1. AP2161SG-13 Substitution Conclusion Conclusion Summary: The AP2161SG-13 can serve as a substitute for the AP2171AS-13, provided the critical difference in control logic polarity is noted and properly addressed. The two parts are nearly identical in their core electrical specifications, protection features, and package dimensions. The primary distinction lies in the input type: the AP2161SG-13 features an "Inverting" input, whereas the AP2171AS-13 is "Non-Inverting." Under the same Enable (EN) signal condition, the switch states of the two ICs are opposite. For example, to power the load, the original device requires a logic-high on the EN pin, while the substitute requires a logic-low. A direct drop-in replacement would result in failure to properly control the power switching. To achieve full compatibility, the preceding control signal's logic level must be adjusted at the design stage—for instance, by inverting the output via MCU firmware or by adding an external inverter circuit.