The pullup resistor value must limit the current through the pass transistor, when it is in the ON state, to about 15 mA. This ensures a pass voltage of 260 mV to 350 mV. If the current through the pass transistor is higher than 15 mA, the pass voltage also is higher in the ON state. To set the current through each pass transistor at 15 mA, the pullup resistor value is calculated as:

Equation 7.

Table 10-2 summarizes resistor values, reference voltages, and currents at 15 mA, 10 mA, and 3 mA. The resistor value shown in the +10% column (or a larger value) must be used to ensure that the pass voltage of the transistor is 350 mV or less. The external driver must be able to sink the total current from the resistors on both sides of the PCA9306-Q1 device at 0.175 V, although the 15 mA applies only to current flowing through the PCA9306-Q1 device.