SLVAFC5 March 2022 TPS629210 , TPS629210-Q1
An input capacitor, CIN, is required to provide a local bypass for the input voltage source. A low ESR input capacitor is best for input voltage filtering and minimizing interference with other circuits. For most applications, a 10-µF or 22-μF ceramic capacitor is recommended from VIN to ground. The CIN capacitor value can be increased without any limitation for better input voltage filtering.
For the inverting buck – boost configuration of the TPS629210-Q1, it is not recommended to install 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 might flow through the internal low-side MOSFET's body diode and the inductor to return to ground. Flowing through the body diode pulls the SW pin and VOS pin more than 0.3 V below IC ground, violating their absolute maximum rating. Such a condition might damage the TPS629210-Q1 and is not recommended. Therefore, a capacitor from VIN to - VOUT is not needed or recommended. If such a capacitor (C_BYP) is present, then a Schottky diode should be installed on the output per Figure 3-1. Startup testing should be conducted to ensure that the SW and VOS pins are not driven more than 0.3 V below IC ground when VIN is applied.