JAJSI49C October 2019 – November 2020 LMR33640
PRODUCTION DATA
In some cases, a feedforward capacitor can be used across RFBT to improve the load transient response or improve the loop-phase margin. This is especially true when values of RFBT > 100 kΩ are used. Large values of RFBT in combination with the parasitic capacitance at the FB pin, can create a small signal pole that interferes with the loop stability. A CFF can help mitigate this effect. Use Equation 9 to estimate the value of CFF. The value found with Equation 9 is a starting point. Use lower values to determine if any advantage is gained by the use of a CFF capacitor. The Optimizing Transient Response of Internally Compensated DC-DC Converters with Feed-forward Capacitor Application Report is helpful when experimenting with a feedforward capacitor.