The ZCD module requires a current-limiting resistor in series with the external voltage source. The impedance and rating of this resistor depends on the external source peak voltage. Select a resistor value that will drop all of the peak voltage when the current through the resistor is less than the maximum input current (ZC02). Refer to the “Electrical Specifications” chapter for more details. Make sure that the ZCD I/O pin internal weak pull-up is disabled so it does not interfere with the current source and sink.
Figure 1. External Resistor
Figure 2. External Voltage Source
