Fortunately, the new LM5017 can be used quite readily to create the bias power, as shown in the application on this slide. The inductor basically becomes a two-winding coupled inductor. Some previous literature has referred to this type of device as a “flybuck”. The LM5017 has an internal linear regulator between the VIN pin and the VCC pin which creates an internal 8 V bias to power up the LM5017 chip. The example shown has a 10 V output that is connected to the VCC pin via the diode, D2. This pushes the VCC pin voltage higher than what the LM5017 is trying to regulate internally, and turns off the linear regulator inside the LM5017. This increases the efficiency and decreases the heat inside the LM5017. As the LM5017 is a constant on-time device, there is a requirement for ripple on the output voltage, specifically on the feedback pin. This is required because there is just a comparator in the controller, and that comparator needs some overdrive. A network is shown in the diagram that creates an artificial ripple that couples into the feedback node. The 46.4 kΩ resistor and the 3300 pF capacitor create an integrator that creates a ramping voltage every time the switch turns on and goes high which looks pretty linear. It ramps up across the 3300 pF capacitor, and then when the switch goes low, it ramps back down. The 0.1 µF cap is an AC coupling cap used to couple the ripple voltage into the feedback pin. The operation of this “flybuck” will be discussed in more detail on the next slide.