SNVSB97A December 2018 – September 2021 LM34936-Q1
For stable current loop operation and to avoid sub-harmonic oscillations, select the slope capacitor based on Equation 23:
This slope compensation results in “dead-beat” operation, in which the current loop disturbances die out in one switching cycle. Theoretically a current mode loop is stable with half the “dead-beat” slope (twice the calculated slope capacitor value in Equation 23). A smaller slope capacitor results in larger slope signal which is better for noise immunity in the transition region (VIN~VOUT). A larger slope signal, however, restricts the achievable input voltage range for a given output voltage, switching frequency, and inductor. For this design CSLOPE = 220 pF is selected for better transition region behavior while still providing the required VIN range. This selection of slope capacitor, inductor, switching frequency, and inductor satisfies the COMP range limitation explained in Section 7.3.13.