22 mOhm switch in a 3x3 mm footprint
The TPS2556DRBR is a single-channel, high-side power distribution switch from Texas Instruments with a typical on-resistance of 22 mOhm. The switch integrates slew-rate control to limit inrush current during hot-plug events, a status flag output for fault reporting, and protection against overcurrent, overtemperature, and undervoltage lockout.
The 22 mOhm Rds(on) at 5 V input sets the conduction loss floor: at 500 mA the I²R loss is about 5.5 mW, negligible for thermal budget. The real heat comes from the current-limit foldback — if the output is shorted, the part cycles in thermal shutdown, and the exposed-pad thermal resistance (RθJA around 50°C/W with proper board layout) determines how fast it cools. The adjustable current limit (set by a resistor from ILIM to GND) covers a range from roughly 200 mA to 1.5 A, but the 500 mA continuous rating is the safe operating ceiling for the package. For USB 3.0 ports that need 900 mA, this part is under-rated — the TPS2557 (1.5 A version) is the correct choice for that bus power budget. The UVLO threshold at about 2.2 V ensures the switch stays off until the supply rail is stable, which matters for sequencing in multi-rail systems.