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(ji)師(shi)(shi)能(neng)夠得到(dao)的最理想器件，它可(ke)以幫助設(she)計(ji)師(shi)(shi)節省設(she)計(ji)和(he)PCB布板(ban)時間，也有助于將產品(pin)快速推向市場(chang)。
AnalogicTech可提供專為便攜式和手持式電池供電應(ying)用設計的大量電源(yuan)轉換(huan)解決方案。一(yi)個成功設計的最重要特征之(zhi)一(yi)是(shi)，器件與目(mu)標應(ying)用之(zhi)間的匹配(pei)是(shi)非(fei)常完美(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主要目標上，而不是電池(chi)充電器(qi)設計(ji)的非常深入的細(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，設計用于從一(yi)(yi)個DC電(dian)源(yuan)或USB口進(jin)行充(chong)電(dian)，輸入電(dian)壓(ya)可(ke)高達(da)7.5V。它只需要(yao)一(yi)(yi)個外部(bu)元件就能實現(xian)全部(bu)的功(gong)能。AAT3681A可(ke)精確地為(wei)4.2V(或4.375V)鋰(li)離子/聚合物電(dian)池(chi)組調節電(dian)池(chi)充(chong)電(dian)電(dian)壓(ya)和(he)電(dian)流(liu)。
當從AC適配器或USB口充電時，高達300mA的電(dian)池(chi)充(chong)(chong)電(dian)電(dian)流可(ke)通過一(yi)個外部電(dian)阻(zu)進行設置。電(dian)池(chi)充(chong)(chong)電(dian)狀態(tai)被不間斷(duan)地(di)監測(ce)，一(yi)旦錯誤(wu)情(qing)況(如過壓、短路或(huo)過熱(re))發生，該器件將自動(dong)關斷(duan)，從而保護充(chong)(chong)電(dian)設備、控制系統(tong)和處(chu)于充(chong)(chong)電(dian)狀態(tai)的電(dian)池(chi)。AAT3681A提供(gong)一(yi)個狀態(tai)監測(ce)輸出腳，它通過直(zhi)接(jie)驅動(dong)一(yi)個外部LED來指示(shi)電(dian)池(chi)充(chong)(chong)電(dian)狀態(tai)。
AAT3681A采用節省空間(jian)的8腳無鉛耐熱(re)SC70JW封(feng)裝，占板面積只有2.0×2.1mm，工作(zuo)溫度范(fan)圍為(wei)-40℃到+85℃。
最近發(fa)布的AAT3681A是一個單(dan)節電(dian)池(chi)充電(dian)器，它適合很多的應(ying)用，包括：1)藍牙(ya)耳(er)機；2)DECT耳(er)機；3)數碼相機；4)MP3便攜式音樂播放機、PMP；5)腕表；6)其它鋰離子(zi)/聚(ju)合物電(dian)池(chi)供(gong)電(dian)設備。
盡管該器(qi)(qi)件的(de)(de)(de)設(she)計目的(de)(de)(de)是為了讓(rang)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)的(de)(de)(de)設(she)計變(bian)得非常快速、簡(jian)單和(he)容易(yi)，但它集(ji)成了很多特性來(lai)幫助優化電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)性能(neng)(neng)和(he)PCB布板(ban)面積。下(xia)(xia)面是這些(xie)特性和(he)功(gong)能(neng)(neng)的(de)(de)(de)一部(bu)分：1)USB或AC適配器(qi)(qi)系(xi)統電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)；2)15mA到300mA的(de)(de)(de)可編程充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)；3)4.0V到7.5V的(de)(de)(de)輸入電(dian)(dian)(dian)(dian)(dian)(dian)壓范圍；4)與內部(bu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)件的(de)(de)(de)高度集(ji)成；5)反(fan)向阻塞二極管；6)自(zi)(zi)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)感應；7)自(zi)(zi)動(dong)再充(chong)(chong)(chong)定(ding)序；8)充(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)自(zi)(zi)動(dong)關(guan)斷/睡眠模式(shi)/充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終結(jie)；9)關(guan)機電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)小(xiao)于1uA；10)電(dian)(dian)(dian)(dian)(dian)(dian)池預充(chong)(chong)(chong)、過壓和(he)緊急過熱保(bao)護(hu)狀態(tai)下(xia)(xia)的(de)(de)(de)自(zi)(zi)動(dong)涓流(liu)(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)；11)上電(dian)(dian)(dian)(dian)(dian)(dian)復(fu)位和(he)軟啟動(dong)；12)LED狀態(tai)引腳；13)8腳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) 典型應用(yong)框圖；(b) 功(gong)能框圖和引腳排列。
該器件(jian)(jian)的額(e)定工(gong)作溫(wen)度范圍為-40℃到+85℃。在某(mou)一給定的恒流充(chong)電水平下(xia)，當工(gong)作環境溫(wen)度超出了該器件(jian)(jian)封裝(zhuang)的功耗能(neng)力(li)時，其充(chong)電控制將進入熱(re)限制狀態。
該器件提供一(yi)個(ge)狀(zhuang)態(tai)監(jian)測輸出引(yin)腳，它可直接(jie)驅動一(yi)個(ge)外部LED來指示電(dian)池充(chong)電(dian)狀(zhuang)態(tai)。器件結(jie)溫和(he)充(chong)電(dian)狀(zhuang)態(tai)被充(chong)分監(jian)測，以防(fang)錯誤狀(zhuang)況發生。
AAT3681A實現了一個完整的保護系(xi)(xi)統。在過壓或過溫(wen)錯誤狀態發(fa)生時，該(gai)器件將自動關斷，以(yi)保護充(chong)電設備、控制系(xi)(xi)統和充(chong)電狀態下的電池。
充電操作
AAT3681A具有(you)針對整個(ge)電(dian)池(chi)充(chong)(chong)(chong)電(dian)周期的四種(zhong)基本充(chong)(chong)(chong)電(dian)模式：預(yu)充(chong)(chong)(chong)/涓流充(chong)(chong)(chong)電(dian)、恒流/快(kuai)速充(chong)(chong)(chong)電(dian)、恒壓充(chong)(chong)(chong)電(dian)和充(chong)(chong)(chong)電(dian)終結(jie)。
電池預充
在(zai)充(chong)(chong)(chong)電(dian)(dian)開(kai)始前，為(wei)了(le)確(que)保(bao)一個安(an)全的(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)環境，AAT3681A會檢(jian)查(cha)(cha)幾(ji)個條(tiao)件。輸入(ru)電(dian)(dian)源必須超(chao)過最小(xiao)工作電(dian)(dian)壓(ya)或欠壓(ya)鎖定閾(yu)值，才能(neng)啟動充(chong)(chong)(chong)電(dian)(dian)順(shun)序。當(dang)這些條(tiao)件都已(yi)得到滿足且電(dian)(dian)池(chi)(chi)連接(jie)到BAT引(yin)腳(jiao)，AAT3681A就檢(jian)查(cha)(cha)電(dian)(dian)池(chi)(chi)的(de)(de)(de)狀(zhuang)態。如果(guo)電(dian)(dian)池(chi)(chi)電(dian)(dian)壓(ya)低于預充(chong)(chong)(chong)電(dian)(dian)壓(ya)閾(yu)值，充(chong)(chong)(chong)電(dian)(dian)控制電(dian)(dian)路就開(kai)始對電(dian)(dian)池(chi)(chi)進行預充(chong)(chong)(chong)。電(dian)(dian)池(chi)(chi)預充(chong)(chong)(chong)涓流(liu)(liu)充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)是(shi)快(kuai)速充(chong)(chong)(chong)電(dian)(dian)恒流(liu)(liu)的(de)(de)(de)十(shi)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
在恒流快速充電(dian)(dian)(dian)階段，當(dang)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)到達輸出(chu)充電(dian)(dian)(dian)調節閾值時，系統就(jiu)進入恒壓(ya)充電(dian)(dian)(dian)模式。調節電(dian)(dian)(dian)壓(ya)水平在出(chu)廠時設置為(wei)4.2V(±0.5%)。恒壓(ya)模式下(xia)的充電(dian)(dian)(dian)電(dian)(dian)(dian)流掉下(xia)來，因為(wei)充電(dian)(dian)(dian)中的電(dian)(dian)(dian)池(chi)單元快到達其最大容量。
充電(dian)周期(qi)終結和再充電(dian)順(shun)序(xu)
在恒壓(ya)模式下，當(dang)充(chong)電(dian)(dian)電(dian)(dian)流掉(diao)到(dao)快速充(chong)電(dian)(dian)電(dian)(dian)流的10%時(shi)，該器(qi)件(jian)就終止充(chong)電(dian)(dian)，并進(jin)入(ru)睡眠(mian)(mian)狀態。充(chong)電(dian)(dian)器(qi)將保持(chi)睡眠(mian)(mian)狀態，直(zhi)到(dao)電(dian)(dian)池電(dian)(dian)壓(ya)降(jiang)到(dao)電(dian)(dian)池再充(chong)電(dian)(dian)壓(ya)閾值以下。
由(you)于在睡眠狀態下(xia)消(xiao)耗非常(chang)低(di)的電(dian)(dian)流，因此AAT3681A在不充電(dian)(dian)時(shi)可將(jiang)(jiang)電(dian)(dian)池泄(xie)露降到最低(di)。這(zhe)一(yi)特(te)性對這(zhe)樣一(yi)些(xie)應用來說特(te)別有用，其輸(shu)入(ru)(ru)電(dian)(dian)源水(shui)平(ping)可能低(di)于充電(dian)(dian)電(dian)(dian)池水(shui)平(ping)或(huo)欠壓(ya)鎖(suo)定(ding)水(shui)平(ping)。在這(zhe)些(xie)情況(kuang)下(xia)，當AAT3681A輸(shu)入(ru)(ru)電(dian)(dian)壓(ya)下(xia)降時(shi)，該器件將(jiang)(jiang)進入(ru)(ru)睡眠狀態，一(yi)旦輸(shu)入(ru)(ru)電(dian)(dian)源從錯誤狀態下(xia)恢(hui)復(fu)(fu)過來，它(ta)再自動恢(hui)復(fu)(fu)充電(dian)(dian)。
散熱考慮
AAT3681A采用SC70JW-8封裝(zhuang)，它(ta)能夠散發高達687mW的功率，當它(ta)被正確地安裝(zhuang)在(zai)PCB板上時(shi)，并具有最(zui)大160℃/W的熱阻。在(zai)設計(ji)PCB和(he)安排該(gai)充電(dian)器(qi)IC與某(mou)一(yi)特定應用設計(ji)中的其它(ta)散熱器(qi)件的位(wei)置(zhi)時(shi)，有許多因素(su)應當加以考慮。
該充電器IC的環(huan)境溫度(du)也將對電池充電應(ying)用的熱限(xian)制(zhi)有影響(xiang)。在某一特定環(huan)境條件下，可以(yi)期望的最大限(xian)制(zhi)可通過以(yi)下討論估計出來。
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(zui)大功耗(W)
θJA = 封裝熱阻(℃/W)
TJ(MAX) = 最大器(qi)件結溫(℃) [135℃]
TA = 環境溫(wen)度(℃)
其次，功耗可通過下式計算出來：
其中：
PD = 器件的總(zong)功耗
VIN = 輸入電壓
VBAT = BAT引腳上的(de)電(dian)池電(dian)壓
ICH = 針對某應用編程的(de)恒定充(chong)電電流(liu)
IOP = 在正常工作(zuo)狀(zhuang)態(tai)下充電器IC消耗的靜(jing)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。
總之，最(zui)壞的情況是充電器(qi)IC上的最(zui)大電壓(ya)降(jiang)，此時，電池(chi)電壓(ya)被充電到(dao)預充電壓(ya)閾值。
保(bao)(bao)護電(dian)路；過壓保(bao)(bao)護
一個過(guo)(guo)壓(ya)(ya)(ya)事件(jian)的(de)(de)定義為(wei)：BAT引腳上(shang)的(de)(de)電(dian)(dian)壓(ya)(ya)(ya)超(chao)過(guo)(guo)最大電(dian)(dian)池(chi)充電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)，并被設(she)定在(zai)過(guo)(guo)壓(ya)(ya)(ya)保護閾值。如果一個過(guo)(guo)壓(ya)(ya)(ya)事件(jian)發生，AAT3681A充電(dian)(dian)控(kong)制電(dian)(dian)路將關斷該器件(jian)，直到BAT引腳上(shang)的(de)(de)電(dian)(dian)壓(ya)(ya)(ya)掉到OVP電(dian)(dian)壓(ya)(ya)(ya)水平以(yi)下。AAT3681A在(zai)過(guo)(guo)壓(ya)(ya)(ya)狀態消除后，再恢復(fu)正常(chang)的(de)(de)充電(dian)(dian)操作。
保護電路(lu)；過熱關斷
AAT3681A有一個(ge)熱保護(hu)控制(zhi)電路(lu)，一旦內部裸片溫(wen)度(du)超過預(yu)置的(de)(de)熱限(xian)制(zhi)閾(yu)值，它就(jiu)關斷充(chong)電功(gong)能。一旦內部裸片溫(wen)度(du)掉到熱限(xian)制(zhi)以下，就(jiu)自(zi)動恢復到以前的(de)(de)正(zheng)常充(chong)電狀態。
充電電流的可編程性
用戶可借助一個放在ISET引腳與(yu)地之間的設置(zhi)電(dian)(dian)阻編(bian)程設定(ding)(ding)恒流充電(dian)(dian)水平。快速充電(dian)(dian)精度和預(yu)充涓(juan)流充電(dian)(dian)電(dian)(dian)流，由使用的設置(zhi)電(dian)(dian)阻的容差(cha)決定(ding)(ding)。因此，推薦采用1%容差(cha)的金屬薄(bo)膜電(dian)(dian)阻。快速充電(dian)(dian)恒流電(dian)(dian)流范圍從15mA到300mA。
AAT3681A可(ke)以即插即用(yong)方式提(ti)供電池充電器全部(bu)功(gong)能。它(ta)只需要(yao)一個外部(bu)元件就可(ke)以進行全部(bu)操作(zuo)。該器件可(ke)提(ti)供極(ji)出的性價比。2mm×2.1mm的小(xiao)占板面積(ji)可(ke)節省(sheng)PCB空間。該器件適合各(ge)種不同(tong)應用(yong)，從藍牙耳機(ji)、MP3播放器到腕表。AAT3681A是(shi)AnalogicTech公(gong)司(si)不同(tong)復雜度和類別產品大家(jia)庭的最新成員。