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(mu)前通常使用一(yi)種(zhong)線(xian)性充電(dian)(dian)器(qi)給這(zhe)種(zhong)電(dian)(dian)池(chi)充電(dian)(dian)，但這(zhe)種(zhong)充電(dian)(dian)器(qi)盡管(guan)操作更簡便和成本(ben)更低，但它有一(yi)個(ge)主(zhu)要缺(que)點：能(neng)耗太高。當輸入電(dian)(dian)壓為高和電(dian)(dian)池(chi)電(dian)(dian)壓為低(已放(fang)電(dian)(dian)電(dian)(dian)池(chi))時(shi)，線(xian)性充電(dian)(dian)器(qi)產(chan)生的熱(re)量足以損(sun)壞自(zi)身(shen)或其它鄰近元件(jian)。在本(ben)文(wen)中，凌特技(ji)術公司(si)提出了一(yi)種(zhong)替代方(fang)案，它可解決所有的過熱(re)問題而且充電(dian)(dian)快速。

　　當(dang)今許(xu)多靠電(dian)(dian)(dian)(dian)(dian)池供電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)手持設備都內建有(you)一(yi)個電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器。這(zhe)(zhe)些(xie)電(dian)(dian)(dian)(dian)(dian)池通(tong)常都為(wei)鋰離子電(dian)(dian)(dian)(dian)(dian)池，并且其(qi)功率密(mi)度可在范圍400mA小時(shi)(shi)(shi)到1.5A小時(shi)(shi)(shi)變化。你可以使用一(yi)種(zhong)(zhong)線性充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器給這(zhe)(zhe)種(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，而且這(zhe)(zhe)種(zhong)(zhong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器通(tong)常比基于(yu)轉換器的(de)(de)(de)(de)方案在外形上明顯更(geng)小，操作更(geng)簡(jian)便，成(cheng)本更(geng)低(di)，但(dan)它有(you)一(yi)個主要(yao)缺點：能耗太高。當(dang)輸入電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)高和電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)低(di)(已放(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池)時(shi)(shi)(shi)，線性充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器產生的(de)(de)(de)(de)熱量(liang)足(zu)以損壞(huai)自(zi)身或(huo)其(qi)它鄰近元件。典型地，這(zhe)(zhe)種(zhong)(zhong)狀態(即電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)隨充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)進行而升(sheng)高)只是(shi)(shi)(shi)暫時(shi)(shi)(shi)現象，但(dan)正是(shi)(shi)(shi)這(zhe)(zhe)些(xie)最(zui)糟糕的(de)(de)(de)(de)狀態需要(yao)設計師在決定充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)與IC溫度的(de)(de)(de)(de)最(zui)大(da)容許(xu)值時(shi)(shi)(shi)必須(xu)充(chong)(chong)(chong)分地加以考慮。當(dang)然(ran)，一(yi)種(zhong)(zhong)解決這(zhe)(zhe)種(zhong)(zhong)過熱問(wen)題的(de)(de)(de)(de)簡(jian)單方法(fa)是(shi)(shi)(shi)降低(di)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過程中整個恒流(liu)段的(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，但(dan)這(zhe)(zhe)種(zhong)(zhong)方法(fa)伴隨的(de)(de)(de)(de)問(wen)題是(shi)(shi)(shi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間的(de)(de)(de)(de)相(xiang)應(ying)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。

　　一個內部(bu)功率MOSFET允許編程(cheng)(cheng)設(she)定(ding)的(de)(de)(de)(de)(de)最(zui)大充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)可達1.5A，精度(du)(du)為7%，以(yi)確保(bao)(bao)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)快(kuai)速和(he)完(wan)全(quan)。這種內部(bu)MOSFET還可省掉一個外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)敏(min)(min)感電(dian)(dian)(dian)(dian)(dian)(dian)阻或遏(e)流(liu)(liu)二極管，最(zui)終的(de)(de)(de)(de)(de)無(wu)負載電(dian)(dian)(dian)(dian)(dian)(dian)壓是引腳可選(xuan)的(de)(de)(de)(de)(de)，或為4.1V或為 4.2V，精度(du)(du)是1%，這可防止過充(chong)帶來(lai)的(de)(de)(de)(de)(de)危險或欠充(chong)造成(cheng)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容量不足。遵從電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)制(zhi)造商的(de)(de)(de)(de)(de)使用(yong)(yong)(yong)要求，LTC1733包(bao)(bao)含了一個可編程(cheng)(cheng)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終止定(ding)時器(qi)(qi)和(he)熱(re)敏(min)(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻輸(shu)(shu)入(ru)，以(yi)保(bao)(bao)證充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)全(quan)過程(cheng)(cheng)的(de)(de)(de)(de)(de)溫度(du)(du)符合要求。狀態輸(shu)(shu)出包(bao)(bao)括：用(yong)(yong)(yong)以(yi)指(zhi)示充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)后(hou)期狀態的(de)(de)(de)(de)(de)C/10充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)檢測(ce)(ce)、決定(ding)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)是否可以(yi)進行下(xia)去的(de)(de)(de)(de)(de)壁式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)適(shi)配器(qi)(qi)狀態檢測(ce)(ce)、充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)監測(ce)(ce)、以(yi)及用(yong)(yong)(yong)以(yi)識(shi)別壞電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)錯誤檢測(ce)(ce)。低(di)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)調(diao)理電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(滴(di)充(chong))可安全(quan)地為過放電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，并自動續充(chong)以(yi)確保(bao)(bao)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)總能(neng)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)完(wan)全(quan)。當沒有壁式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)適(shi)配器(qi)(qi)或該部(bu)件關閉的(de)(de)(de)(de)(de)時候(hou)，為保(bao)(bao)持電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)能(neng)量， LTC1733的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)漏電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)降到5(A以(yi)下(xia)。

　　給電池充電
　　給單電(dian)(dian)(dian)(dian)池鋰離子電(dian)(dian)(dian)(dian)池系統充電(dian)(dian)(dian)(dian)時，用戶須在VCC腳(jiao)處(chu)施加至少4.5V的(de)輸入(ru)電(dian)(dian)(dian)(dian)壓。ACPR腳(jiao)隨后降為(wei)低(di)電(dian)(dian)(dian)(dian)平(ping)(pull low)，指(zhi)示輸入(ru)電(dian)(dian)(dian)(dian)壓條件(jian)已滿足(見圖2)。此(ci)外，必須用一(yi)個1%的(de)電(dian)(dian)(dian)(dian)阻器把(ba)PROG與(yu)GND相(xiang)連，使額定(ding)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流設(she)定(ding)為(wei)100V/RPROG。而后CHPG腳(jiao)為(wei)低(di)電(dian)(dian)(dian)(dian)平(ping)，指(zhi)示充電(dian)(dian)(dian)(dian)循環開(kai)始。TIMER和(he)GND之間用電(dian)(dian)(dian)(dian)容器連接，充電(dian)(dian)(dian)(dian)終止時間設(she)定(ding)為(wei)3小時/100nF。

　　如(ru)果在充電(dian)(dian)(dian)循環開(kai)始時(shi)BAT腳的(de)電(dian)(dian)(dian)壓(ya)(ya)低(di)于(yu)2.48V，那么，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)將為設(she)定(ding)值的(de)1/10，以(yi)使(shi)(shi)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)(ya)足(zu)夠(gou)高，安全實現(xian)全充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)(見圖3)。如(ru)果電(dian)(dian)(dian)池(chi)損壞(huai)，且在1/4的(de)設(she)定(ding)終止時(shi)間內電(dian)(dian)(dian)壓(ya)(ya)都升(sheng)不(bu)到2.48V以(yi)上(shang)，則(ze)充電(dian)(dian)(dian)循環終止，且FAULT狀態輸(shu)出將鎖存為低(di)電(dian)(dian)(dian)平(ping)，指示電(dian)(dian)(dian)池(chi)已壞(huai)。ACPR、CHRG和FAULT三個狀態輸(shu)出腳全都產(chan)生足(zu)夠(gou)的(de)電(dian)(dian)(dian)流(liu)衰弱(ruo)量，使(shi)(shi)LED亮燈。一旦電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)(ya)升(sheng)到2.48V以(yi)上(shang)(充電(dian)(dian)(dian)循環開(kai)始后不(bu)久會明顯表現(xian)出來(lai))，LTC1733將為電(dian)(dian)(dian)池(chi)提(ti)供(gong)由RPROG設(she)定(ding)的(de)恒定(ding)電(dian)(dian)(dian)流(liu)。LTC1733將一直(zhi)保(bao)持恒流(liu)模(mo)式(shi)，直(zhi)到BAT腳的(de)電(dian)(dian)(dian)壓(ya)(ya)接(jie)近所選擇的(de)最終浮置電(dian)(dian)(dian)壓(ya)(ya)(SEL=0V時(shi)為 4.1V ，SEL=VCC時(shi)為4.2V)為止。此后，器件進(jin)入(ru)恒壓(ya)(ya)模(mo)式(shi)。

　　在(zai)恒(heng)壓模(mo)式(shi)下，LTC1733將開始降低充電(dian)電(dian)流(liu)(liu)以保持(chi)BAT腳(jiao)的(de)恒(heng)壓而非恒(heng)流(liu)(liu)輸(shu)出(chu)。當電(dian)流(liu)(liu)降至最大設定充電(dian)電(dian)流(liu)(liu)的(de)10%時，內部(bu)比較(jiao)器會斷(duan)開CHRG腳(jiao)，并(bing)將一弱電(dian)流(liu)(liu)源(約(yue)25(A)接(jie)地(di)，以顯(xian)示接(jie)近充電(dian)結束(C/10)狀態。

　　與電流達到C/10時便結束充電過程的電池充電器不同(tong)，LTC1733在(zai)到(dao)達C/10點后，只要終止定時器時間不到(dao)，會繼(ji)續給電池(chi)(chi)充(chong)電，以保(bao)證電池(chi)(chi)完全充(chong)滿。在(zai)C/10處終止充(chong)電過程使電池(chi)(chi)只能充(chong)到(dao)其容量(liang)的90%到(dao)95%，而在(zai)C/10后繼(ji)續充(chong)并按(an)時間要求結束(shu)可使電池(chi)(chi)的容量(liang)充(chong)到(dao)100%。一旦充(chong)電結束(shu)，CHRG腳便呈現高阻抗(kang)狀態。

    電池的再充電
    假(jia)定在(zai)第一(yi)次充(chong)電(dian)(dian)(dian)(dian)(dian)時，電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)已充(chong)到(dao)了3.95V(SEL = 0V時) 或4.05V (SEL = VCC時)以上，那(nei)么(me)LTC1733可對電(dian)(dian)(dian)(dian)(dian)池進行再充(chong)電(dian)(dian)(dian)(dian)(dian)。一(yi)旦超出這些閾值，如果(guo)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)因電(dian)(dian)(dian)(dian)(dian)池負載的(de)(de)存在(zai)或電(dian)(dian)(dian)(dian)(dian)池的(de)(de)自放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流而掉到(dao)3.9V (SEL = 0V)或4.0V (SEL = VCC)以下時，則新一(yi)輪的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)循(xun)環(huan)開始了。再充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路(lu)集結BAT腳電(dian)(dian)(dian)(dian)(dian)壓(ya)數毫秒，以防止充(chong)電(dian)(dian)(dian)(dian)(dian)循(xun)環(huan)重啟造成的(de)(de)瞬態沖(chong)擊。

    熱調節
　　LTC1733的(de)另一個特性是具(ju)有內(nei)部(bu)熱調(diao)節(jie)回路。如(ru)果高(gao)(gao)功率操作或高(gao)(gao)的(de)環境溫(wen)(wen)(wen)(wen)度(du)導致(zhi)LTC1733的(de)溫(wen)(wen)(wen)(wen)度(du)接近105(C，那么充(chong)(chong)電電流(liu)(liu)會自動降低以將溫(wen)(wen)(wen)(wen)度(du)保(bao)持在105(C左(zuo)右 (板溫(wen)(wen)(wen)(wen)度(du)通常低于85(C)，這便是所謂(wei)的(de)恒(heng)溫(wen)(wen)(wen)(wen)模(mo)式(shi)。這一特性允許用(yong)戶基于具(ju)體的(de)工作條件設定充(chong)(chong)電電流(liu)(liu)，并去掉許多線性應用(yong)必需的(de)復(fu)雜過熱保(bao)護(hu)設計。

　　LTC1733會自動監視最糟(zao)狀態，這一特(te)性除(chu)可保護LTC1733外，還能(neng)(neng)去除(chu)板(ban)上的“熱點”區，從而(er)保護周邊元件。其(qi)它的電池充(chong)(chong)(chong)電器，其(qi)熱關閉特(te)性只是簡(jian)單地在極高溫度下(一般是150(C)關閉充(chong)(chong)(chong)電器而(er)已。這種基于溫度的關閉特(te)性允許電池充(chong)(chong)(chong)電器和周邊PCB板(ban)溫度升(sheng)至非常高，盡管(guan)具備關閉“保護”功能(neng)(neng)，但必須對應用進行仔(zi)細(xi)設計以避免(mian)到達熱關閉溫度。LTC1733通過自動均衡充(chong)(chong)(chong)電電流、散熱和工作(zuo)溫度，可使設計得到簡(jian)化。

　　為進一步改(gai)進LTC1733的(de)(de)熱調節性能，它采用(yong)了熱增強型(xing)MSOP封(feng)裝。其占用(yong)板面積可做到小于72 mm2，室溫功(gong)耗2W。這(zhe)相(xiang)當于用(yong)5V輸入電(dian)(dian)(dian)(dian)源實現最大(da)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流1.5A。這(zhe)里假定鋰(li)離子(zi)電(dian)(dian)(dian)(dian)池(chi)在充(chong)電(dian)(dian)(dian)(dian)大(da)部分時間里處于(3.7V狀(zhuang)態。實際上，由于典型(xing)的(de)(de)鋰(li)離子(zi)電(dian)(dian)(dian)(dian)池(chi)在充(chong)電(dian)(dian)(dian)(dian)開始幾分鐘內便(bian)升到3.8V以上，因(yin)此(ci)這(zhe)一假定有些保(bao)守。LTC1733的(de)(de)這(zhe)一獨(du)特熱特性和(he)7%的(de)(de)設定充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流精(jing)度，使單電(dian)(dian)(dian)(dian)池(chi)鋰(li)離子(zi)電(dian)(dian)(dian)(dian)池(chi)系統的(de)(de)充(chong)電(dian)(dian)(dian)(dian)過(guo)程非常迅速和(he)精(jing)確。

　　PROG電流監控器
　　在(zai)恒流(liu)(liu)模式下(xia)，PROG腳(jiao)(jiao)的(de)電(dian)壓(ya)總為1.5V，指(zhi)示設定的(de)充電(dian)電(dian)流(liu)(liu)從BAT腳(jiao)(jiao)流(liu)(liu)出。在(zai)恒溫或恒壓(ya)模式下(xia)，BAT腳(jiao)(jiao)的(de)電(dian)流(liu)(liu)有(you)所(suo)下(xia)降(jiang)。PROG腳(jiao)(jiao)與三個開(kai)漏狀(zhuang)態輸(shu)出(ACPR、CHRG和 FAULT)時刻通(tong)告用戶(hu)LTC1733到底在(zai)做(zuo)什么。

　　NTC熱敏電阻
　　除(chu)了可編程定(ding)時器(qi)和低的電池(chi)充電限定(ding)條件外，LTC1733在(zai)推薦給電池(chi)制造(zao)商的安全性特性列表(biao)中還增加了充電時的溫(wen)(wen)度限定(ding)。電池(chi)溫(wen)(wen)度通(tong)過緊貼電池(chi)組放置一只負溫(wen)(wen)度系數(NTC)熱(re)敏電阻來測(ce)定(ding)。借(jie)助IC中的內(nei)部(bu)溫(wen)(wen)度限制電路，LTC1733在(zai)電池(chi)溫(wen)(wen)度降到0(C以下或升到50(C以上時，可臨時停住內(nei)部(bu)定(ding)時器(qi)并(bing)停止(zhi)充電。實施這(zhe)一功(gong)能，選用(yong)RHOT的電阻值應與(yu)50(C下所(suo)用(yong)熱(re)敏電阻的阻值相同(tong)。這(zhe)樣將可以確保內(nei)部(bu)比較器(qi)的1/2VCC摔點(trip point)與(yu)NTC的50(C溫(wen)(wen)度相對應。

　　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(xing)能概要：