73 mOhm Rds(on) at 2.5 A — the thermal ceiling
The TPS2540ARTET is a single-channel high-side USB power switch from Texas Instruments, built around an N-channel MOSFET with a typical on-resistance of 73 mOhm. At the 2.5 A maximum output, the conduction loss is I²R = 0.46 W — that heat must be sunk through the 16-WQFN exposed pad to a copper plane. The 73 mOhm figure is the starting point for the thermal budget; actual Rds(on) rises with junction temperature, so derate the current if the board ambient is above 85 °C.
Protection suite: adjustable current limit, OTP, UVLO
Three fault protections are integrated: current limiting that is adjustable via an external resistor, over-temperature shutdown, and under-voltage lockout on the load supply. The adjustable current limit is the key differentiator — it lets the designer set the trip point per USB port (standard downstream port vs charging port) without changing the switch IC. The Status Flag output (open-drain, active low) signals over-current or over-temperature events to the host controller, enabling a controlled port-power-down sequence rather than a hard latch.
For volume BOMs, the active status removes the single-source risk that comes with NRND or EOL parts.