Disclosure includes a controller in an integrated circuit and a related switched mode power supply. The switched mode power supply has an input power line and a ground line. An inductive device and a power switch are connected in series between the input power line and the ground line. The controller has a multifunction pin and is configured for controlling the power switch. A resistor connects the multifunction pin to the input power line. During a startup procedure, the controller provides a first conduction path conducting from the multifunction pin to the ground line. During normal operation, the controller disconnects the first conduction path, and makes the multifunction pin an output node of an error amplifier comparing a regulated output with a target value, to generate a PWM signal for controlling the power switch.