Ceramic capacitors with low equivalent series resistance (ESR) are recommended to achieve low output voltage ripple. X5R- or X7R-type dielectrics are recommended for the stable capacitance versus temperature characteristics and DC bias. The higher the DC voltage applied to the capacitor, the less the effective capacitance. A minimum of 2.2-μF capacitance for the input capacitor, CIN, and a 0.1-μF capacitance for a parallel high-frequency input capacitor are required for proper operation.

The CIN from the standard buck evaluation module acts as the bypass capacitor in the inverting buck boost configuration as shown in Figure 1-1.This included capacitor will have an inherent 2.2-μF from the evaluation board, but more bypass capacitance can be added to improve load transient performance.

Evaluating the Bode plot of the circuit under normal operation can also provide insight on the stability of the system. Having a stable phase margin provides the basis for the minimum recommended output capacitance for the inverting buck-boost at different output voltages. Refer to Table 3-1 for the minimum recommended output capacitance.