Whatever the HV input connection is, a small resistor (RHV)in series with the diodes can limit the current during transientevents. This resistor (of 1 or 2 k for instance, 3 kmaximally), must be low enough. If not, the HV pin voltagemay drop below HVMIN (38 V) during the VCC chargephase because of the voltage drop the start−up currentgenerates across RHV. In such a case, the start−up currentsource may reduce, leading to a longer VCC charge. Also,RHV must be able to dissipate the power produced by thestartup current when the NCP1618 charges up the VCCcapacito