SLVA689 February   2015 DS90UH940N-Q1 , LM8323 , LM8325-1 , LM8327 , LM8328 , LM8330 , LM8333 , LM8335 , P82B715 , P82B96 , PCA9306 , PCA9306-Q1 , PCA9515A , PCA9515B , PCA9518 , PCA9534 , PCA9534A , PCA9535 , PCA9536 , PCA9538 , PCA9539 , PCA9543A , PCA9544A , PCA9545A , PCA9546A , PCA9548A , PCA9554 , PCA9554A , PCA9555 , PCA9557 , PCF8574 , PCF8574A , PCF8575 , PCF8575C , TCA4311A , TCA5405 , TCA6408A , TCA6416A , TCA6418E , TCA6424A , TCA6507 , TCA8418 , TCA8418E , TCA8424 , TCA9406 , TCA9509 , TCA9517 , TCA9517A , TCA9534 , TCA9534A , TCA9535 , TCA9538 , TCA9539 , TCA9539-Q1 , TCA9543A , TCA9544A , TCA9545A , TCA9546A , TCA9548A , TCA9554 , TCA9554A , TCA9555 , TCA9617A , TCA9617B , TCA9800 , TCA9801 , TCA9802 , TCA9803

 

  1. I2CBus Pullup Resistor Calculation
    1.     Trademarks
    2. 1 Introduction
    3. 2 Pullup Resistor Calculation
    4. 3 Speed Versus Power Trade-off
    5. 4 Example

Example

For Fast-mode I2C communication with the following parameters, calculate the pullup resistor value.

Cb = 200 pF, VCC = 3.3 V

Solution:

Taking the values from Table 1:

Equation 7. Eq7_Rp_slva689.gif
Equation 8. Eq8_Rp_slva689.gif

Therefore, we can select any available resistor value between 966.667 Ω and 1.77 kΩ. The value of the pullup resistor can be selected based on the trade-off for the power consumption and speed.