ZHCSX36K July 2001 – September 2024 PCF8574
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 targets on the I2C bus. The minimum pull-up resistance is a function of VCC, VOL,(max), and IOL:
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:
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 PCF8574 device, Ci for SCL or Cio for SDA, the capacitance of wires/connections/traces, and the capacitance of additional targets on the bus.