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Associate III
January 31, 2024
Question

STM32F072V8T6 capacitance and rise time of for I2C

  • January 31, 2024
  • 6 replies
  • 2862 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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6 replies

Andrew Neil
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

 

A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
muraliAuthor
Associate III
February 1, 2024

Thank you

muraliAuthor
Associate III
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.