The TS19820CS has built in PWM or linear dimming, DCM mode PFC built in and the ability to drive an external MOSFET. No optocoupler is required in the circuit implementation and the device has ample protection modes built in. Integrating a 3.3 V regulator provides the ability to power a microcontroller or other digital circuitry along with powering the IC itself. This offers the designer reduced parts count and savings on space and cost as well as design and assembly time.