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計(ji)師(shi)(shi)能夠得到的最(zui)理(li)想器件，它可(ke)以(yi)幫助(zhu)設計(ji)師(shi)(shi)節省設計(ji)和PCB布板時(shi)間，也有助(zhu)于(yu)將產品快(kuai)速推向(xiang)市場(chang)。
AnalogicTech可提供專為便攜式和手持式電池供電應用設計的(de)大(da)量電源轉(zhuan)換解決方案。一個成功設計的(de)最重要(yao)特(te)征之一是，器件與目標(biao)應用之間(jian)的(de)匹配是非常完美的(de)。
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主要目標上，而不是電池(chi)充電器(qi)設(she)計(ji)的非常深入(ru)的細節上。
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(she)計用于從一(yi)個DC電(dian)(dian)源或USB口(kou)進(jin)行充電(dian)(dian)，輸入電(dian)(dian)壓可高達7.5V。它只需要一(yi)個外部元件就能實現全部的功能。AAT3681A可精確地(di)為4.2V(或4.375V)鋰離(li)子/聚合物電(dian)(dian)池(chi)組調節電(dian)(dian)池(chi)充電(dian)(dian)電(dian)(dian)壓和(he)電(dian)(dian)流(liu)。
當從AC適配器或USB口充電時，高達300mA的(de)電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流可通過(guo)一個外部電(dian)(dian)(dian)(dian)阻進行設(she)置。電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)狀態(tai)被不間(jian)斷(duan)地監測，一旦錯誤情況(如過(guo)壓、短路或(huo)過(guo)熱)發生，該器件將自(zi)動關斷(duan)，從而保護充(chong)(chong)電(dian)(dian)(dian)(dian)設(she)備(bei)、控制系統(tong)和處(chu)于充(chong)(chong)電(dian)(dian)(dian)(dian)狀態(tai)的(de)電(dian)(dian)(dian)(dian)池。AAT3681A提供一個狀態(tai)監測輸出腳(jiao)，它通過(guo)直接驅(qu)動一個外部LED來指示電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)狀態(tai)。
AAT3681A采用節省空間(jian)的(de)8腳無鉛耐熱(re)SC70JW封(feng)裝，占板(ban)面積只有2.0×2.1mm，工(gong)作溫度范圍為-40℃到+85℃。
最(zui)近發布的(de)AAT3681A是一個單(dan)節電(dian)池充電(dian)器，它(ta)適(shi)合很多(duo)的(de)應用，包括：1)藍(lan)牙耳(er)(er)機(ji)；2)DECT耳(er)(er)機(ji)；3)數碼相機(ji)；4)MP3便攜式(shi)音樂播放機(ji)、PMP；5)腕(wan)表；6)其它(ta)鋰離子/聚合物電(dian)池供電(dian)設備。
盡管該器(qi)件的(de)(de)(de)設計目的(de)(de)(de)是為了(le)讓充(chong)(chong)(chong)電(dian)器(qi)的(de)(de)(de)設計變得(de)非常快速、簡(jian)單和容(rong)易(yi)，但它集成了(le)很多特性來(lai)幫助優化電(dian)池(chi)充(chong)(chong)(chong)電(dian)性能和PCB布板(ban)面(mian)積。下面(mian)是這(zhe)些特性和功能的(de)(de)(de)一部(bu)分(fen)：1)USB或AC適配器(qi)系統電(dian)池(chi)充(chong)(chong)(chong)電(dian)器(qi)；2)15mA到300mA的(de)(de)(de)可編程充(chong)(chong)(chong)電(dian)電(dian)流(liu)(liu)；3)4.0V到7.5V的(de)(de)(de)輸入電(dian)壓范圍；4)與內(nei)部(bu)充(chong)(chong)(chong)電(dian)器(qi)件的(de)(de)(de)高度(du)集成；5)反(fan)向阻(zu)塞(sai)二極(ji)管；6)自動(dong)電(dian)流(liu)(liu)感應；7)自動(dong)再充(chong)(chong)(chong)定(ding)序；8)充(chong)(chong)(chong)滿電(dian)自動(dong)關斷/睡眠模(mo)式(shi)/充(chong)(chong)(chong)電(dian)終(zhong)結；9)關機電(dian)流(liu)(liu)小于1uA；10)電(dian)池(chi)預(yu)充(chong)(chong)(chong)、過(guo)壓和緊急過(guo)熱保護(hu)狀態(tai)下的(de)(de)(de)自動(dong)涓流(liu)(liu)充(chong)(chong)(chong)電(dian)；11)上電(dian)復(fu)位和軟啟動(dong)；12)LED狀態(tai)引腳(jiao)；13)8腳(jiao)2.0×2.1mm SC70JW封(feng)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(tu)1：(a) 典型應用(yong)框(kuang)(kuang)圖(tu)；(b) 功能框(kuang)(kuang)圖(tu)和引腳排列。
該器件的額(e)定工作(zuo)溫度范圍為(wei)-40℃到+85℃。在某一給定的恒流充(chong)電水平(ping)下，當工作(zuo)環境(jing)溫度超出(chu)了該器件封裝的功耗能力時，其充(chong)電控制將進入熱(re)限制狀態。
該器(qi)件(jian)(jian)提(ti)供一個狀(zhuang)(zhuang)態監測(ce)輸出引腳，它可直接驅動一個外部LED來指示(shi)電池充電狀(zhuang)(zhuang)態。器(qi)件(jian)(jian)結溫(wen)和(he)充電狀(zhuang)(zhuang)態被充分監測(ce)，以防錯(cuo)誤狀(zhuang)(zhuang)況(kuang)發生。
AAT3681A實(shi)現了一個完整的(de)保護系統(tong)。在過壓或過溫錯誤狀態發(fa)生時(shi)，該器件將(jiang)自動關斷，以(yi)保護充電(dian)設備(bei)、控制系統(tong)和(he)充電(dian)狀態下的(de)電(dian)池。
充電操作
AAT3681A具有針(zhen)對整個電(dian)(dian)池充(chong)(chong)電(dian)(dian)周(zhou)期的四(si)種基(ji)本(ben)充(chong)(chong)電(dian)(dian)模式：預充(chong)(chong)/涓流(liu)充(chong)(chong)電(dian)(dian)、恒流(liu)/快(kuai)速充(chong)(chong)電(dian)(dian)、恒壓充(chong)(chong)電(dian)(dian)和充(chong)(chong)電(dian)(dian)終(zhong)結。
電池預充
在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)開始(shi)前，為了(le)確保一個安全的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)環境，AAT3681A會檢(jian)查幾個條(tiao)件。輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)必須超過(guo)最小工作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)或(huo)欠(qian)壓(ya)鎖定(ding)閾(yu)值，才能(neng)啟動(dong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)順序。當(dang)這(zhe)些條(tiao)件都已得(de)到(dao)滿足且電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池連接到(dao)BAT引腳(jiao)，AAT3681A就(jiu)檢(jian)查電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)狀態。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低于預(yu)(yu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)閾(yu)值，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)控制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)就(jiu)開始(shi)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池進行預(yu)(yu)充(chong)(chong)(chong)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池預(yu)(yu)充(chong)(chong)(chong)涓流充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流是快速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)恒(heng)流的(de)十分(fen)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
在恒流快速充電(dian)(dian)階段，當電(dian)(dian)池電(dian)(dian)壓(ya)(ya)到達(da)輸(shu)出(chu)(chu)充電(dian)(dian)調(diao)節(jie)閾值時(shi)，系統就進(jin)入恒壓(ya)(ya)充電(dian)(dian)模(mo)式(shi)。調(diao)節(jie)電(dian)(dian)壓(ya)(ya)水平在出(chu)(chu)廠時(shi)設置為(wei)4.2V(±0.5%)。恒壓(ya)(ya)模(mo)式(shi)下(xia)的充電(dian)(dian)電(dian)(dian)流掉下(xia)來，因(yin)為(wei)充電(dian)(dian)中的電(dian)(dian)池單(dan)元快到達(da)其最(zui)大(da)容(rong)量(liang)。
充電周(zhou)期終(zhong)結和再充電順序
在(zai)恒(heng)壓模式下，當(dang)充(chong)電(dian)(dian)電(dian)(dian)流掉到(dao)快速(su)充(chong)電(dian)(dian)電(dian)(dian)流的10%時，該(gai)器件就終(zhong)止充(chong)電(dian)(dian)，并進入睡眠狀(zhuang)態(tai)。充(chong)電(dian)(dian)器將保(bao)持睡眠狀(zhuang)態(tai)，直(zhi)到(dao)電(dian)(dian)池電(dian)(dian)壓降到(dao)電(dian)(dian)池再充(chong)電(dian)(dian)壓閾值以下。
由于(yu)在(zai)睡眠狀(zhuang)態(tai)下消耗(hao)非常低(di)的電(dian)(dian)流，因(yin)此AAT3681A在(zai)不充電(dian)(dian)時可(ke)將電(dian)(dian)池(chi)泄露降(jiang)到最低(di)。這(zhe)(zhe)一(yi)特(te)性對(dui)這(zhe)(zhe)樣一(yi)些應用來說特(te)別有用，其輸(shu)入電(dian)(dian)源(yuan)水(shui)平(ping)可(ke)能(neng)低(di)于(yu)充電(dian)(dian)電(dian)(dian)池(chi)水(shui)平(ping)或欠壓(ya)鎖定水(shui)平(ping)。在(zai)這(zhe)(zhe)些情況下，當AAT3681A輸(shu)入電(dian)(dian)壓(ya)下降(jiang)時，該器件將進(jin)入睡眠狀(zhuang)態(tai)，一(yi)旦輸(shu)入電(dian)(dian)源(yuan)從錯(cuo)誤狀(zhuang)態(tai)下恢(hui)復過來，它再自動(dong)恢(hui)復充電(dian)(dian)。
散熱考慮
AAT3681A采用SC70JW-8封裝(zhuang)，它(ta)能夠散發高(gao)達687mW的功率，當它(ta)被正(zheng)確地(di)安裝(zhuang)在PCB板上時，并具有(you)最大(da)160℃/W的熱阻。在設計(ji)PCB和安排該充電器IC與某一特定應(ying)用設計(ji)中的其它(ta)散熱器件(jian)的位置時，有(you)許多因素(su)應(ying)當加以考慮。
該充電器IC的(de)環境溫(wen)度(du)也將對電池充(chong)電應用的(de)熱限(xian)制有影響。在(zai)某一特(te)定(ding)環境條件下(xia)，可(ke)(ke)以(yi)期望的(de)最大限(xian)制可(ke)(ke)通(tong)過以(yi)下(xia)討論(lun)估計出來。
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) = 最大功耗(hao)(W)
θJA = 封裝熱阻(℃/W)
TJ(MAX) = 最(zui)大器(qi)件結溫(℃) [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(gong)耗
VIN = 輸(shu)入電壓(ya)
VBAT = BAT引(yin)腳上的電池電壓
ICH = 針對某應用編程(cheng)的恒定(ding)充電電流(liu)
IOP = 在(zai)正常工作狀(zhuang)態(tai)下充電器IC消耗的靜態(tai)電流[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(zong)之，最壞的情(qing)況是充(chong)電器IC上(shang)的最大(da)電壓(ya)降，此時，電池電壓(ya)被充(chong)電到(dao)預充(chong)電壓(ya)閾值。
保護(hu)電路；過(guo)壓保護(hu)
一個(ge)(ge)過壓(ya)(ya)(ya)事件(jian)的定(ding)義(yi)為：BAT引腳上(shang)的電(dian)(dian)(dian)壓(ya)(ya)(ya)超過最大電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)(ya)，并被設(she)定(ding)在過壓(ya)(ya)(ya)保(bao)護(hu)閾(yu)值。如果一個(ge)(ge)過壓(ya)(ya)(ya)事件(jian)發(fa)生，AAT3681A充(chong)電(dian)(dian)(dian)控(kong)制電(dian)(dian)(dian)路(lu)將關斷該器件(jian)，直(zhi)到(dao)BAT引腳上(shang)的電(dian)(dian)(dian)壓(ya)(ya)(ya)掉到(dao)OVP電(dian)(dian)(dian)壓(ya)(ya)(ya)水平(ping)以下。AAT3681A在過壓(ya)(ya)(ya)狀態消(xiao)除后(hou)，再恢(hui)復正常的充(chong)電(dian)(dian)(dian)操作。
保護(hu)電路；過(guo)熱(re)關斷(duan)
AAT3681A有(you)一個(ge)熱(re)保護(hu)控制(zhi)電(dian)路，一旦內部裸片溫(wen)度超過預置(zhi)的(de)熱(re)限制(zhi)閾值，它就關(guan)斷充(chong)電(dian)功(gong)能。一旦內部裸片溫(wen)度掉到熱(re)限制(zhi)以下，就自動恢復到以前的(de)正常充(chong)電(dian)狀態。
充電電流的可編程性
用(yong)戶可借助一個(ge)放在ISET引(yin)腳與地之間的(de)(de)設(she)置(zhi)電阻(zu)編程設(she)定恒(heng)流(liu)充(chong)(chong)電水平。快(kuai)速充(chong)(chong)電精度和預充(chong)(chong)涓(juan)流(liu)充(chong)(chong)電電流(liu)，由使用(yong)的(de)(de)設(she)置(zhi)電阻(zu)的(de)(de)容(rong)差(cha)決定。因(yin)此，推薦采用(yong)1%容(rong)差(cha)的(de)(de)金屬(shu)薄(bo)膜電阻(zu)。快(kuai)速充(chong)(chong)電恒(heng)流(liu)電流(liu)范圍從15mA到300mA。
AAT3681A可(ke)以(yi)即(ji)(ji)插即(ji)(ji)用(yong)方式提(ti)供電池(chi)充電器全部(bu)功能。它只(zhi)需要一個外部(bu)元件就可(ke)以(yi)進行全部(bu)操作。該(gai)器件可(ke)提(ti)供極出的性價比(bi)。2mm×2.1mm的小占板面積可(ke)節省(sheng)PCB空間。該(gai)器件適(shi)合各種不同應(ying)用(yong)，從藍牙耳機、MP3播放器到(dao)腕表。AAT3681A是AnalogicTech公司不同復雜度和類(lei)別產品大(da)家庭的最(zui)新成(cheng)員。