介紹

　　升壓轉換器在便攜式設備中經常使用產生較低的輸出電壓電池輸入電壓。常見的電池配置包括兩到三個堿性或鎳氫電池或，越來越多，Li Ion電池，產生典型的輸入1.8V電壓4.8v之間。

　　The 12Voutput converter showninFigure 1 isdesigned torunfromanytypicalsmallbatterypowersource. This design centers around the LTC?3122 boost converter， which can efficiently generate a regulated output up to 15V from a 1.8V to 5.5V input. The LTC3122 includes a 2.5A internal switch current limit and a full complement of features to handle demanding boost applications， including switching frequency programming， undervoltage lockout， BurstMode? operation or continuousswitchingmode， andtrueoutputdisconnect. The integrated synchronous rectifieris turned offwhen theinductorcurrentapproacheszero， preventingreverse inductorcurrentandminimizingpowerlossatlightloads.

　　This unique output disconnect feature is especially important in applications that have long periods of idle time. While idling， the part can be shut down， leaving the output capacitor fully charged and standing by for quick turn-on. In shutdown， the part draws less than 1μA from the input source.

　　Because the batteries used in portable devices are usually as small as possible， they present high internal impedance under heavy loads， especially close to the end of their discharge cycle. Unlike other boost converters that struggle with high source impedance at startup， the LTC3122 prevents high surge currents at startup.