-pull phase the existing pull-up resistors will not interfere with the transaction of I3C if it is in the right range of value.

    Best Regards,
    OV_Renesas

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