JAJSH54E July 2009 – April 2019 TCA9555
PRODUCTION DATA.
The pull-up resistors, RP, for the SCL and SDA lines need to be selected appropriately and take into consideration the total capacitance of all slaves on the I2C bus. The minimum pull-up resistance is a function of VCC, VOL,(max), and IOL as shown in Equation 5.
The maximum pull-up resistance is a function of the maximum rise time, tr (300 ns for fast-mode operation, fSCL = 400 kHz) and bus capacitance, Cb as shown in Equation 6.
The maximum bus capacitance for an I2C bus must not exceed 400 pF for standard-mode or fast-mode operation. The bus capacitance can be approximated by adding the capacitance of the TCA9555, Ci for SCL or Cio for SDA, the capacitance of wires, connections and traces, and the capacitance of additional slaves on the bus. For further details, see the I2C Pull-up Resistor Calculation application report, SLVA689.