■ 概要
AS3505K系列是基于CMOS工藝的輸出電流為1A*的低消費電流的同步整流型降壓DC/DC轉(zhuǎn)換器。
該芯片由振蕩器，電壓基準(zhǔn)源，誤差放大器，開關(guān)控制電路，模式控制電路，軟啟動電路，鎖定保護(hù)電路，欠壓鎖定電路(UVLO)，過熱關(guān)斷電路及開關(guān)晶體管等組成。這塊芯片采用開關(guān)器件內(nèi)置的同步整流的方式，加電感和電容即可構(gòu)成一個率的降壓DC/DC轉(zhuǎn)換器.由于封裝為DFN(PLP)2020−8，因此芯片適用于板級高密度貼裝。
AS3505K系列包含，通過內(nèi)建的反饋電阻網(wǎng)絡(luò)以0.1V的步長，&plun;1.5%或18mV的設(shè)置輸出電壓的IC內(nèi)部固定類型(A,B版本)以及可通過外接電阻網(wǎng)絡(luò)決定輸出電壓的可變類型(C版本)。
另外，可以通過MODE引腳選擇不同的工作模式，在輕負(fù)載時能自動切換至率VFM模式的PWM/VFM自動切換模式，和為了減輕噪聲在輕負(fù)載時仍然以固定頻率控制開關(guān)的強制固定在PWM模式的方式。
內(nèi)建的保護(hù)電路包括了，在每個周期內(nèi)限制流過LX電流的電流限流電路和負(fù)載電流過了限流電流或輸出端短路的狀態(tài)持續(xù)時間后關(guān)斷鎖定內(nèi)部驅(qū)動管的鎖定保護(hù)電路。若要釋放鎖定保護(hù)狀態(tài)，把CE使能信號重置，或重置電源電壓（電源電壓低于欠壓鎖定檢測電壓）。電路還內(nèi)建了過熱關(guān)斷保護(hù)電路，如果芯片內(nèi)部的溫度過了值，系統(tǒng)將會重置。
※）輸出電流依賴于工作條件及外部器件，因此這是一個供參考的近似值。
■ 特點
● 消費電流·······················································典型值 40μA(在VFM模式下，無負(fù)載)
● 待機(jī)電流·······················································值 5μA
● 輸入電壓范圍················································2.3V~5.5V(額定值：6.5V)
● 輸出電壓范圍(A,B版本)·································0.6V~3.3V (0.1V步進(jìn)，※0.8V以下的情況，使用條件有限制)
(C版本)····································0.8V～3.3V
● 輸出電壓(A,B版本)·································&plun;1.5%(VOUT≧1.2V)，&plun;18mV(VOUT＜1.2V)
● 反饋電壓(C版本)····································&plun;9mV(VFB=0.6V)
● 輸出電壓/反饋電壓溫度漂移系數(shù)··················&plun;100ppm/°C
● 開關(guān)頻率·······················································典型值 2.25MHz
● 開關(guān)占空比·············································小值 100%
● 內(nèi)置驅(qū)動器導(dǎo)通電阻·····································典型值 P型驅(qū)動管 0.23Ω，N型驅(qū)動管0.20Ω(VIN=3.6V時)
● 欠壓鎖定檢測電壓·········································典型值 2.0V
● 軟起動時間····················································典型值 0.15ms
● 內(nèi)建電感限流電流·········································典型值 1.7A
● 內(nèi)建鎖定保護(hù)電路·········································典型值 1.5ms
● 封裝·······························································DFN(PLP)2020−8
■ 應(yīng)用范圍
● 使用電池供電的設(shè)備
● 照相機(jī)，攝像機(jī)，便攜通訊設(shè)備
● WLAN
