1. AP2161SG-13 Substitution Conclusion The AP2161SG-13 is identical to the AP2171DSG-13 in all key electrical parameters, package, protection features, and load capability, making it technically feasible for direct substitution. The only significant difference lies in the input control logic: the original part (AP2171DSG-13) features a non‑inverting input, where a high‑level signal enables the switch, while the substitute (AP2161SG-13) has an inverting input, requiring a low‑level signal to turn the switch on. If directly replaced, the system control signal logic must be inverted—for instance, by adding an external logic gate or implementing a software inversion—otherwise the power‑switch state will be opposite to the intended condition, leading to circuit malfunction. No other circuit modifications are necessary aside from this logic adjustment.