ZHCS034C January 2011 – August 2018 TCA4311A
PRODUCTION DATA.
The system pull-up resistors must be strong enough to provide a positive slew rate of 1.25 V/μs on the SDA and SCL pins, in order to activate the boost pull-up currents during rising edges. Choose maximum resistor value R using the formula:
where R is the pull-up resistor value in ohms, VCC(MIN) is the minimum VCC voltage and C is the equivalent bus capacitance in picofarads (pF).
In addition, regardless of the bus capacitance, always choose R ≤ 16 kΩ for VCC = 5.5 V maximum, R ≤ 24 kΩ for VCC = 3.6 V maximum. The start-up circuitry requires logic high voltages on SDAOUT and SCLOUT to connect the backplane to the card, and these pull-up values are needed to overcome the pre-charge voltage.