Calculation of Pull-up resistor

Thread Starter

Muhammad Salleh

Joined Oct 5, 2018
Hi Guys.

I have a query about the calculation of the pull-up resistor as well as bus capacitance. I was given a PCA9557 chip to assess. I am unsure of how to calculate teh bus capacitance. From the datasheet, it states that
so for the SDA line, the bus capacitance will be 8 + 8(9.5) since i am utilising all 8 io ports.
Additionally, the datasheet states a maximum of 400pf for the bus capacitance. But, from the formula, i calculated that it was wrong.

The SDA line schematic as i have drawn out given to me is as such...

The PCA9557 is connected to 2 other components here and sadly i am unable to find their load capacitance for their datasheet.

Component 1)
Component 2)