Part Number:BOOSTXL-SENSORS
Hi,
I have a question regarding how to choose the pull-up resistors for SCL / SDA lines. The values chosen in TI BoosterPacks / Reference designs often do not match the value that I calculate from the data sheets and I am wondering what it the reason for this difference. I used 
to determine the upper and lower limits for these resistors.
According to the Bosch BMI160 data sheet (table 26) Rtyp for the SCL / SDA inputs is 100 kΩ. TI uses a for its BOOSTXL-SENSORS (containing a BMI160; software-dl.ti.com/.../index_FDS.html) a combination of 2.2 kOhm to 3.3V and 33 Ohm in the signal lines (which is not even within the 75 to 150 kΩ range set in the data sheet).
For the BQ27421 and the BQ27441, I calculated 5.4 kΩ as lower and 70.8kΩ (based upon Cb = 5 pF; VOL(max) = 0.6V; IOL = 0.5 mA from the data sheet). In contrast, in TIDA-00669 (using the BQ27421) 1 kΩ are used as pull-up to 3.3V, and in BOOSTXL-BATPAKMKII (using the BQ27441) 5.1 kΩ are used to 3.3V, and 200 Ω in the SCL/SDA lines.
Are these differences due to the fact that TI combines several sensors on the board or what else is the reason for the difference? Generally, how do you determine these pull-up resistors if you have several components on the board that use I2C.
Thanks a lot for your help and best regards,
Sebastian