The SSL2109 is a highly integrated switching mode LED controller which enables Constant Current (CC) driving from the mains input. This reference design is a solution for small to medium LED retrofit lamp application, especially for low-power factor design. The reference design is optimized as a buck converter controller suitable for non-isolated, non-dimmable LED retrofit lamps. It can drive long LED strings with, typically 70 V forward voltages. The SSL2109 is intended to operate with higher output voltages, as in modern LED modules. The reference design is designed with a constant output current of 208 mA and can deliver up to 23 W into an LED load with forward voltages between 30 V and 130 V.