便攜式電(dian)(dian)源(yuan)應用(yong)(yong)(yong)領域(yu)寬泛(fan)而多(duo)(duo)(duo)樣。產(chan)品(pin)涵蓋了從平均功(gong)耗僅幾 μW 的無線傳感(gan)器節點到采(cai)用(yong)(yong)(yong)好幾百瓦時電(dian)(dian)池(chi)組的車載(zai)式醫療或數據采(cai)集系統等眾(zhong)多(duo)(duo)(duo)門類。然而，盡管品(pin)種繁多(duo)(duo)(duo)，但它們(men)卻呈(cheng)現出了相對一致的發展(zhan)趨(qu)勢(shi) ━━ 設計人員不斷地(di)要(yao)(yao)求其產(chan)品(pin)擁有較高的功(gong)率以支持(chi)更多(duo)(duo)(duo)的功(gong)能，并指(zhi)望能從任何可用(yong)(yong)(yong)的電(dian)(dian)源(yuan)來給(gei)電(dian)(dian)池(chi)充電(dian)(dian)。第一個(ge)(ge)趨(qu)勢(shi)要(yao)(yao)求增加電(dian)(dian)池(chi)容量。不幸的是，用(yong)(yong)(yong)戶(hu)常常缺乏耐心，而且增加的電(dian)(dian)池(chi)容量必須要(yao)(yao)在合理的時間(jian)之內完成(cheng)充電(dian)(dian)，這(zhe)就必然導(dao)致充電(dian)(dian)電(dian)(dian)流的增大。第二個(ge)(ge)趨(qu)勢(shi)則要(yao)(yao)求電(dian)(dian)池(chi)充電(dian)(dian)解決方案具(ju)有巨大的靈活(huo)性。我們(men)將(jiang)對這(zhe)些問題逐(zhu)個(ge)(ge)進行較為詳細(xi)的探究。

　　更高的功率

　　新式的手持設備 (無論是消費類設備還是工業設備) 都有可能包括一個蜂窩電話調制解調器、一個WiFi模塊、一個藍牙模塊、一個大型的背面照明顯示器等等。許多手持式設備的電源架構都可通過蜂窩電話反映出來。通常，3.7V 的鋰離子電池因其很高的重量 (Wh/kg) 和體積 (Wh/m3) 能量密度而被用作主電源。過去，不少高功率密度設備都采用一個 7.4V 鋰離子電池以降低電(dian)(dian)(dian)(dian)流需求，但廉價(jia)的(de) 5V 電(dian)(dian)(dian)(dian)源(yuan)管理(li) IC 的(de)面(mian)市使(shi)得越來(lai)越多(duo)的(de)手持式(shi)設備轉而采用(yong)較低電(dian)(dian)(dian)(dian)壓架構。平板(ban)電(dian)(dian)(dian)(dian)腦很好地體現了(le)這一(yi)點 ━━ 標準的(de)平板(ban)電(dian)(dian)(dian)(dian)腦擁(yong)有豐(feng)富的(de)功能(neng)以及非常大 (用(yong)于便攜式(shi)設備) 的(de)屏幕(mu)。當采用(yong)一(yi)個 3.7V 電(dian)(dian)(dian)(dian)池來(lai)供電(dian)(dian)(dian)(dian)時，電(dian)(dian)(dian)(dian)池的(de)容(rong)量必須達到(dao)幾(ji)千mAh。為(wei)了(le)能(neng)夠在幾(ji)個小時之內完(wan)成此類(lei)電(dian)(dian)(dian)(dian)池的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)，需要(yao)幾(ji)千mA的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流。

　　然而，消費者同樣希望能(neng)夠在(zai)沒有可(ke)(ke)用(yong)的(de)大電(dian)(dian)(dian)流(liu)墻(qiang)上適配(pei)(pei)器(qi)(qi)(qi)時(shi)(shi)從一(yi)個(ge) USB 端口來為其(qi)高(gao)(gao)功(gong)率設備充(chong)(chong)電(dian)(dian)(dian)，這種愿望并未因為上述的(de)高(gao)(gao)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)而被(bei)遏制。為了滿足這些(xie)要求，在(zai)可(ke)(ke)以使用(yong)墻(qiang)上適配(pei)(pei)器(qi)(qi)(qi)時(shi)(shi)，電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)(qi)必須(xu)要能(neng)夠以高(gao)(gao)電(dian)(dian)(dian)流(liu) (>2A) 進行充(chong)(chong)電(dian)(dian)(dian)，但仍然可(ke)(ke)以高(gao)(gao)效地利(li)用(yong) USB 端口所提(ti)供的(de) 2.5W 至 4.5W 功(gong)率。此外，產品(pin)還必需避免(mian)敏感的(de)下游低電(dian)(dian)(dian)壓組件遭受(shou)有可(ke)(ke)能(neng)造(zao)成損(sun)壞的(de)過壓，將高(gao)(gao)電(dian)(dian)(dian)流(liu)從一(yi)個(ge) USB 輸入、一(yi)個(ge)墻(qiang)上適配(pei)(pei)器(qi)(qi)(qi)或電(dian)(dian)(dian)池無縫地引導至負載，并最大限(xian)度地降低功(gong)率損(sun)耗。與此同時(shi)(shi)，IC 必須(xu)安全(quan)地管(guan)理(li)電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)算(suan)法并監視關鍵(jian)的(de)系統(tong)參數。

　　解(jie)決單節電(dian)池(chi)供電(dian)型(xing)便攜式(shi)產(chan)品的電(dian)源難題

　　盡管似(si)乎無(wu)法找(zhao)到單個 IC 來(lai)滿足上述要求，但不妨(fang)考慮一下(xia)(xia) LTC4155，這(zhe)是(shi)一款(kuan)高(gao)功(gong)(gong)率、I2C 控制、高(gao)效(xiao)率 PowerPathTM管理器(qi)(qi)(qi)、理想(xiang)二極(ji)管控制器(qi)(qi)(qi)和鋰離子(zi)(zi)電(dian)池(chi)(chi)充(chong)電(dian)器(qi)(qi)(qi)。該器(qi)(qi)(qi)件(jian)(jian)設計(ji)用于從多(duo)種 5V 電(dian)源高(gao)效(xiao)地輸(shu)送高(gao)達 3A 的(de)電(dian)流，可(ke)(ke)為(wei)電(dian)池(chi)(chi)充(chong)電(dian)及系統用途提(ti)供 3.5A 以上的(de)電(dian)流。即使在(zai)這(zhe)些高(gao)電(dian)流水平(ping)下(xia)(xia)，LTC4155 的(de) 88% ~ 94% 效(xiao)率仍然可(ke)(ke)使熱預(yu)算限制條件(jian)(jian)有所放寬。LTC4155 的(de)開關 PowerPath 拓撲結構可(ke)(ke)對從兩個輸(shu)入電(dian)源 (比如：墻上適配器(qi)(qi)(qi)和 USB 端口) 至設備的(de)可(ke)(ke)再充(chong)電(dian)鋰離子(zi)(zi)電(dian)池(chi)(chi)的(de)功(gong)(gong)率輸(shu)送進(jin)行無(wu)縫管理，并在(zai)輸(shu)入功(gong)(gong)率有限時優先(xian)向(xiang)系統負載供電(dian)。

　　LTC4155 的開關穩壓器起一個變壓器的作用，允許 VOUT 上的負載電流超過輸入電源所吸收的電流，與常用的線性模式充電器相比，大幅度地改善了電池充電可用功率的使用效率。如前面的例子所示，LTC4155 能夠以高達 3.5A 的電流進行高效充電，從而縮短充電時間。與普通的開關電池充電器不同，LTC4155 具有“即時接通”操作能力(li)，以確保在(zai)插入電(dian)源(yuan)時可立即獲(huo)得系統功(gong)率，即使所采用的是一個失(shi)效的電(dian)池或深度(du)放電(dian)的電(dian)池也不例外。

　　在(zai)(zai)對電(dian)池(chi)進(jin)行高速充(chong)電(dian)時，監(jian)視電(dian)池(chi)的(de)(de)安全性(xing)是很重要的(de)(de)。LTC4155 將(jiang)在(zai)(zai)電(dian)池(chi)溫(wen)度下(xia)降至(zhi) 0℃ 以(yi)(yi)下(xia)或上升至(zhi) 40℃ 以(yi)(yi)上 (由(you)一(yi)個(ge)外(wai)(wai)部(bu)負(fu)溫(wen)度系數 [NTC] 熱敏電(dian)阻負(fu)責測量(liang)) 時自(zi)動停止充(chong)電(dian)。除了(le)這種(zhong)自(zi)主特性(xing)之外(wai)(wai)，LTC4155 還提供了(le)一(yi)個(ge) 7 位擴展標(biao)度模(mo)數轉(zhuan)換(huan)器 (ADC)，用(yong)于(yu)以(yi)(yi)大約 1℃ 的(de)(de)分辨率來監(jian)視電(dian)池(chi)的(de)(de)溫(wen)度。結合 4 種(zhong)可用(yong)的(de)(de)浮置電(dian)壓設定(ding)(ding)值和 15 種(zhong)電(dian)池(chi)充(chong)電(dian)電(dian)流設定(ding)(ding)值，該(gai) ADC 能夠用(yong)于(yu)建立基于(yu)電(dian)池(chi)溫(wen)度的(de)(de)定(ding)(ding)制充(chong)電(dian)算法。

　　通過一個簡單的二線式 I2C 端口可獲得 NTC ADC 結果，從而據此調整充電電流和電壓設定值。該I2C 端口還通過控制 16 種輸入電流限制設定值 (包括可兼容 USB 2.0 和 3.0 規格的設定值) 提供了與 USB 規范的兼容性。通信總線允許 LTC4155提供額外的狀態指示信息，例如：輸入電源狀態、充電器狀(zhuang)態和(he)故障(zhang)狀(zhuang)態。USB OTG (On-The-Go) 支持能(neng)力可(ke)在未(wei)采用任何附加組件的情況下提供一個返回 USB 端口的 5V 電源。

　　LTC4155 的(de)(de)雙輸入(ru)、優先(xian)(xian)級多(duo)路(lu)復用(yong)器可根據用(yong)戶定(ding)義(yi)的(de)(de)優先(xian)(xian)級 (適(shi)配器輸入(ru)是默認的(de)(de)優先(xian)(xian)選(xuan)擇) 自主選(xuan)擇最合適(shi)的(de)(de)輸入(ru) (墻上(shang)適(shi)配器或(huo)(huo) USB)。過壓保(bao)護 (OVP) 電路(lu)用(yong)于同時保(bao)護兩個輸入(ru)免遭(zao)因意外(wai)施加(jia)高電壓或(huo)(huo)反向電壓而(er)造(zao)成的(de)(de)損壞。LTC4155 的(de)(de)理想二(er)極管控(kong)制器可確保(bao)始終能夠向 VOUT 提(ti)供足(zu)(zu)夠的(de)(de)功(gong)(gong)率，即使輸入(ru)功(gong)(gong)率不(bu)(bu)足(zu)(zu)或(huo)(huo)缺失也不(bu)(bu)例(li)外(wai)。

　　對于(yu)諸如平板電(dian)(dian)腦或(huo)工業條形碼掃描(miao)儀(yi)等許(xu)多便(bian)攜(xie)式(shi)應用而言，管理兩個輸入 (例如：USB和墻上適配器) 就足(zu)夠了。不過，便(bian)攜(xie)式(shi)設備的設計人員(yuan)仍在(zai)繼續(xu)探尋能夠從任何可用電(dian)(dian)源來給電(dian)(dian)池充電(dian)(dian)的方法。

　　多種輸入電源

　　諸多(duo)(duo)原因(yin)(yin)導致用(yong)(yong)戶希望(wang)從多(duo)(duo)種輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。某(mou)些應(ying)用(yong)(yong)有可能(neng)需要脫離電(dian)(dian)(dian)(dian)(dian)(dian)(dian)網(wang)并指望(wang)由太陽能(neng)板(ban)來(lai)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。其他的(de)(de)應(ying)用(yong)(yong)則(ze)希望(wang)擁有能(neng)夠從墻(qiang)上(shang)適配器(qi)、汽車(che)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)或者高(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)工業(ye)或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源進行充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)便利(li)。不管(guan)是什么(me)原因(yin)(yin)，這種要求(qiu)都給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)系統施加(jia)了(le)一(yi)個沉重的(de)(de)負擔。大(da)(da)多(duo)(duo)數電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)均利(li)用(yong)(yong)一(yi)種降壓(ya)(ya) (開關或線性) 架構從一(yi)個高(gao)(gao)于(yu)最大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。早先(xian)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)產品通(tong)常被限制于(yu)大(da)(da)約(yue) 30V 的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。此(ci)類局限性導致設(she)計人員無法考慮將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源作(zuo)為可行的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，或者采用(yong)(yong)具(ju)有 42V 開路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)太陽能(neng)板(ban)。在(zai)某(mou)些場(chang)合中，期望(wang)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)范圍(wei)既會升至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以上(shang)也會降至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以下。設(she)計旨在(zai)應(ying)對上(shang)述難題的(de)(de)解決(jue)方(fang)案(an)通(tong)常需要整合高(gao)(gao)精(jing)度的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流檢測放大(da)(da)器(qi)、ADC、用(yong)(yong)于(yu)控制充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)操作(zuo)的(de)(de)微處理器(qi)、高(gao)(gao)性能(neng)的(de)(de) DC/DC 轉換(huan)器(qi)以及理想二極管(guan)或多(duo)(duo)路(lu)復用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。凌力爾特公司推出(chu)了(le)一(yi)款更(geng)加(jia)優越的(de)(de)解決(jue)方(fang)案(an)。

　　功能強大且擁有無可比(bi)擬之靈活性的充電解決方案

　　LTC4000 可將任何在外部補償的 DC/DC 電源轉換為一個全功能的電池充電器，并具有(you) PowerPathTM 控制功能。LTC4000 能夠驅動的(de)常用(yong)DC/DC 轉換器拓撲結構(gou)包括 (但(dan)不限于(yu)) 降(jiang)壓、升壓、降(jiang)壓-升壓、SEPIC 和反激(ji)式(shi)。該器件提供了精準的(de)輸入(ru)電(dian)(dian)流和充電(dian)(dian)電(dian)(dian)流調節(jie)，并可在一個(ge) 3V 至 60V 的(de)寬輸入(ru)和輸出電(dian)(dian)壓范圍內運(yun)作，因(yin)而(er)與多種不同(tong)的(de)輸入(ru)電(dian)(dian)壓電(dian)(dian)源、電(dian)(dian)池(chi)組(zu)尺寸和化(hua)學組(zu)成相兼容(rong)。由(you)于(yu)這款器件采用(yong)了通用(yong)型配(pei)置，因(yin)此其(qi)典型應用(yong)范圍十分廣泛，包括高功率電(dian)(dian)池(chi)充電(dian)(dian)器系(xi)統、高性(xing)能便攜式(shi)儀器、電(dian)(dian)池(chi)后備(bei)系(xi)統、配(pei)備(bei)電(dian)(dian)池(chi)的(de)工(gong)業(ye)設(she)備(bei)以及筆記本電(dian)(dian)腦 / 小型筆記本電(dian)(dian)腦等(deng)。

　　除了可支(zhi)持(chi)多種不同的 DC/DC 拓(tuo)撲(pu)結(jie)構之外，LTC4000 的高電(dian)(dian)(dian)(dian)壓能力(li)還使(shi)其能夠(gou)利用(yong)幾乎任何輸(shu)入(ru)(ru)(ru)(ru)電(dian)(dian)(dian)(dian)源來(lai)形(xing)成功(gong)能強(qiang)大(da)的電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)解決方案。為了確保(bao)來(lai)自這些輸(shu)入(ru)(ru)(ru)(ru)的功(gong)率能輸(shu)送至合適的負載，LTC4000采用(yong)了一種智能 PowerPathTM 拓(tuo)撲(pu)結(jie)構，當輸(shu)入(ru)(ru)(ru)(ru)功(gong)率有限時，該拓(tuo)撲(pu)結(jie)構將優先向系統負載供電(dian)(dian)(dian)(dian)。LTC4000 通過控制外部 PFET 來(lai)提供低(di)損耗(hao)反向電(dian)(dian)(dian)(dian)流(liu)保(bao)護、電(dian)(dian)(dian)(dian)池的低(di)損耗(hao)充電(dian)(dian)(dian)(dian)和放電(dian)(dian)(dian)(dian)以(yi)及(ji)“即(ji)(ji)時接通型”操作，以(yi)確保(bao)在插入(ru)(ru)(ru)(ru)電(dian)(dian)(dian)(dian)源時可立即(ji)(ji)獲得(de)系統功(gong)率，即(ji)(ji)使(shi)所采用(yong)的是一個失(shi)效的電(dian)(dian)(dian)(dian)池或深度放電(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)池也不例外。外部檢測電(dian)(dian)(dian)(dian)阻器可提供輸(shu)入(ru)(ru)(ru)(ru)電(dian)(dian)(dian)(dian)流(liu)和電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)信息，從而使(shi)得(de) LTC4000 能夠(gou)與功(gong)率范圍(wei)從幾毫瓦到幾千瓦的轉換器一起使(shi)用(yong)。

　　LTC4000 的(de)全功能電(dian)(dian)(dian)池充電(dian)(dian)(dian)控制器(qi)可(ke)對(dui)多種電(dian)(dian)(dian)池化學組成進行充電(dian)(dian)(dian)，包括鋰(li)離子電(dian)(dian)(dian)池 / 鋰(li)聚合(he)物電(dian)(dian)(dian)池 / 磷酸鐵(tie)鋰(li)電(dian)(dian)(dian)池、密封鉛酸電(dian)(dian)(dian)池 (SLA) 和鎳電(dian)(dian)(dian)池等。另(ling)外，電(dian)(dian)(dian)池充電(dian)(dian)(dian)器(qi)還具(ju)有高精度的(de)電(dian)(dian)(dian)流(liu)檢測(ce)功能，可(ke)為高電(dian)(dian)(dian)流(liu)應用提(ti)供(gong)較低的(de)檢測(ce)電(dian)(dian)(dian)壓。

　　新(xin)式(shi)便攜產(chan)品的(de)設計師從(cong)(cong)事(shi)著極(ji)富挑戰性的(de)工(gong)作 ━━ 特(te)別(bie)當其(qi)面(mian)對電(dian)(dian)(dian)(dian)源時(shi)。客戶不(bu)斷地(di)追逐需要消耗更多(duo)功率的(de)功能(neng)，因而必需使用更大的(de)電(dian)(dian)(dian)(dian)池。與(yu)此同時(shi)，客戶還希(xi)望擁有從(cong)(cong)幾乎所有的(de)可(ke)用電(dian)(dian)(dian)(dian)源來給這些(xie)電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)的(de)便利。雖然便攜式(shi)電(dian)(dian)(dian)(dian)源的(de)上(shang)述發展(zhan)趨勢帶來了設計難題，但 LTC4155 和(he) LTC4000 則使設計工(gong)作大為(wei)簡化(hua)。在低電(dian)(dian)(dian)(dian)壓系統中，LTC4155 可(ke)高(gao)效提供高(gao)達 3.5A 的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流，并具有諸多(duo)高(gao)性能(neng)特(te)性。LTC4000 能(neng)夠利用幾乎任何輸入來實現一款功能(neng)強大的(de)充(chong)電(dian)(dian)(dian)(dian)解(jie)決方案，且擁有無與(yu)倫(lun)比的(de)性能(neng)及(ji)靈活性。