USB port power switch with integrated fault protection
The TPS2546RTET is a single-channel high-side USB switch from Texas Instruments, rated for 3 A continuous output with a typical on-resistance of 73 mOhm. The 1:1 input-to-output ratio means the switch passes the full input rail to the USB connector when enabled, with the voltage drop determined by the load current times Rds(on). Fault protection is built in: adjustable current limiting, over-temperature shutdown, and undervoltage lockout (UVLO). The current limit threshold is set with an external resistor, letting you tailor the trip point to the USB port's rating without a separate controller. No external Vcc supply is needed — the switch is self-powered from the load rail.
73 mOhm Rds(on) and 3 A current rating — thermal design note
At 3 A, the 73 mOhm typical Rds(on) produces about 657 mW of conduction loss (I²R). A 2-layer board with minimal copper may push junction temperature above 125°C at full load in a 70°C ambient — plan the thermal relief accordingly. For automotive USB ports, look at the TPS2546-Q1 variant if available.