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，目前通常使用一(yi)種(zhong)線(xian)性充電(dian)器給這(zhe)種(zhong)電(dian)池(chi)充電(dian)，但這(zhe)種(zhong)充電(dian)器盡管操作更簡(jian)便和成本(ben)更低，但它有(you)一(yi)個主要缺點(dian)：能耗太高。當輸(shu)入電(dian)壓(ya)為高和電(dian)池(chi)電(dian)壓(ya)為低(已放電(dian)電(dian)池(chi))時，線(xian)性充電(dian)器產生的(de)熱量足以損(sun)壞自身或(huo)其它鄰近元件。在(zai)本(ben)文中，凌(ling)特技術公司提出(chu)了(le)一(yi)種(zhong)替(ti)代(dai)方案，它可(ke)解決所(suo)有(you)的(de)過熱問題而(er)且充電(dian)快(kuai)速。

　　當今許多靠電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)供電(dian)(dian)(dian)(dian)(dian)(dian)的(de)手(shou)持(chi)設備都內建有(you)(you)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)。這些(xie)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)通常都為鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)，并且其功(gong)率密度可在(zai)范圍400mA小(xiao)(xiao)時(shi)到1.5A小(xiao)(xiao)時(shi)變化。你可以(yi)使(shi)用一(yi)種(zhong)(zhong)線性充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)給這種(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，而(er)且這種(zhong)(zhong)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)通常比(bi)基于轉換器(qi)(qi)(qi)的(de)方案在(zai)外形上明顯更小(xiao)(xiao)，操作更簡便(bian)，成本更低(di)(di)，但它(ta)有(you)(you)一(yi)個(ge)主要(yao)缺點：能(neng)耗太高。當輸入電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為高和電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為低(di)(di)(已放電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi))時(shi)，線性充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)產生的(de)熱(re)量(liang)足以(yi)損壞自(zi)身或(huo)其它(ta)鄰近元件(jian)。典型地(di)，這種(zhong)(zhong)狀(zhuang)態(即電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)隨充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)進行而(er)升高)只是暫時(shi)現象，但正是這些(xie)最(zui)糟糕的(de)狀(zhuang)態需要(yao)設計師在(zai)決定充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)與IC溫度的(de)最(zui)大容許值時(shi)必(bi)須(xu)充(chong)分地(di)加以(yi)考慮。當然，一(yi)種(zhong)(zhong)解決這種(zhong)(zhong)過熱(re)問(wen)題的(de)簡單(dan)方法(fa)是降低(di)(di)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過程中整(zheng)個(ge)恒流(liu)段的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，但這種(zhong)(zhong)方法(fa)伴隨的(de)問(wen)題是充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間(jian)的(de)相應延長(chang)。

　　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)個內部(bu)功率MOSFET允許編程(cheng)設(she)定的(de)(de)最大充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)可(ke)達(da)1.5A，精度為(wei)(wei)7%，以(yi)(yi)(yi)確保(bao)(bao)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)快速和(he)完全(quan)。這種內部(bu)MOSFET還可(ke)省(sheng)掉一(yi)個外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)敏(min)感電(dian)(dian)(dian)(dian)(dian)(dian)阻或(huo)遏(e)流(liu)二極管(guan)，最終的(de)(de)無負載電(dian)(dian)(dian)(dian)(dian)(dian)壓是引腳可(ke)選的(de)(de)，或(huo)為(wei)(wei)4.1V或(huo)為(wei)(wei) 4.2V，精度是1%，這可(ke)防止(zhi)過充(chong)(chong)(chong)(chong)帶來的(de)(de)危險或(huo)欠充(chong)(chong)(chong)(chong)造成的(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)制造商的(de)(de)使用(yong)要(yao)求，LTC1733包(bao)含了一(yi)個可(ke)編程(cheng)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終止(zhi)定時(shi)器和(he)熱敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻輸入，以(yi)(yi)(yi)保(bao)(bao)證充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)全(quan)過程(cheng)的(de)(de)溫(wen)度符合要(yao)求。狀(zhuang)態(tai)輸出包(bao)括：用(yong)以(yi)(yi)(yi)指(zhi)示充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)后期狀(zhuang)態(tai)的(de)(de)C/10充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)檢(jian)(jian)測、決定充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)是否可(ke)以(yi)(yi)(yi)進(jin)行下去的(de)(de)壁(bi)式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)適配器狀(zhuang)態(tai)檢(jian)(jian)測、充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)監測、以(yi)(yi)(yi)及(ji)用(yong)以(yi)(yi)(yi)識別壞電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)錯誤檢(jian)(jian)測。低電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)調(diao)理電(dian)(dian)(dian)(dian)(dian)(dian)路(滴充(chong)(chong)(chong)(chong))可(ke)安全(quan)地(di)為(wei)(wei)過放電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，并自動續充(chong)(chong)(chong)(chong)以(yi)(yi)(yi)確保(bao)(bao)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)總能(neng)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)完全(quan)。當(dang)沒(mei)有壁(bi)式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)適配器或(huo)該(gai)部(bu)件(jian)關(guan)閉(bi)的(de)(de)時(shi)候，為(wei)(wei)保(bao)(bao)持電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)能(neng)量， LTC1733的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)漏(lou)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)降(jiang)到5(A以(yi)(yi)(yi)下。

　　給電池充電
　　給單電(dian)(dian)(dian)池(chi)鋰離子電(dian)(dian)(dian)池(chi)系(xi)統充(chong)(chong)電(dian)(dian)(dian)時(shi)，用(yong)戶須在(zai)VCC腳(jiao)處施(shi)加至少4.5V的(de)輸入電(dian)(dian)(dian)壓(ya)。ACPR腳(jiao)隨后降為低電(dian)(dian)(dian)平(pull low)，指(zhi)(zhi)示輸入電(dian)(dian)(dian)壓(ya)條件已滿(man)足(見圖2)。此外，必須用(yong)一個1%的(de)電(dian)(dian)(dian)阻器(qi)把PROG與(yu)GND相連(lian)，使額定(ding)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流設定(ding)為100V/RPROG。而后CHPG腳(jiao)為低電(dian)(dian)(dian)平，指(zhi)(zhi)示充(chong)(chong)電(dian)(dian)(dian)循(xun)環(huan)開始。TIMER和GND之間用(yong)電(dian)(dian)(dian)容器(qi)連(lian)接，充(chong)(chong)電(dian)(dian)(dian)終止時(shi)間設定(ding)為3小(xiao)時(shi)/100nF。

　　如果在(zai)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)循(xun)環(huan)(huan)開(kai)始(shi)時(shi)(shi)BAT腳的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低(di)于(yu)2.48V，那么，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)將(jiang)(jiang)為設定值的(de)(de)(de)(de)1/10，以使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)足夠高(gao)，安(an)全實現(xian)(xian)全充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(見(jian)圖3)。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池損壞，且在(zai)1/4的(de)(de)(de)(de)設定終止時(shi)(shi)間內電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)都升不到(dao)2.48V以上，則(ze)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)循(xun)環(huan)(huan)終止，且FAULT狀態輸出(chu)將(jiang)(jiang)鎖(suo)存為低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，指示電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池已(yi)壞。ACPR、CHRG和FAULT三(san)個狀態輸出(chu)腳全都產(chan)生足夠的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)衰弱量，使LED亮燈。一(yi)旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升到(dao)2.48V以上(充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)循(xun)環(huan)(huan)開(kai)始(shi)后(hou)不久會明顯表現(xian)(xian)出(chu)來)，LTC1733將(jiang)(jiang)為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池提供由RPROG設定的(de)(de)(de)(de)恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。LTC1733將(jiang)(jiang)一(yi)直(zhi)保持恒流(liu)模(mo)式，直(zhi)到(dao)BAT腳的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)接近所選(xuan)擇的(de)(de)(de)(de)最終浮置電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(SEL=0V時(shi)(shi)為 4.1V ，SEL=VCC時(shi)(shi)為4.2V)為止。此后(hou)，器(qi)件(jian)進入(ru)恒壓(ya)模(mo)式。

　　在恒壓模(mo)式下，LTC1733將開始降低(di)充(chong)電電流(liu)以保持BAT腳(jiao)(jiao)的恒壓而非恒流(liu)輸出。當(dang)電流(liu)降至(zhi)最大設定充(chong)電電流(liu)的10%時，內(nei)部比(bi)較器會(hui)斷開CHRG腳(jiao)(jiao)，并將一弱(ruo)電流(liu)源(yuan)(約25(A)接(jie)地，以顯(xian)示接(jie)近充(chong)電結(jie)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，LTC1733在到(dao)(dao)(dao)達C/10點后，只要終止定時器時間不到(dao)(dao)(dao)，會(hui)繼(ji)(ji)續給(gei)電(dian)(dian)池(chi)充電(dian)(dian)，以(yi)保證電(dian)(dian)池(chi)完全充滿。在C/10處終止充電(dian)(dian)過程使電(dian)(dian)池(chi)只能充到(dao)(dao)(dao)其(qi)容量的90%到(dao)(dao)(dao)95%，而在C/10后繼(ji)(ji)續充并(bing)按時間要求(qiu)結束(shu)可使電(dian)(dian)池(chi)的容量充到(dao)(dao)(dao)100%。一旦充電(dian)(dian)結束(shu)，CHRG腳(jiao)便(bian)呈(cheng)現高阻(zu)抗(kang)狀態(tai)。

    電池的再充電
    假定在第一次充(chong)電(dian)時，電(dian)池電(dian)壓(ya)已(yi)充(chong)到了(le)(le)3.95V(SEL = 0V時) 或(huo)4.05V (SEL = VCC時)以(yi)上，那么LTC1733可(ke)對電(dian)池進行再(zai)充(chong)電(dian)。一旦(dan)超出這(zhe)些(xie)閾值，如果電(dian)池電(dian)壓(ya)因電(dian)池負載的存在或(huo)電(dian)池的自放(fang)電(dian)電(dian)流(liu)而掉(diao)到3.9V (SEL = 0V)或(huo)4.0V (SEL = VCC)以(yi)下時，則新一輪的充(chong)電(dian)循(xun)環開始了(le)(le)。再(zai)充(chong)電(dian)電(dian)路集結BAT腳電(dian)壓(ya)數毫秒(miao)，以(yi)防(fang)止充(chong)電(dian)循(xun)環重(zhong)啟造成的瞬態(tai)沖(chong)擊。

    熱調節
　　LTC1733的(de)(de)另一個特性是具(ju)有內部熱(re)調節(jie)回路(lu)。如果高功率(lv)操作(zuo)或高的(de)(de)環境溫度(du)(du)導致LTC1733的(de)(de)溫度(du)(du)接近105(C，那么充電電流(liu)會自動降低以(yi)將溫度(du)(du)保持在(zai)105(C左(zuo)右 (板(ban)溫度(du)(du)通常(chang)低于(yu)(yu)85(C)，這(zhe)便(bian)是所(suo)謂(wei)的(de)(de)恒溫模式。這(zhe)一特性允許用戶基于(yu)(yu)具(ju)體(ti)的(de)(de)工作(zuo)條(tiao)件設(she)定(ding)充電電流(liu)，并去掉許多線性應用必需的(de)(de)復雜過熱(re)保護設(she)計。

　　LTC1733會(hui)自動監視(shi)最(zui)糟(zao)狀(zhuang)態，這一特(te)性(xing)除(chu)可保(bao)護(hu)(hu)LTC1733外，還能(neng)去除(chu)板上的(de)(de)“熱(re)點”區，從(cong)而保(bao)護(hu)(hu)周邊(bian)元件。其它的(de)(de)電池充電器，其熱(re)關(guan)閉(bi)特(te)性(xing)只(zhi)是簡單地在極高溫度下(一般(ban)是150(C)關(guan)閉(bi)充電器而已(yi)。這種基于(yu)溫度的(de)(de)關(guan)閉(bi)特(te)性(xing)允許電池充電器和(he)(he)周邊(bian)PCB板溫度升至非常高，盡(jin)管具備關(guan)閉(bi)“保(bao)護(hu)(hu)”功能(neng)，但必須對應用(yong)進(jin)行仔(zi)細設計(ji)以(yi)避免(mian)到(dao)(dao)達熱(re)關(guan)閉(bi)溫度。LTC1733通過(guo)自動均衡充電電流、散熱(re)和(he)(he)工作溫度，可使設計(ji)得到(dao)(dao)簡化。

　　為進一(yi)步改進LTC1733的(de)熱(re)調節性能，它采用(yong)(yong)了熱(re)增強(qiang)型MSOP封裝。其占用(yong)(yong)板面積可(ke)做(zuo)到(dao)小于(yu)(yu)72 mm2，室(shi)溫功耗2W。這(zhe)(zhe)相當于(yu)(yu)用(yong)(yong)5V輸入電(dian)(dian)源實現最大(da)充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)1.5A。這(zhe)(zhe)里(li)假(jia)定(ding)鋰離(li)子電(dian)(dian)池(chi)(chi)在充(chong)(chong)電(dian)(dian)大(da)部(bu)分時(shi)間里(li)處于(yu)(yu)(3.7V狀(zhuang)態。實際上，由于(yu)(yu)典型的(de)鋰離(li)子電(dian)(dian)池(chi)(chi)在充(chong)(chong)電(dian)(dian)開始幾分鐘內便升到(dao)3.8V以上，因(yin)此這(zhe)(zhe)一(yi)假(jia)定(ding)有些保守。LTC1733的(de)這(zhe)(zhe)一(yi)獨特(te)熱(re)特(te)性和7%的(de)設定(ding)充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)精度，使單電(dian)(dian)池(chi)(chi)鋰離(li)子電(dian)(dian)池(chi)(chi)系(xi)統的(de)充(chong)(chong)電(dian)(dian)過程非常迅速和精確。

　　PROG電流監控器
　　在(zai)恒(heng)流模式下(xia)，PROG腳(jiao)的電壓(ya)總為1.5V，指示設定的充電電流從BAT腳(jiao)流出。在(zai)恒(heng)溫或恒(heng)壓(ya)模式下(xia)，BAT腳(jiao)的電流有所下(xia)降。PROG腳(jiao)與三個開漏(lou)狀態輸(shu)出(ACPR、CHRG和 FAULT)時刻通告用戶LTC1733到底在(zai)做什么(me)。

　　NTC熱敏電阻
　　除了可編程(cheng)定(ding)(ding)時(shi)器和低的(de)電(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)限(xian)(xian)定(ding)(ding)條(tiao)件外，LTC1733在(zai)推薦給電(dian)池(chi)(chi)制造商的(de)安全性特性列表(biao)中還增加(jia)了充(chong)(chong)(chong)電(dian)時(shi)的(de)溫度限(xian)(xian)定(ding)(ding)。電(dian)池(chi)(chi)溫度通(tong)過緊貼電(dian)池(chi)(chi)組放置一只負溫度系數(shu)(NTC)熱敏(min)電(dian)阻(zu)來測定(ding)(ding)。借助IC中的(de)內部(bu)(bu)(bu)溫度限(xian)(xian)制電(dian)路，LTC1733在(zai)電(dian)池(chi)(chi)溫度降到0(C以下或升(sheng)到50(C以上時(shi)，可臨時(shi)停住內部(bu)(bu)(bu)定(ding)(ding)時(shi)器并停止(zhi)充(chong)(chong)(chong)電(dian)。實施這一功能，選(xuan)用RHOT的(de)電(dian)阻(zu)值應與(yu)50(C下所用熱敏(min)電(dian)阻(zu)的(de)阻(zu)值相(xiang)同。這樣將可以確保內部(bu)(bu)(bu)比較器的(de)1/2VCC摔(shuai)點(trip point)與(yu)NTC的(de)50(C溫度相(xiang)對(dui)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 性能概(gai)要：