JAJU299A June 2017 – January 2023
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 VIN to ground (system ground, not –VOUT). 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 installing a capacitor from VIN to –VOUT. Such a capacitor, if installed, provides an AC path from VIN to –VOUT. When VIN is applied to the circuit, this dV/dt across a capacitor from VIN to –VOUT 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 VIN to –VOUT 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 2-9 shows.