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LM5017 Synchronous Buck Converter and COT Slide 16

Fortunately, there is another method to create the required ripple. A network is shown on this slide that creates an artificial ripple that couples into the feedback node. The 46 k resistor and the 3300 pF capacitor create an integrator that generates a ramping voltage every time the switch turns on and goes high which looks quite linear. It ramps up across that 3300 pF capacitor, and then when the switch goes low, it ramps back down. The 0.1 µF capacitor is an AC coupling cap that couples the ramping voltage that was created into the feedback pin. Using this approach does not require a resistor for the ripple on the output voltage, and results in a very low output ripple signal.

PTM Published on: 2012-04-26