An input capacitor, CIN, is required to provide a local bypass for the input voltage source. A low equivalent series resistance (ESR) X5R or X7R ceramic capacitor is best for input voltage filtering and minimizing interference with other circuits. For most applications, a 10-µF ceramic capacitor is recommended from V_IN to ground (system ground, not –V_OUT). The CIN capacitor value can be increased without any limit for better input voltage filtering.

For the inverting buck-boost configuration of the TPS82130, TI does not recommend to install a capacitor from V_IN to –V_OUT. Such a capacitor, if installed, provides an AC path from V_IN to –V_OUT. When V_IN is applied to the circuit, this dV/dt across a capacitor from V_IN to –V_OUT creates a current that must return to ground (the return of the input supply) to complete its loop. This current may flow through the body diode of the internal low-side MOSFET and the inductor to return to ground. Flowing through the body diode pulls the VOUT pin below IC ground, which violates its absolute maximum rating. Such a condition may damage the TPS82130 and is not recommended; therefore, a capacitor from V_IN to –V_OUT is not required or recommended. If such a capacitor (CBP) is present, then a Schottky diode must be installed on the output, as the schematic in Figure 1-8 shows.

Figure 1-8 Installation of Schottky Diode D1 Required, if Installing CBP