STMicroelectronics, L5970D013TR Step-Down Switching Regulator, 1-Channel 1A Adjustable 8-Pin, SO

The L5970D is a step down monolithic power switching regulator capable to deliver up to 1A at output voltages from 1.2V to 35V.
The device uses an internal P-Channel D-MOS transistor (with a typical Rdson of 250mΩ) as switching element to minimize the size of the external components.
An internal oscillator fixes the switching frequency at 250KHz.
Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V bus, available in all computer related applications.
Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.

Switching Voltage Regulators, STMicroelectronics