The ADP2108 is a high efficiency， low quiescent current stepdown dc-to-dc converter manufactured in two different packages. The total solution requires only three tiny external components. It uses a proprietary， high speed current mode， constant frequency PWM control scheme for excellent stability and transient response. To ensure the longest battery life in portable applications， the ADP2108 has a power save mode that reduces the switching frequency under light load conditions. The ADP2108 runs on input voltages of 2.3 V to 5.5 V， which allows for single lithium or lithium polymer cell， multiple alkaline or NiMH cell， PCMCIA， USB， and other standard power sources. The maximum load current of 600 mA is achievable across the input voltage range. The ADP2108 is available in fixed output voltages of 3.3 V， 3.0 V， 2.5 V， 2.3 V， 1.82 V， 1.8 V， 1.5 V， 1.3 V， 1.2 V， 1.1 V， and 1.0 V. All versions include an internal power switch and synchronous rectifier for minimal external part count and high efficiency. The ADP2108 has an internal soft start and is internally compensated. During logic controlled shutdown， the input is disconnected from the output and the ADP2108 draws less than 1 μA from the input source. Other key features include undervoltage lockout to prevent deep battery discharge and soft start to prevent input current overshoot at startup. The ADP2108 is available in 5-ball WLCSP and 5-lead TSOT packages. The ADP2109 provides the same features and operations as the ADP2108 and has the additional function of a discharge switch in the WLCSP package.