當今許多靠鋰離子電池供電的手持設備都內建有一個電池充電器，目前通常使用(yong)一種(zhong)線性充(chong)電器(qi)給這(zhe)種(zhong)電池(chi)充(chong)電，但這(zhe)種(zhong)充(chong)電器(qi)盡管操作更(geng)簡便和成本更(geng)低(di)，但它(ta)有(you)一個主(zhu)要缺點：能耗太高(gao)。當(dang)輸入電壓為高(gao)和電池(chi)電壓為低(di)(已放電電池(chi))時，線性充(chong)電器(qi)產生的(de)(de)熱量足以(yi)損壞自(zi)身或其(qi)它(ta)鄰近元件。在本文中，凌(ling)特技術公(gong)司提出了一種(zhong)替代方案(an)，它(ta)可解決所(suo)有(you)的(de)(de)過熱問題而(er)且充(chong)電快速。

　　當(dang)今許多靠電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)手持設(she)備(bei)都內建有(you)一(yi)(yi)(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)。這(zhe)些電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)通(tong)(tong)常都為(wei)鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)，并且(qie)其(qi)功率密(mi)度可在范圍400mA小時到1.5A小時變化(hua)。你可以(yi)使用一(yi)(yi)(yi)種(zhong)線性(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)給(gei)這(zhe)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，而(er)且(qie)這(zhe)種(zhong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)通(tong)(tong)常比基于轉換器(qi)(qi)的(de)(de)(de)(de)(de)方案(an)在外(wai)形(xing)上(shang)明顯(xian)更(geng)小，操作更(geng)簡便，成本更(geng)低(di)，但(dan)它有(you)一(yi)(yi)(yi)個主要(yao)(yao)缺點：能耗太高。當(dang)輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)高和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)低(di)(已(yi)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi))時，線性(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)產生的(de)(de)(de)(de)(de)熱(re)量足以(yi)損壞自身(shen)或(huo)其(qi)它鄰近元(yuan)件。典型地，這(zhe)種(zhong)狀態(tai)(即電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓隨充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)進(jin)行而(er)升(sheng)高)只是(shi)(shi)暫時現象，但(dan)正(zheng)是(shi)(shi)這(zhe)些最糟糕的(de)(de)(de)(de)(de)狀態(tai)需要(yao)(yao)設(she)計師在決定充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)與IC溫度的(de)(de)(de)(de)(de)最大容許值時必(bi)須充(chong)(chong)(chong)分地加以(yi)考慮。當(dang)然，一(yi)(yi)(yi)種(zhong)解決這(zhe)種(zhong)過熱(re)問題(ti)的(de)(de)(de)(de)(de)簡單(dan)方法(fa)是(shi)(shi)降低(di)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程中整(zheng)個恒(heng)流(liu)(liu)段的(de)(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，但(dan)這(zhe)種(zhong)方法(fa)伴隨的(de)(de)(de)(de)(de)問題(ti)是(shi)(shi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間的(de)(de)(de)(de)(de)相應延長。

　　不過，凌特技術公司現在提出了一種替代方案，即LTC1733鋰離子單電池線性充電器，它解決了所有的過熱問題且充電快速。這種新穎的IC采用內部反饋來調節充電電流和限制裸片溫度。這意味著更快的充電時間，因為設計師可以通過編程設定一個很高充電電流，而且不會冒任何損壞IC或任何其它元件的風險。這一性能直接帶來的另一好處是毋需設計過熱保護電路。為了進一步改進熱傳遞性，LTC1733采用了熱增強型10針MSOP封裝。該IC只需要3個外部元件便可提供一個完整的鋰離子充電器解決方案。

　　一(yi)個內(nei)部(bu)(bu)功率MOSFET允許(xu)編程設定(ding)的(de)(de)最大充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)可達(da)1.5A，精度為7%，以(yi)(yi)確保(bao)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)快速和完全。這種(zhong)內(nei)部(bu)(bu)MOSFET還可省掉一(yi)個外(wai)部(bu)(bu)電(dian)(dian)(dian)(dian)流(liu)敏感電(dian)(dian)(dian)(dian)阻(zu)或(huo)(huo)遏流(liu)二極管，最終(zhong)的(de)(de)無負載電(dian)(dian)(dian)(dian)壓是(shi)引(yin)腳(jiao)可選的(de)(de)，或(huo)(huo)為4.1V或(huo)(huo)為 4.2V，精度是(shi)1%，這可防止過充(chong)(chong)(chong)帶來的(de)(de)危(wei)險或(huo)(huo)欠充(chong)(chong)(chong)造(zao)成的(de)(de)電(dian)(dian)(dian)(dian)池(chi)(chi)容量(liang)不(bu)足。遵從電(dian)(dian)(dian)(dian)池(chi)(chi)制(zhi)造(zao)商的(de)(de)使用(yong)要(yao)求，LTC1733包含(han)了一(yi)個可編程充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)終(zhong)止定(ding)時(shi)(shi)器和熱敏電(dian)(dian)(dian)(dian)阻(zu)輸(shu)入，以(yi)(yi)保(bao)證充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)全過程的(de)(de)溫度符(fu)合要(yao)求。狀態(tai)輸(shu)出包括：用(yong)以(yi)(yi)指示充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)后(hou)期狀態(tai)的(de)(de)C/10充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)檢測(ce)(ce)、決(jue)定(ding)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)是(shi)否(fou)可以(yi)(yi)進行(xing)下(xia)去的(de)(de)壁(bi)式電(dian)(dian)(dian)(dian)源(yuan)適(shi)配器狀態(tai)檢測(ce)(ce)、充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)監測(ce)(ce)、以(yi)(yi)及用(yong)以(yi)(yi)識別壞(huai)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)錯誤檢測(ce)(ce)。低電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)調理電(dian)(dian)(dian)(dian)路(滴充(chong)(chong)(chong))可安全地為過放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)，并自(zi)動續充(chong)(chong)(chong)以(yi)(yi)確保(bao)電(dian)(dian)(dian)(dian)池(chi)(chi)總能(neng)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)完全。當沒有壁(bi)式電(dian)(dian)(dian)(dian)源(yuan)適(shi)配器或(huo)(huo)該部(bu)(bu)件(jian)關閉的(de)(de)時(shi)(shi)候(hou)，為保(bao)持電(dian)(dian)(dian)(dian)池(chi)(chi)能(neng)量(liang)， LTC1733的(de)(de)電(dian)(dian)(dian)(dian)池(chi)(chi)漏電(dian)(dian)(dian)(dian)流(liu)降到5(A以(yi)(yi)下(xia)。

　　給電池充電
　　給(gei)單電(dian)池鋰離子電(dian)池系統充(chong)電(dian)時(shi)，用戶(hu)須在(zai)VCC腳(jiao)處(chu)施加至(zhi)少4.5V的輸入電(dian)壓。ACPR腳(jiao)隨后(hou)降為(wei)(wei)低電(dian)平(pull low)，指示輸入電(dian)壓條(tiao)件已滿(man)足(zu)(見圖2)。此外，必須用一個1%的電(dian)阻器把PROG與(yu)GND相連，使(shi)額定充(chong)電(dian)電(dian)流設定為(wei)(wei)100V/RPROG。而后(hou)CHPG腳(jiao)為(wei)(wei)低電(dian)平，指示充(chong)電(dian)循環開始(shi)。TIMER和GND之間(jian)用電(dian)容器連接，充(chong)電(dian)終止時(shi)間(jian)設定為(wei)(wei)3小時(shi)/100nF。

　　如果在充電(dian)(dian)(dian)(dian)(dian)(dian)循環開始時(shi)BAT腳的電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低于2.48V，那(nei)么，充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)將為設定(ding)值(zhi)的1/10，以(yi)使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)足夠(gou)(gou)高，安(an)全(quan)(quan)實現(xian)全(quan)(quan)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)(dian)(dian)(dian)(見圖3)。如果電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)損(sun)壞(huai)，且在1/4的設定(ding)終(zhong)止(zhi)時(shi)間內電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)都升不到(dao)2.48V以(yi)上(shang)，則(ze)充電(dian)(dian)(dian)(dian)(dian)(dian)循環終(zhong)止(zhi)，且FAULT狀(zhuang)態輸出(chu)將鎖存(cun)為低電(dian)(dian)(dian)(dian)(dian)(dian)平，指示電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)已壞(huai)。ACPR、CHRG和(he)FAULT三個狀(zhuang)態輸出(chu)腳全(quan)(quan)都產生足夠(gou)(gou)的電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)衰弱量(liang)，使(shi)LED亮燈。一旦電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升到(dao)2.48V以(yi)上(shang)(充電(dian)(dian)(dian)(dian)(dian)(dian)循環開始后不久會明(ming)顯表現(xian)出(chu)來(lai))，LTC1733將為電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提(ti)供(gong)由(you)RPROG設定(ding)的恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。LTC1733將一直保持恒流(liu)模式(shi)，直到(dao)BAT腳的電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)接近所選擇(ze)的最終(zhong)浮(fu)置電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(SEL=0V時(shi)為 4.1V ，SEL=VCC時(shi)為4.2V)為止(zhi)。此(ci)后，器件進入恒壓(ya)(ya)(ya)模式(shi)。

　　在恒壓模(mo)式下，LTC1733將開始(shi)降(jiang)低充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)以(yi)保持BAT腳(jiao)的(de)恒壓而非(fei)恒流(liu)輸(shu)出(chu)。當電(dian)(dian)(dian)流(liu)降(jiang)至最大設定(ding)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)10%時(shi)，內部(bu)比較器會(hui)斷開CHRG腳(jiao)，并將一弱電(dian)(dian)(dian)流(liu)源(約25(A)接(jie)地，以(yi)顯示接(jie)近充電(dian)(dian)(dian)結束(C/10)狀態(tai)。

　　與電流達到C/10時便結束充電過程的電池充電器不同，LTC1733在到(dao)達C/10點后，只要終(zhong)止定(ding)時(shi)器時(shi)間不到(dao)，會繼續給電(dian)池(chi)(chi)(chi)充電(dian)，以保證電(dian)池(chi)(chi)(chi)完全充滿。在C/10處終(zhong)止充電(dian)過程(cheng)使(shi)電(dian)池(chi)(chi)(chi)只能充到(dao)其容(rong)量(liang)的90%到(dao)95%，而(er)在C/10后繼續充并按(an)時(shi)間要求結(jie)束(shu)可使(shi)電(dian)池(chi)(chi)(chi)的容(rong)量(liang)充到(dao)100%。一(yi)旦充電(dian)結(jie)束(shu)，CHRG腳便呈(cheng)現高阻抗(kang)狀態。

    電池的再充電
    假定在第一(yi)次(ci)充電(dian)(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)已(yi)充到了3.95V(SEL = 0V時(shi)) 或4.05V (SEL = VCC時(shi))以上，那么LTC1733可對電(dian)(dian)(dian)(dian)(dian)池(chi)進行再充電(dian)(dian)(dian)(dian)(dian)。一(yi)旦超出這些閾值，如果電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)因電(dian)(dian)(dian)(dian)(dian)池(chi)負載的(de)(de)(de)存在或電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)自(zi)放(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流而掉到3.9V (SEL = 0V)或4.0V (SEL = VCC)以下時(shi)，則新一(yi)輪的(de)(de)(de)充電(dian)(dian)(dian)(dian)(dian)循環(huan)開始了。再充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路集(ji)結(jie)BAT腳電(dian)(dian)(dian)(dian)(dian)壓(ya)數毫秒，以防(fang)止充電(dian)(dian)(dian)(dian)(dian)循環(huan)重啟造(zao)成的(de)(de)(de)瞬態沖擊。

    熱調節
　　LTC1733的另一(yi)個特性是(shi)具(ju)有內(nei)部熱調(diao)節(jie)回路。如果高功率操作或高的環(huan)境溫(wen)度(du)(du)導(dao)致LTC1733的溫(wen)度(du)(du)接近(jin)105(C，那么充電電流會自動降低(di)以(yi)將溫(wen)度(du)(du)保持在(zai)105(C左右 (板溫(wen)度(du)(du)通常低(di)于(yu)85(C)，這(zhe)便(bian)是(shi)所(suo)謂的恒溫(wen)模式。這(zhe)一(yi)特性允許用(yong)戶(hu)基于(yu)具(ju)體的工作條(tiao)件(jian)設(she)定充電電流，并去(qu)掉許多(duo)線性應用(yong)必需的復(fu)雜過(guo)熱保護設(she)計。

　　LTC1733會自(zi)(zi)動監視(shi)最(zui)糟狀態(tai)，這一特(te)性除(chu)可保(bao)(bao)護(hu)(hu)LTC1733外(wai)，還(huan)能去(qu)除(chu)板上的“熱點”區，從而保(bao)(bao)護(hu)(hu)周邊元件(jian)。其它的電(dian)池充電(dian)器，其熱關閉特(te)性只是簡單(dan)地在極高溫(wen)(wen)(wen)度下(一般是150(C)關閉充電(dian)器而已。這種基(ji)于(yu)溫(wen)(wen)(wen)度的關閉特(te)性允許電(dian)池充電(dian)器和周邊PCB板溫(wen)(wen)(wen)度升至非(fei)常高，盡管具備關閉“保(bao)(bao)護(hu)(hu)”功能，但(dan)必須對應用進行仔細設(she)計(ji)以避免(mian)到(dao)達熱關閉溫(wen)(wen)(wen)度。LTC1733通過自(zi)(zi)動均衡(heng)充電(dian)電(dian)流、散熱和工作溫(wen)(wen)(wen)度，可使(shi)設(she)計(ji)得到(dao)簡化。

　　為進一步(bu)改進LTC1733的(de)(de)熱調節性(xing)能，它采用(yong)了(le)熱增強型MSOP封裝。其占用(yong)板面(mian)積可做(zuo)到(dao)小(xiao)于(yu)(yu)72 mm2，室(shi)溫功耗2W。這(zhe)相(xiang)當于(yu)(yu)用(yong)5V輸入電(dian)(dian)(dian)(dian)源實現最(zui)大(da)(da)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流1.5A。這(zhe)里假(jia)定鋰離子(zi)電(dian)(dian)(dian)(dian)池在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)大(da)(da)部分時間里處于(yu)(yu)(3.7V狀態。實際(ji)上，由(you)于(yu)(yu)典型的(de)(de)鋰離子(zi)電(dian)(dian)(dian)(dian)池在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)開始幾分鐘(zhong)內(nei)便升到(dao)3.8V以(yi)上，因此這(zhe)一假(jia)定有些保守(shou)。LTC1733的(de)(de)這(zhe)一獨特熱特性(xing)和7%的(de)(de)設定充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流精度，使單電(dian)(dian)(dian)(dian)池鋰離子(zi)電(dian)(dian)(dian)(dian)池系(xi)統的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)過程(cheng)非(fei)常迅速(su)和精確。

　　PROG電流監控器
　　在(zai)恒(heng)流模(mo)(mo)式下，PROG腳(jiao)(jiao)的電(dian)壓總為(wei)1.5V，指(zhi)示設定的充電(dian)電(dian)流從BAT腳(jiao)(jiao)流出。在(zai)恒(heng)溫或(huo)恒(heng)壓模(mo)(mo)式下，BAT腳(jiao)(jiao)的電(dian)流有所(suo)下降。PROG腳(jiao)(jiao)與(yu)三個開漏狀態輸出(ACPR、CHRG和(he) FAULT)時刻通告(gao)用戶LTC1733到底在(zai)做什么(me)。

　　NTC熱敏電阻
　　除了(le)可編程(cheng)定時器(qi)和低的(de)電(dian)池(chi)充(chong)電(dian)限(xian)定條(tiao)件(jian)外，LTC1733在(zai)推薦給電(dian)池(chi)制(zhi)造商的(de)安全性特(te)性列(lie)表(biao)中還增加了(le)充(chong)電(dian)時的(de)溫度(du)(du)限(xian)定。電(dian)池(chi)溫度(du)(du)通(tong)過緊貼電(dian)池(chi)組放置一只負溫度(du)(du)系數(NTC)熱(re)敏(min)電(dian)阻來測定。借助IC中的(de)內部(bu)溫度(du)(du)限(xian)制(zhi)電(dian)路，LTC1733在(zai)電(dian)池(chi)溫度(du)(du)降到0(C以(yi)(yi)下或升(sheng)到50(C以(yi)(yi)上時，可臨時停住內部(bu)定時器(qi)并停止充(chong)電(dian)。實施這(zhe)一功能，選用RHOT的(de)電(dian)阻值應(ying)與50(C下所用熱(re)敏(min)電(dian)阻的(de)阻值相同(tong)。這(zhe)樣將可以(yi)(yi)確(que)保內部(bu)比(bi)較(jiao)器(qi)的(de)1/2VCC摔(shuai)點(trip point)與NTC的(de)50(C溫度(du)(du)相對應(ying)。

　　還有，選定的NTC熱敏電阻在0(C時的阻值應盡量接近50(C時阻值的7倍。7：1的冷熱NTC比率可確保內部比較器7/8VCC的摔點與NTC 0(C的溫度相對應。每個熱和冷比較器都有約2(C的滯后以防摔點的振蕩。另外，NTC可以不使用任何外部元件，只簡單地通過將NTC腳接地就可使其功能失效。
 
　　結論
　　LTC1733是一種全功能的獨立鋰離子電池充電器。其結構極為簡單，只需要三個外部元件，就可安全精確地將高容量電池快充至1.5A的充電電流。在體現安全性及狀態特性方面，可加上一只NTC熱敏電阻和幾個LED。目前許多用鋰離子電池作供電電源的設備可采用這種類型的充電器，如數字靜態照相機(DSC)、個人數字助理(PDA)、蜂窩電話、MP3播放機以及GPS系統等。
 
　　值得注意的是，對上述諸多產品中有許多產品，有一種需求越來越強烈。就是通過ＵＳＢ接口插入一個主設備時，電池正在充電。盡管LTC1733可用于這類充電應用，但USB端口的可獲電流量有限，或500mA 或 100mA，依連接外設的數量而定。而在這些應用中LTC1733存在的一個缺陷是關閉模式下的靜態電流為0.9mA。這是一個難點，因為USB規范定義了一種暫停(SUSPEND)模式，即在USB+5V的情況下，漏電電流必須低于500(A。不過，凌特技術公司還有LTC4053，一種與USB兼容的鋰離子電池充電器。它在關閉模式下源電流僅為25(A。所以，當外設在USB請求暫停模式時，將中LTC4053，以滿足所要求的漏電電流限制。
 
    凌特公司（Linear Technology）推出獨立的開關模式鋰離子電池充電器 LTC4002，工作電源電壓可高達 24V，從而不需要 9V 和更高電壓墻上適配器所需的輸入瞬變保護。另外，器件的 4.7V 低輸入電源以及低壓差工作特性保證了 4.2V 鋰離子電池可從 5V 墻上適配器持續充電。為了實現安全自主的充電控制，LTC4002 還包括自動關機、電池預查驗、電池溫度檢測、充電結束指示以及一個充電 3 小時終止定時器等特性。
 
　　與遲滯拓樸結構充電器相比，LTC4002 恒定的 500kHz 工作頻率和電流模式結構允許使用更小的電感器和電容器。由于 100mV 的低檢測電壓，所以很容易達到超過86%。這種獨立的充電器有兩種封裝，3mm×3mm DFN 和 8 引線 SO。LTC4002 可應用于手持式儀表和通信裝置、充電座、便攜式計算機以及電池備份系統。
 
　　LTC4002 是一種高效率電流模式 PWM 控制器，開關頻率為 500kHz。它驅動一個外部 P 溝道 MOSFET，以最高 87% 的效率提供高達 2A 的充電電流。這種集成電路的恒定開關頻率將噪聲和濾波需求減至最低。配合使用各類輸出電容器（包括低 ESR 陶瓷電容器），LTC4002 都是穩定的。一個內部比較器檢測充電結束電流，而集成的定時器設定總充電時間，并在三小時后終止充電。LTC4002 自動進入休眠模式，使電池耗用電流降至 10uA。而且，當電池電壓降至 4.05V 以下時，這種集成電路還能自動開始充電
。
　　LTC4002 的工作溫度定在 －40°C 到 85°C。以 1000 片為單位批量購買，每片起價為 1.95美元。
 
　　LTC4002 性能概要：