USB鋰離子/聚合物電池充電器解決方案
AAT3681A的封裝尺寸非常小，只有2.0×2.1mm，這使得它非常適合便攜式和超便攜式應用。這一器件是即插即用型充電器設(she)計師能夠得到的最理想器件，它(ta)可以幫助(zhu)設(she)計師節省(sheng)設(she)計和PCB布板時間，也有(you)助(zhu)于(yu)將產品(pin)快速推向市(shi)場。
AnalogicTech可提供專為便攜式和手持式電池供電應用設計(ji)的大量電源轉(zhuan)換解決方案。一(yi)個(ge)成(cheng)功設計(ji)的最重(zhong)要特征之(zhi)一(yi)是，器件與目標應用之(zhi)間的匹配(pei)是非(fei)常(chang)完美(mei)的。
就AAT3681A來說，現代便攜式應用的功能正在以一個令人瞠目結舌的速度擴展，所有類型的新功能正被添加進去以滿足市場的要求。因此，提供這一器件的目的是把單節鋰離子電池充電器所需的所有功能全部集成在一起，以及最大程度地減小電路設計師的設計工作量。現在他們可以把精力更多地集中在充電器設計的(de)主要目標上，而(er)不(bu)是電池充(chong)電器設計(ji)的(de)非常(chang)深入的(de)細(xi)節(jie)上。
AAT3681A Battery Manager是一個高度集成的單節鋰離子/聚合物電池充電器IC，設計用于(yu)從一(yi)個(ge)DC電(dian)(dian)源或USB口進行(xing)充(chong)電(dian)(dian)，輸入電(dian)(dian)壓可高達7.5V。它只需要一(yi)個(ge)外部(bu)元件就能實現全部(bu)的功能。AAT3681A可精(jing)確地為4.2V(或4.375V)鋰離子/聚(ju)合物電(dian)(dian)池組(zu)調節電(dian)(dian)池充(chong)電(dian)(dian)電(dian)(dian)壓和電(dian)(dian)流(liu)。
當從AC適配器或USB口充電時，高(gao)達300mA的(de)電(dian)池充電(dian)電(dian)流可通過(guo)一(yi)個外部電(dian)阻進行設置。電(dian)池充電(dian)狀態被不間斷地監(jian)測(ce)，一(yi)旦錯誤情況(如過(guo)壓(ya)、短路(lu)或(huo)過(guo)熱)發(fa)生(sheng)，該器件將自(zi)動(dong)(dong)關斷，從而保護(hu)充電(dian)設備、控制(zhi)系統和處于充電(dian)狀態的(de)電(dian)池。AAT3681A提供一(yi)個狀態監(jian)測(ce)輸出腳，它(ta)通過(guo)直(zhi)接驅動(dong)(dong)一(yi)個外部LED來指示電(dian)池充電(dian)狀態。
AAT3681A采用節省空(kong)間(jian)的(de)8腳無(wu)鉛耐熱SC70JW封(feng)裝，占板面積只有2.0×2.1mm，工(gong)作溫(wen)度范(fan)圍(wei)為-40℃到(dao)+85℃。
最近發布的AAT3681A是一個單節電池充電器，它(ta)適合(he)(he)很多的應用，包括(kuo)：1)藍牙耳機(ji)；2)DECT耳機(ji)；3)數碼相機(ji)；4)MP3便攜式(shi)音樂播放機(ji)、PMP；5)腕表；6)其它(ta)鋰離子(zi)/聚合(he)(he)物電池供(gong)電設備(bei)。
盡管(guan)該(gai)器(qi)件(jian)的(de)設計目的(de)是為(wei)了(le)讓充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)的(de)設計變得非(fei)常快(kuai)速(su)、簡單和容易，但(dan)它集成了(le)很(hen)多特(te)性來幫助優化電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)性能和PCB布板(ban)面積。下面是這些特(te)性和功能的(de)一(yi)部分：1)USB或AC適(shi)配器(qi)系統電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)；2)15mA到(dao)300mA的(de)可編程充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)；3)4.0V到(dao)7.5V的(de)輸(shu)入電(dian)(dian)(dian)(dian)壓范(fan)圍；4)與內部充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)件(jian)的(de)高度集成；5)反向阻塞二(er)極管(guan)；6)自動(dong)(dong)(dong)電(dian)(dian)(dian)(dian)流(liu)感(gan)應；7)自動(dong)(dong)(dong)再(zai)充(chong)(chong)定序；8)充(chong)(chong)滿電(dian)(dian)(dian)(dian)自動(dong)(dong)(dong)關斷/睡眠模(mo)式/充(chong)(chong)電(dian)(dian)(dian)(dian)終結；9)關機(ji)電(dian)(dian)(dian)(dian)流(liu)小于1uA；10)電(dian)(dian)(dian)(dian)池預充(chong)(chong)、過(guo)壓和緊急過(guo)熱保護狀(zhuang)態下的(de)自動(dong)(dong)(dong)涓流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)；11)上電(dian)(dian)(dian)(dian)復(fu)位和軟(ruan)啟(qi)動(dong)(dong)(dong)；12)LED狀(zhuang)態引腳(jiao)；13)8腳(jiao)2.0×2.1mm SC70JW封裝。
模塊描述
單節鋰離子/聚合物電池正在變成便攜式和超便攜式應用的主要選擇。針對這一終端市場而開發的AAT3681A是一個高性能的電池充電器，設計用于從一個外部電源以高達300mA的電流對單節鋰離子/聚合物電池進行充電。這一充電電流可使用一個外部電阻在15mA到300mA的很寬范圍內進行定制。這就允許適配器/USB口在不同的應用中執行快速充電。它是一個獨立的充電解決方案，只需要一個外部元件就可以實現全部功能。這一器件可精確地為4.2V鋰離子/聚合物電池組調節電池充電電壓和電流。
圖1：(a) 典(dian)型(xing)應用框(kuang)圖；(b) 功能(neng)框(kuang)圖和引腳排列。
該(gai)器件的額(e)定工(gong)作溫度范圍為-40℃到+85℃。在某一給(gei)定的恒(heng)流充(chong)(chong)電(dian)水(shui)平下(xia)，當工(gong)作環境(jing)溫度超出了該(gai)器件封裝的功耗能力時，其充(chong)(chong)電(dian)控(kong)制將進(jin)入熱限(xian)制狀態(tai)。
該(gai)器件提供一(yi)(yi)個(ge)狀(zhuang)(zhuang)態監(jian)測(ce)輸出引腳，它可直接驅動一(yi)(yi)個(ge)外部LED來指示電池充(chong)電狀(zhuang)(zhuang)態。器件結溫(wen)和充(chong)電狀(zhuang)(zhuang)態被充(chong)分監(jian)測(ce)，以(yi)防錯誤狀(zhuang)(zhuang)況發生。
AAT3681A實現了(le)一個(ge)完整(zheng)的保護(hu)系(xi)統。在過壓(ya)或過溫錯誤狀態發生(sheng)時，該器(qi)件將自動關斷，以保護(hu)充(chong)電(dian)設備、控制系(xi)統和充(chong)電(dian)狀態下(xia)的電(dian)池(chi)。
充電操作
AAT3681A具有針對整(zheng)個(ge)電(dian)(dian)池充(chong)(chong)電(dian)(dian)周期的四(si)種基(ji)本(ben)充(chong)(chong)電(dian)(dian)模(mo)式：預充(chong)(chong)/涓流充(chong)(chong)電(dian)(dian)、恒(heng)流/快(kuai)速充(chong)(chong)電(dian)(dian)、恒(heng)壓(ya)充(chong)(chong)電(dian)(dian)和充(chong)(chong)電(dian)(dian)終結(jie)。
電池預充
在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)開始前(qian)，為了確保一個安(an)全的充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)環境，AAT3681A會檢查幾個條(tiao)件。輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源必須超(chao)過最小(xiao)工作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或欠(qian)壓鎖定閾(yu)值，才能(neng)啟(qi)動充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)順序(xu)。當這些條(tiao)件都(dou)已得到(dao)(dao)滿足且電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)連接到(dao)(dao)BAT引腳，AAT3681A就檢查電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的狀態(tai)。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓低于預(yu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓閾(yu)值，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)控制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)就開始對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)進(jin)行(xing)預(yu)充(chong)(chong)(chong)(chong)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)預(yu)充(chong)(chong)(chong)(chong)涓流充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流是(shi)快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)恒流的十分之一。
例如，如果可編程快速充電電流是300mA，那么預充電流就是30mA。電池單元預充是針對深度放電電池單元的一種安全預防措施，它也有助于限制導通晶體管上的功耗，因為此時該器件上的電壓差是最大的。恒流充電電池單元預充一直持續到BAT引腳上的電壓超出預充電壓閾值。到達此點后，該器件開始恒流充電階段。恒流充電幅值由用戶通過設置電阻進行編程。AAT3681A一直保持恒流充電模式，一直到電池到達電壓調節點。
恒壓充電
在恒(heng)(heng)流快(kuai)速充(chong)電(dian)(dian)階(jie)段，當電(dian)(dian)池(chi)電(dian)(dian)壓到達輸出充(chong)電(dian)(dian)調節閾(yu)值時，系統(tong)就(jiu)進入恒(heng)(heng)壓充(chong)電(dian)(dian)模(mo)(mo)式。調節電(dian)(dian)壓水平(ping)在出廠時設置為4.2V(±0.5%)。恒(heng)(heng)壓模(mo)(mo)式下(xia)的充(chong)電(dian)(dian)電(dian)(dian)流掉(diao)下(xia)來(lai)，因為充(chong)電(dian)(dian)中的電(dian)(dian)池(chi)單元(yuan)快(kuai)到達其最大容(rong)量。
充(chong)(chong)電周期(qi)終結和再充(chong)(chong)電順序(xu)
在恒壓模(mo)式下，當充(chong)(chong)電(dian)電(dian)流掉到快速充(chong)(chong)電(dian)電(dian)流的(de)10%時，該器件就終止充(chong)(chong)電(dian)，并進入(ru)睡(shui)眠(mian)狀態。充(chong)(chong)電(dian)器將(jiang)保(bao)持睡(shui)眠(mian)狀態，直到電(dian)池(chi)電(dian)壓降到電(dian)池(chi)再充(chong)(chong)電(dian)壓閾值以下。
由于(yu)在(zai)(zai)睡眠(mian)狀態(tai)下消耗非(fei)常低的電(dian)流，因此AAT3681A在(zai)(zai)不充(chong)電(dian)時可將電(dian)池泄露降到(dao)最低。這(zhe)一(yi)(yi)特性對這(zhe)樣一(yi)(yi)些(xie)應用來說特別有(you)用，其(qi)輸入電(dian)源水平(ping)(ping)可能低于(yu)充(chong)電(dian)電(dian)池水平(ping)(ping)或欠壓鎖定(ding)水平(ping)(ping)。在(zai)(zai)這(zhe)些(xie)情況下，當(dang)AAT3681A輸入電(dian)壓下降時，該器(qi)件將進入睡眠(mian)狀態(tai)，一(yi)(yi)旦輸入電(dian)源從錯(cuo)誤狀態(tai)下恢復過來，它再自動恢復充(chong)電(dian)。
散熱考慮
AAT3681A采用SC70JW-8封裝，它(ta)能夠散(san)發高(gao)達687mW的功(gong)率(lv)，當它(ta)被正確地安裝在(zai)PCB板上時，并具有最大160℃/W的熱阻(zu)。在(zai)設計(ji)PCB和安排該充電(dian)器IC與(yu)某(mou)一特定應用設計(ji)中的其它(ta)散(san)熱器件的位置時，有許多因素應當加以(yi)考慮。
該充電器IC的環境溫度也將對(dui)電池充(chong)電應用的熱(re)限制(zhi)有影響(xiang)。在某一(yi)特定環境條件下，可以(yi)期望的最大限制(zhi)可通過以(yi)下討(tao)論(lun)估計出(chu)來。
首先，某一特定環境下的最大功耗可通過下式計算出來：
其中：
PD(MAX) = 最大功(gong)耗(W)
θJA = 封(feng)裝熱阻(℃/W)
TJ(MAX) = 最大器件(jian)結溫(℃) [135℃]
TA = 環境溫度(℃)
其次，功耗可通過下式計算出來：
其中：
PD = 器件的總功耗(hao)
VIN = 輸入電壓
VBAT = BAT引腳上的電池電壓
ICH = 針對(dui)某應用(yong)編程的恒定充電電流
IOP = 在正常(chang)工作狀(zhuang)態(tai)(tai)下(xia)充(chong)電(dian)器IC消(xiao)耗的靜態(tai)(tai)電(dian)流[0.5mA]
通過替代，我們可以推導出在到達熱限制條件(熱循環)前的最大充電電流。該最大充電電流是設計電池充電器應用時的關鍵因素。
總之(zhi)，最(zui)壞的(de)情況是充電器IC上(shang)的(de)最(zui)大電壓降，此時，電池(chi)電壓被(bei)充電到(dao)預充電壓閾(yu)值。
保護電路；過壓(ya)保護
一個過(guo)壓(ya)(ya)(ya)事件的(de)定義為：BAT引腳(jiao)(jiao)上(shang)的(de)電(dian)(dian)壓(ya)(ya)(ya)超過(guo)最大電(dian)(dian)池充電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)，并被設定在(zai)過(guo)壓(ya)(ya)(ya)保(bao)護閾值。如果一個過(guo)壓(ya)(ya)(ya)事件發生，AAT3681A充電(dian)(dian)控制(zhi)電(dian)(dian)路將關(guan)斷(duan)該器件，直到BAT引腳(jiao)(jiao)上(shang)的(de)電(dian)(dian)壓(ya)(ya)(ya)掉(diao)到OVP電(dian)(dian)壓(ya)(ya)(ya)水平以下(xia)。AAT3681A在(zai)過(guo)壓(ya)(ya)(ya)狀態(tai)消除后，再恢復正常的(de)充電(dian)(dian)操作。
保護(hu)電(dian)路；過熱關(guan)斷
AAT3681A有一個熱(re)保護(hu)控制(zhi)電(dian)路，一旦內部裸(luo)片溫(wen)度超(chao)過預置(zhi)的(de)熱(re)限制(zhi)閾值，它就關斷充(chong)電(dian)功能。一旦內部裸(luo)片溫(wen)度掉到(dao)熱(re)限制(zhi)以下，就自動恢復到(dao)以前的(de)正常充(chong)電(dian)狀態。
充電電流的可編程性
用戶可(ke)借助一個放在ISET引腳(jiao)與(yu)地之間(jian)的(de)(de)設置(zhi)電(dian)(dian)(dian)阻編程(cheng)設定恒流(liu)充(chong)(chong)電(dian)(dian)(dian)水(shui)平。快速充(chong)(chong)電(dian)(dian)(dian)精度和預充(chong)(chong)涓流(liu)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)，由(you)使用的(de)(de)設置(zhi)電(dian)(dian)(dian)阻的(de)(de)容(rong)差(cha)決定。因此，推薦采用1%容(rong)差(cha)的(de)(de)金屬薄膜電(dian)(dian)(dian)阻。快速充(chong)(chong)電(dian)(dian)(dian)恒流(liu)電(dian)(dian)(dian)流(liu)范(fan)圍從15mA到300mA。
AAT3681A可(ke)以即(ji)插即(ji)用方式(shi)提供電(dian)(dian)池(chi)充電(dian)(dian)器全部(bu)功能。它只需(xu)要(yao)一(yi)個外部(bu)元件就可(ke)以進行(xing)全部(bu)操作(zuo)。該(gai)器件可(ke)提供極出(chu)的性價(jia)比。2mm×2.1mm的小占板面積可(ke)節(jie)省PCB空間。該(gai)器件適合各種不同(tong)應(ying)用，從(cong)藍牙耳(er)機、MP3播放器到(dao)腕表(biao)。AAT3681A是(shi)AnalogicTech公司不同(tong)復雜度和類(lei)別產品大家(jia)庭的最新成(cheng)員(yuan)。