The ADP2102 is a synchronous step-down dc-to-dc converter that converts a 2.7 V to 5.5 V unregulated input voltage to a lower regulated output voltage with up to 95% efficiency and 1% accuracy. The low duty cycle capability of the ADP2102 is ideal for USB applications or 5 V systems that power up submicron subvolt processor cores. Its 3 MHz typical operating frequency and excel-lent transient response allow the use of small, low cost 1 μH inductors and 2.2 μF ceramic capacitors. At medium-to-high load currents, it uses a current mode, pseudofixed frequency pulse-width modulation to extend battery life. To ensure the longest battery life in portable applications, the ADP2102 has a power save mode (PSM) that reduces the switching frequency under light load conditions to significantly reduce quiescent current.