SCPS207H May 2012 – September 2024 TCA9548A
PRODUCTION DATA
Once all the targets are assigned to the appropriate target channels and bus voltages are identified, the pull-up resistors, Rp, for each of the buses need to be selected appropriately. The minimum pull-up resistance is a function of VDPUX, VOL,(max), and IOL as shown in Equation 1:
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 2:
The maximum bus capacitance for an I2C bus must not exceed 400 pF for fast-mode operation. The bus capacitance can be approximated by adding the capacitance of the TCA9548A, Cio(OFF), the capacitance of wires, connections and traces, and the capacitance of each individual target on a given channel. If multiple channels are activated simultaneously, each of the targets on all channels contribute to total bus capacitance.