The reverse current blocking feature of the TPS22953-Q1 makes it suitable for power multiplexing (MUXing) between two power supplies with different voltages. The SNS and PG pin can be configured to implement break-before-make logic. The circuit in Figure 10-4 shows how the detection of power supply 1 can be used to disable the load switch for power supply 2. By tying the SNS of Load Switch 1 directly to the input, its PG pin is pulled up as soon as the device is enabled.

Figure 10-4 Break-Before-Make Power MUX Schematic

The break-before-make logic ensures that power supply 2 is completely disconnected before power supply 1 is connected. This approach provides very robust reverse current blocking. However, in most cases, this aproach also results in a dip in the output voltage when switching between supplies.

The amount of voltage dip depends on the loading, the output capacitance, and the turn-on delay of the load switch. In this application, leaving the CT pin open results in the shortest turn-on delay and minimizes the output voltage dip.

Table 10-1 summarizes the logic of the PG Signal for Figure 10-4.