Dual-input power path without the diode drop
The TPS2113ADRBR is a 2:1 source selector switch that lets a handheld or mobile device choose between two power inputs — typically a USB port and a battery — without the forward voltage loss of a Schottky OR-ing diode. The internal N-channel FET handles up to 1.25 A continuous, so a 5 V/1 A USB charger or a single-cell Li-ion pack both fit within the current budget. Supply range is 2.8 V to 5.5 V, covering the full discharge curve of a Li-ion cell (3.0 V cut-off) and the 5 V USB bus. The quiescent current is 55 µA — low enough that the selector doesn't eat into the battery standby budget.
Turn-on and turn-off timing margins
The switch has a 1 ms turn-on delay and a 5 ms turn-off delay. That asymmetry means the output stays up during a brief input glitch, but the downstream regulator sees a clean power-up ramp. If your load has a large input capacitor, the 1 ms delay gives the source time to settle before the FET closes.