SLVAF45 August 2021 TPS51397A , TPS566231 , TPS566235 , TPS566238 , TPS568230
A selection method of feedforward capacitor is proposed in this application report for D-CAP2/D-CAP3 converters based on loop stability analysis. First, the necessity of adding Cff in some application with high output voltage is analyzed. Then the impacts of the Cff on the converter loop is introduced and a method to choose Cff for stability is proposed by ensuring -20dB/decade gain slope at gain crossover frequency. Compared with previous methods, the bode plot test results without Cff aren’t needed to get recommended Cff value, which makes the method more applicable in application design process. Finally, a detailed flow chart is given to help designing application of D-CAP2/D-CAP3 converter. The proposed method is verified by experiments.