便攜式(shi)電(dian)(dian)(dian)源應(ying)用(yong)領域寬泛而多樣(yang)。產(chan)品涵蓋了(le)從平均功耗僅幾(ji) μW 的(de)(de)無線(xian)傳感(gan)器節點(dian)到采(cai)用(yong)好幾(ji)百瓦時電(dian)(dian)(dian)池組(zu)的(de)(de)車載式(shi)醫(yi)療或(huo)數據采(cai)集系統等眾(zhong)多門類。然而，盡管(guan)品種繁多，但它們(men)卻呈現出了(le)相對一(yi)致的(de)(de)發展(zhan)趨(qu)(qu)勢(shi) ━━ 設計人員不斷(duan)地(di)要(yao)求其產(chan)品擁(yong)有較高的(de)(de)功率以(yi)支持(chi)更(geng)多的(de)(de)功能，并指望能從任何(he)可(ke)用(yong)的(de)(de)電(dian)(dian)(dian)源來給(gei)電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)。第一(yi)個趨(qu)(qu)勢(shi)要(yao)求增(zeng)加(jia)電(dian)(dian)(dian)池容量。不幸(xing)的(de)(de)是，用(yong)戶常(chang)常(chang)缺乏(fa)耐心，而且(qie)增(zeng)加(jia)的(de)(de)電(dian)(dian)(dian)池容量必須要(yao)在合理的(de)(de)時間之內完成充(chong)(chong)電(dian)(dian)(dian)，這就必然導致充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)(de)增(zeng)大(da)(da)。第二個趨(qu)(qu)勢(shi)則(ze)要(yao)求電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)解決方(fang)案具有巨(ju)大(da)(da)的(de)(de)靈活性(xing)。我們(men)將對這些問題逐個進行較為詳細的(de)(de)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)流需求，但廉價的(de) 5V 電(dian)(dian)源管理 IC 的(de)面市使得越(yue)來越(yue)多的(de)手持式(shi)設備轉而采(cai)用(yong)較低電(dian)(dian)壓架構。平(ping)(ping)板(ban)電(dian)(dian)腦很好(hao)地體(ti)現(xian)了這(zhe)一點 ━━ 標(biao)準的(de)平(ping)(ping)板(ban)電(dian)(dian)腦擁有豐(feng)富的(de)功能(neng)以及(ji)非(fei)常(chang)大 (用(yong)于便攜式(shi)設備) 的(de)屏幕。當采(cai)用(yong)一個 3.7V 電(dian)(dian)池(chi)(chi)來供電(dian)(dian)時，電(dian)(dian)池(chi)(chi)的(de)容量(liang)必(bi)須達到幾千mAh。為了能(neng)夠在幾個小時之內(nei)完成此(ci)類電(dian)(dian)池(chi)(chi)的(de)充(chong)電(dian)(dian)，需要幾千mA的(de)充(chong)電(dian)(dian)電(dian)(dian)流。

　　然(ran)而(er)，消(xiao)費者(zhe)同樣希望能夠在沒(mei)有可用的(de)(de)(de)大(da)電(dian)(dian)(dian)流(liu)墻上(shang)(shang)適(shi)配器(qi)時(shi)從一(yi)個(ge) USB 端口(kou)來為其高(gao)(gao)(gao)(gao)功率設備充(chong)(chong)電(dian)(dian)(dian)，這種(zhong)愿(yuan)望并未因(yin)為上(shang)(shang)述(shu)的(de)(de)(de)高(gao)(gao)(gao)(gao)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)而(er)被遏(e)制。為了滿足這些要求，在可以(yi)(yi)使用墻上(shang)(shang)適(shi)配器(qi)時(shi)，電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)器(qi)必(bi)須(xu)要能夠以(yi)(yi)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)流(liu) (>2A) 進行充(chong)(chong)電(dian)(dian)(dian)，但仍(reng)然(ran)可以(yi)(yi)高(gao)(gao)(gao)(gao)效地(di)(di)利用 USB 端口(kou)所提供的(de)(de)(de) 2.5W 至 4.5W 功率。此外(wai)，產品還(huan)必(bi)需(xu)避(bi)免敏感的(de)(de)(de)下游(you)低(di)(di)電(dian)(dian)(dian)壓(ya)組件遭受(shou)有可能造(zao)成損(sun)壞的(de)(de)(de)過(guo)壓(ya)，將高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)流(liu)從一(yi)個(ge) USB 輸入、一(yi)個(ge)墻上(shang)(shang)適(shi)配器(qi)或電(dian)(dian)(dian)池無縫地(di)(di)引(yin)導(dao)至負載，并最大(da)限度地(di)(di)降低(di)(di)功率損(sun)耗。與(yu)此同時(shi)，IC 必(bi)須(xu)安全地(di)(di)管理(li)電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)算法并監視關(guan)鍵的(de)(de)(de)系統參(can)數。

　　解決單(dan)節電(dian)池供電(dian)型(xing)便攜(xie)式產(chan)品的電(dian)源難題

　　盡(jin)管(guan)(guan)(guan)似(si)乎無法找(zhao)到單個 IC 來滿足(zu)上(shang)述要求(qiu)，但不妨考慮(lv)一(yi)下 LTC4155，這(zhe)是一(yi)款(kuan)高功(gong)率、I2C 控(kong)制、高效(xiao)率 PowerPathTM管(guan)(guan)(guan)理(li)器、理(li)想二極管(guan)(guan)(guan)控(kong)制器和鋰離(li)子電(dian)池充電(dian)器。該器件(jian)設(she)計用于從多種 5V 電(dian)源(yuan)高效(xiao)地(di)輸送高達 3A 的電(dian)流，可(ke)為電(dian)池充電(dian)及系統(tong)用途(tu)提(ti)供 3.5A 以上(shang)的電(dian)流。即使在這(zhe)些(xie)高電(dian)流水平下，LTC4155 的 88% ~ 94% 效(xiao)率仍然(ran)可(ke)使熱預(yu)算限(xian)制條(tiao)件(jian)有所放寬。LTC4155 的開關 PowerPath 拓撲結(jie)構(gou)可(ke)對從兩個輸入(ru)電(dian)源(yuan) (比如：墻上(shang)適配(pei)器和 USB 端(duan)口(kou)) 至(zhi)設(she)備的可(ke)再(zai)充電(dian)鋰離(li)子電(dian)池的功(gong)率輸送進行無縫管(guan)(guan)(guan)理(li)，并在輸入(ru)功(gong)率有限(xian)時優先(xian)向系統(tong)負(fu)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(shi)接(jie)通”操作(zuo)能力，以(yi)確保(bao)在插入電(dian)源時(shi)可立即獲(huo)得(de)系統(tong)功率，即使所采用(yong)的是一(yi)個失(shi)效(xiao)的電(dian)池或(huo)深度放電(dian)的電(dian)池也不例外。

　　在(zai)(zai)對電(dian)(dian)池(chi)進行(xing)高速充電(dian)(dian)時(shi)(shi)，監視電(dian)(dian)池(chi)的(de)(de)(de)安(an)全(quan)性是很重要的(de)(de)(de)。LTC4155 將在(zai)(zai)電(dian)(dian)池(chi)溫(wen)(wen)度下降至 0℃ 以下或上升至 40℃ 以上 (由一(yi)(yi)個外部負溫(wen)(wen)度系數 [NTC] 熱敏電(dian)(dian)阻(zu)負責測(ce)量) 時(shi)(shi)自(zi)(zi)動停止(zhi)充電(dian)(dian)。除了(le)這(zhe)種(zhong)自(zi)(zi)主特(te)性之(zhi)外，LTC4155 還提供(gong)了(le)一(yi)(yi)個 7 位擴(kuo)展(zhan)標度模數轉(zhuan)換器 (ADC)，用于以大(da)約 1℃ 的(de)(de)(de)分辨率來監視電(dian)(dian)池(chi)的(de)(de)(de)溫(wen)(wen)度。結合 4 種(zhong)可(ke)用的(de)(de)(de)浮置電(dian)(dian)壓設(she)定值(zhi)(zhi)和 15 種(zhong)電(dian)(dian)池(chi)充電(dian)(dian)電(dian)(dian)流設(she)定值(zhi)(zhi)，該 ADC 能夠用于建立基于電(dian)(dian)池(chi)溫(wen)(wen)度的(de)(de)(de)定制充電(dian)(dian)算法(fa)。

　　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、充電器狀態(tai)和故障(zhang)狀態(tai)。USB OTG (On-The-Go) 支(zhi)持能(neng)力可在未采用任何附(fu)加組件(jian)的情(qing)況下提供一個(ge)返回 USB 端口的 5V 電源。

　　LTC4155 的雙輸(shu)入(ru)(ru)(ru)、優先(xian)級多(duo)路(lu)復用器可根據用戶定義的優先(xian)級 (適配器輸(shu)入(ru)(ru)(ru)是默認的優先(xian)選擇) 自主選擇最合(he)適的輸(shu)入(ru)(ru)(ru) (墻(qiang)上適配器或(huo) USB)。過壓(ya)保護 (OVP) 電(dian)路(lu)用于同時保護兩個輸(shu)入(ru)(ru)(ru)免遭因意(yi)外施加高電(dian)壓(ya)或(huo)反向(xiang)(xiang)電(dian)壓(ya)而(er)造成的損(sun)壞(huai)。LTC4155 的理想(xiang)二(er)極管控(kong)制器可確保始(shi)終能夠(gou)向(xiang)(xiang) VOUT 提供足夠(gou)的功率(lv)，即使(shi)輸(shu)入(ru)(ru)(ru)功率(lv)不(bu)足或(huo)缺失也不(bu)例(li)外。

　　對于諸如平板電腦或工(gong)業條(tiao)形碼掃描(miao)儀等(deng)許(xu)多便攜式應用而言，管理(li)兩個輸(shu)入(ru) (例如：USB和墻上(shang)適配器) 就足夠(gou)了。不過，便攜式設備的設計(ji)人員仍(reng)在繼續探尋能夠(gou)從任何(he)可(ke)用電源來給電池(chi)充(chong)電的方法。

　　多種輸入電源

　　諸多原因導致用(yong)(yong)戶希(xi)望從(cong)多種(zhong)(zhong)輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。某(mou)些(xie)應(ying)(ying)用(yong)(yong)有(you)可能(neng)(neng)需要(yao)脫離電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)網并指望由太陽能(neng)(neng)板來供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。其(qi)他(ta)的(de)(de)(de)(de)應(ying)(ying)用(yong)(yong)則希(xi)望擁(yong)有(you)能(neng)(neng)夠從(cong)墻上適配器、汽車電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)或(huo)者(zhe)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)工(gong)業或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)信電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源進行充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)便利。不管是什么原因，這(zhe)種(zhong)(zhong)要(yao)求(qiu)都給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)系(xi)統施加(jia)了一(yi)個(ge)沉重(zhong)的(de)(de)(de)(de)負擔。大(da)(da)多數電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器均利用(yong)(yong)一(yi)種(zhong)(zhong)降壓(ya) (開(kai)關(guan)或(huo)線性) 架構從(cong)一(yi)個(ge)高(gao)于(yu)最大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。早先的(de)(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器產品通常(chang)被(bei)限制于(yu)大(da)(da)約 30V 的(de)(de)(de)(de)輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。此類局限性導致設計(ji)人員無法考慮將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)信電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源作(zuo)(zuo)為可行的(de)(de)(de)(de)輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，或(huo)者(zhe)采用(yong)(yong)具有(you) 42V 開(kai)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)太陽能(neng)(neng)板。在某(mou)些(xie)場合中，期望輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)范圍既會升至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以(yi)上也會降至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以(yi)下。設計(ji)旨在應(ying)(ying)對(dui)上述難題的(de)(de)(de)(de)解(jie)決(jue)方案通常(chang)需要(yao)整合高(gao)精度的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流檢測放大(da)(da)器、ADC、用(yong)(yong)于(yu)控制充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)操作(zuo)(zuo)的(de)(de)(de)(de)微處理器、高(gao)性能(neng)(neng)的(de)(de)(de)(de) DC/DC 轉換器以(yi)及理想二(er)極管或(huo)多路(lu)復用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。凌力爾(er)特公司推(tui)出了一(yi)款更加(jia)優越的(de)(de)(de)(de)解(jie)決(jue)方案。

　　功能強(qiang)大且擁有無可比擬之靈(ling)活性的(de)充(chong)電解決方(fang)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 PowerPathTM 控制功(gong)能。LTC4000 能夠驅(qu)動的(de)常用(yong)DC/DC 轉換(huan)器(qi)(qi)拓撲結構(gou)包括 (但不限(xian)于(yu)) 降壓(ya)、升(sheng)壓(ya)、降壓(ya)-升(sheng)壓(ya)、SEPIC 和(he)反激式(shi)。該器(qi)(qi)件提供(gong)了精準的(de)輸入(ru)(ru)電(dian)(dian)流和(he)充電(dian)(dian)電(dian)(dian)流調節，并可在一個 3V 至(zhi) 60V 的(de)寬輸入(ru)(ru)和(he)輸出電(dian)(dian)壓(ya)范(fan)(fan)圍內(nei)運作，因而(er)與多種不同的(de)輸入(ru)(ru)電(dian)(dian)壓(ya)電(dian)(dian)源、電(dian)(dian)池(chi)組(zu)尺寸和(he)化學組(zu)成相兼容。由于(yu)這款(kuan)器(qi)(qi)件采用(yong)了通用(yong)型(xing)(xing)配置，因此(ci)其(qi)典型(xing)(xing)應用(yong)范(fan)(fan)圍十分廣泛，包括高功(gong)率(lv)電(dian)(dian)池(chi)充電(dian)(dian)器(qi)(qi)系統、高性(xing)能便攜式(shi)儀器(qi)(qi)、電(dian)(dian)池(chi)后(hou)備(bei)系統、配備(bei)電(dian)(dian)池(chi)的(de)工(gong)業設備(bei)以及(ji)筆(bi)記本(ben)電(dian)(dian)腦 / 小(xiao)型(xing)(xing)筆(bi)記本(ben)電(dian)(dian)腦等。

　　除了可支持多種不同的 DC/DC 拓撲結(jie)構(gou)之外，LTC4000 的高電(dian)(dian)(dian)(dian)壓能(neng)(neng)(neng)力還(huan)使其能(neng)(neng)(neng)夠(gou)利(li)用(yong)(yong)幾乎任何(he)輸(shu)入電(dian)(dian)(dian)(dian)源(yuan)來(lai)形成(cheng)功能(neng)(neng)(neng)強大的電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)解決方案。為(wei)了確保來(lai)自(zi)這些輸(shu)入的功率(lv)能(neng)(neng)(neng)輸(shu)送至(zhi)合(he)適的負(fu)(fu)載，LTC4000采用(yong)(yong)了一種智(zhi)能(neng)(neng)(neng) PowerPathTM 拓撲結(jie)構(gou)，當輸(shu)入功率(lv)有限(xian)時，該拓撲結(jie)構(gou)將優先向系統負(fu)(fu)載供電(dian)(dian)(dian)(dian)。LTC4000 通(tong)過控制外部 PFET 來(lai)提(ti)供低(di)損(sun)耗反向電(dian)(dian)(dian)(dian)流(liu)保護、電(dian)(dian)(dian)(dian)池(chi)的低(di)損(sun)耗充(chong)(chong)電(dian)(dian)(dian)(dian)和放(fang)電(dian)(dian)(dian)(dian)以(yi)及“即(ji)(ji)時接通(tong)型(xing)”操作(zuo)，以(yi)確保在插入電(dian)(dian)(dian)(dian)源(yuan)時可立即(ji)(ji)獲(huo)得(de)系統功率(lv)，即(ji)(ji)使所采用(yong)(yong)的是一個失效的電(dian)(dian)(dian)(dian)池(chi)或深(shen)度放(fang)電(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)池(chi)也不例外。外部檢測電(dian)(dian)(dian)(dian)阻器(qi)可提(ti)供輸(shu)入電(dian)(dian)(dian)(dian)流(liu)和電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)信息，從(cong)而(er)使得(de) LTC4000 能(neng)(neng)(neng)夠(gou)與(yu)功率(lv)范(fan)圍從(cong)幾毫(hao)瓦到幾千瓦的轉換器(qi)一起使用(yong)(yong)。

　　LTC4000 的全功能電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)控制器(qi)可(ke)對多種電(dian)(dian)(dian)池(chi)(chi)化學組成進行充(chong)電(dian)(dian)(dian)，包括鋰離子電(dian)(dian)(dian)池(chi)(chi) / 鋰聚合物電(dian)(dian)(dian)池(chi)(chi) / 磷酸鐵鋰電(dian)(dian)(dian)池(chi)(chi)、密封鉛酸電(dian)(dian)(dian)池(chi)(chi) (SLA) 和鎳(nie)電(dian)(dian)(dian)池(chi)(chi)等。另(ling)外，電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)器(qi)還具有高(gao)精度的電(dian)(dian)(dian)流檢測功能，可(ke)為(wei)高(gao)電(dian)(dian)(dian)流應(ying)用提供較低的檢測電(dian)(dian)(dian)壓(ya)。

　　新式便攜產品的(de)(de)設計師從(cong)事(shi)著極(ji)富挑戰性(xing)(xing)的(de)(de)工(gong)作 ━━ 特(te)別當(dang)其面對電(dian)源(yuan)時(shi)。客戶不斷地追逐需(xu)要消耗更多功(gong)率的(de)(de)功(gong)能(neng)(neng)(neng)，因而(er)必需(xu)使用更大(da)的(de)(de)電(dian)池。與此同時(shi)，客戶還希望(wang)擁(yong)有從(cong)幾乎(hu)所(suo)有的(de)(de)可用電(dian)源(yuan)來給這些電(dian)池充電(dian)的(de)(de)便利(li)。雖然便攜式電(dian)源(yuan)的(de)(de)上(shang)述發(fa)展趨勢(shi)帶來了設計難題，但 LTC4155 和(he) LTC4000 則(ze)使設計工(gong)作大(da)為簡化。在低電(dian)壓系統中(zhong)，LTC4155 可高效提供高達 3.5A 的(de)(de)充電(dian)電(dian)流，并具有諸多高性(xing)(xing)能(neng)(neng)(neng)特(te)性(xing)(xing)。LTC4000 能(neng)(neng)(neng)夠(gou)利(li)用幾乎(hu)任何輸入來實現一款功(gong)能(neng)(neng)(neng)強大(da)的(de)(de)充電(dian)解(jie)決方(fang)案，且擁(yong)有無與倫比(bi)的(de)(de)性(xing)(xing)能(neng)(neng)(neng)及靈活性(xing)(xing)。