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Graduate
January 31, 2024
Question

STM32F072V8T6 capacitance and rise time of for I2C

  • January 31, 2024
  • 1 reply
  • 2815 views

I want to know the Bus capacitance and Rise time of STM32F072V8T6 for I2C Calculation, Anyone who has know kindly tell me. Thank you. 

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    1 reply

    Super User
    January 31, 2024

    The capacitance of the bus, as the name suggests,  is defined by the whole bus - not just the microcontroller!

    IO pin capacitance will be in the chip's Datasheet - under electrical characteristics:

    AndrewNeil_0-1706694834923.png

    The following pages give further AC characteristics

    See also:

    AndrewNeil_1-1706695014238.png


    @murali wrote:

     and Rise time . 


    Again, that is defined by the external bus - not the microcontroller.

    Specifically, it is defined by your pull-up resistors.

    See this post: 

    https://electronics.stackexchange.com/questions/1849/is-there-a-correct-resistance-value-for-i2c-pull-up-resistors/473799#473799

    It contains this diagram - which shows you the effect of the pullup value:

     
     

    AndrewNeil_4-1706695333035.png

     

    muraliAuthor
    Graduate
    February 1, 2024

    Thank you

    muraliAuthor
    Graduate
    February 1, 2024

    Hi Andrew Neil,

     

                      Would you inform me of the Hold time of SDA? I want to configure with LT8491 IC of which hole time is at least 300 ns needed.