This pin is connected to the rectified AC input, and as such requires appropriate separation to other PCB traces to meet the application requirements for functional isolation;
This pin must have 200 kΩ of external resistance to allow the line voltage to be sensed for the X-capacitor discharge block. At least two series resistors should be used to reduce the voltage across the pins of each resistor, with each resistor rated for at least 200 V;
The connection to the resistors that feed the HV pin should have separate dedicated rectifying diodes from the AC input lines, to avoid the DC filtering that the bulk capacitor provides after the main diode bridge; the lower section of the main diode bridge can be shared by the device and the power stage;
A filtering or noise-decoupling capacitor is not recommended, such a capacitor will degrade the X-capacitor sampling ability to distinguish AC from DC input.