The primary concern for power management in portable equipment is to prolong battery life by eliminating unnecessary energy consumption. The dual-output power supply of Figure 1 supports this objective while maintaining regulated 5V and 3.3V outputs for as long as the battery or AC-wallcube voltage (or both) are present. Figure 1. These two ICs switch input sources automatically to maintain 5V and 3.3V outputs. The circuit draws battery power only when the AC source is not present. Changeover between battery and wallcube requires no user intervention, and the circuit interposes no extra diodes or MOSFETs in the battery path. Its switchmode regulators deliver as much as 600mA at 5V, and its linear regulator delivers as much as 200mA at 3.3V. IC1, which contains a switchmode regulator and a linear regulator, has separate internal ON/OFF controls that enable its linear regulator to remain on (powered by IC2's output) when its switching regulator is off. IC2 is a switchmode DC-DC converter that boosts the unregulated wallcube output (2V to 5V) to a regulated output of 5.1V. IC1's POUT terminal, capable of delivering 300mA at 95% efficiency (and more at slightly reduced efficiency), is set for a regulated output of 5V. Thus, when the wallcube provides a voltage to IC2, IC2 produces a 5.1V output voltage, which causes IC1 to stop switching; in this situation, the voltage fed back to IC1 exceeds the level where IC1 is permitted to switch. IC1 goes into idle mode, drawing less than 1µA of quiescent current, until the voltage provided by IC2 drops, allowing IC1 to resume switching. This drop of IC2's output is usually caused when the wallcube is unplugged; when this happens, a comparator in IC1 (LBN/LBO) tells IC2 to shut down. This shutdown prevents a flow of reverse current from IC1's output into IC2's OUT pin. This circuit can be updated by substituting the MAX1524 and its accompanying external components for the IC2 switching regulator originally used. The MAX1524 comes in a smaller package than the original MAX608 and doesn't require a current-sense resistor. 相关型号   APP 947: Jan 31, 2002 MAX1524 简单的SOT23封装boost控制器 完整的数据资料 (PDF, 200kB) MAX1705 1至3节电池、大电流、低噪声、升压型DC-DC转换器，带有线性稳压器 完整的数据资料 (PDF, 268kB) 免费样品 MAX608 5V或可调、低电压、升压型DC-DC控制器 完整的数据资料 (PDF, 152kB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (37kB)  AN947, AN 947, APP947, Appnote947, Appnote 947