2. AP2161SG-13 Substitution Conclusion The AP2161SG-13 presents several key technical differences from the original TPS2021DRG4, making direct substitution unsuitable. First, it utilizes a P-Channel output stage instead of an N-Channel type, requiring the drive logic to change from active-low to active-high. This fundamental difference can lead to circuit incompatibility. Second, while its rated output current is higher (1A vs. 600mA), its on-resistance is significantly larger (95mOhm vs. 33mOhm), resulting in higher conduction losses and reduced efficiency under equivalent load conditions. Furthermore, the AP2161SG-13 is optimized for USB power switching and includes reverse current protection, whereas the original part is a general-purpose switch. Consequently, the AP2161SG-13 cannot directly replace the TPS2021DRG4. Substitution would require a redesign of the drive circuitry and a thorough re-evaluation of current and power dissipation requirements; otherwise, performance mismatch or functional failure is likely.