便攜式電(dian)(dian)(dian)源(yuan)應用領域寬泛而多樣(yang)。產(chan)品(pin)涵蓋了從(cong)(cong)平均功耗僅幾 μW 的(de)(de)(de)(de)無線傳感(gan)器節點到采用好幾百瓦時(shi)電(dian)(dian)(dian)池(chi)(chi)組的(de)(de)(de)(de)車載式醫療或數據采集系(xi)統等眾多門類。然而，盡管品(pin)種繁多，但它們(men)(men)卻呈現(xian)出(chu)了相對一致的(de)(de)(de)(de)發展趨勢(shi) ━━ 設計人員不斷地要求(qiu)(qiu)其產(chan)品(pin)擁有較高(gao)的(de)(de)(de)(de)功率以支持更多的(de)(de)(de)(de)功能(neng)，并指(zhi)望能(neng)從(cong)(cong)任(ren)何可用的(de)(de)(de)(de)電(dian)(dian)(dian)源(yuan)來給(gei)電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)。第(di)一個趨勢(shi)要求(qiu)(qiu)增加電(dian)(dian)(dian)池(chi)(chi)容量。不幸的(de)(de)(de)(de)是，用戶常常缺乏耐心，而且(qie)增加的(de)(de)(de)(de)電(dian)(dian)(dian)池(chi)(chi)容量必須要在(zai)合理(li)的(de)(de)(de)(de)時(shi)間之內完成(cheng)充(chong)電(dian)(dian)(dian)，這就必然導致充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)(de)(de)(de)增大。第(di)二(er)個趨勢(shi)則要求(qiu)(qiu)電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)解決方案具(ju)有巨大的(de)(de)(de)(de)靈活性。我們(men)(men)將(jiang)對這些問題(ti)逐個進行較為詳細(xi)的(de)(de)(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(yi)降低電(dian)流需(xu)(xu)求，但廉價的(de) 5V 電(dian)源管理 IC 的(de)面(mian)市使(shi)得越來越多的(de)手持(chi)式設備轉而采用較低電(dian)壓架構。平板電(dian)腦很好(hao)地(di)體現了這一點 ━━ 標(biao)準的(de)平板電(dian)腦擁(yong)有豐富的(de)功能以(yi)及非常大 (用于便攜式設備) 的(de)屏幕。當采用一個 3.7V 電(dian)池(chi)來供電(dian)時(shi)，電(dian)池(chi)的(de)容(rong)量必須(xu)達到幾千mAh。為(wei)了能夠在(zai)幾個小時(shi)之內完成此(ci)類電(dian)池(chi)的(de)充電(dian)，需(xu)(xu)要幾千mA的(de)充電(dian)電(dian)流。

　　然(ran)(ran)而，消費(fei)者同(tong)樣希望(wang)能夠(gou)(gou)在沒(mei)有可(ke)用的(de)(de)大(da)電(dian)流墻上(shang)適(shi)配器(qi)時(shi)從一個 USB 端口(kou)來為其(qi)高功率(lv)設備充(chong)(chong)電(dian)，這(zhe)種愿望(wang)并未因為上(shang)述的(de)(de)高充(chong)(chong)電(dian)電(dian)流而被遏制。為了滿(man)足這(zhe)些要(yao)求，在可(ke)以使用墻上(shang)適(shi)配器(qi)時(shi)，電(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)器(qi)必須要(yao)能夠(gou)(gou)以高電(dian)流 (>2A) 進行充(chong)(chong)電(dian)，但仍然(ran)(ran)可(ke)以高效地(di)利(li)用 USB 端口(kou)所(suo)提供的(de)(de) 2.5W 至 4.5W 功率(lv)。此外，產品還(huan)必需避免敏感的(de)(de)下游低(di)(di)電(dian)壓(ya)組件遭受(shou)有可(ke)能造成損(sun)壞(huai)的(de)(de)過壓(ya)，將(jiang)高電(dian)流從一個 USB 輸入(ru)、一個墻上(shang)適(shi)配器(qi)或電(dian)池(chi)(chi)(chi)無縫(feng)地(di)引導至負載(zai)，并最大(da)限度(du)地(di)降低(di)(di)功率(lv)損(sun)耗。與此同(tong)時(shi)，IC 必須安全地(di)管理電(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)算法并監(jian)視關鍵的(de)(de)系統(tong)參(can)數。

　　解決單節電(dian)池供電(dian)型便(bian)攜式產品的電(dian)源難題

　　盡管似乎無(wu)法找到單個(ge) IC 來滿足上(shang)(shang)述要求，但不妨考慮一(yi)下 LTC4155，這是一(yi)款高功(gong)(gong)率(lv)、I2C 控制(zhi)、高效率(lv) PowerPathTM管理器(qi)(qi)、理想(xiang)二極管控制(zhi)器(qi)(qi)和(he)鋰離子電(dian)池充電(dian)器(qi)(qi)。該(gai)器(qi)(qi)件設計用于從多種 5V 電(dian)源(yuan)高效地輸(shu)(shu)送高達 3A 的電(dian)流(liu)，可為(wei)電(dian)池充電(dian)及系統(tong)用途提供(gong) 3.5A 以上(shang)(shang)的電(dian)流(liu)。即使在這些高電(dian)流(liu)水(shui)平下，LTC4155 的 88% ~ 94% 效率(lv)仍然可使熱預算限制(zhi)條件有(you)所放(fang)寬。LTC4155 的開關 PowerPath 拓撲結構可對從兩個(ge)輸(shu)(shu)入(ru)電(dian)源(yuan) (比(bi)如：墻上(shang)(shang)適(shi)配器(qi)(qi)和(he) USB 端口) 至(zhi)設備的可再(zai)充電(dian)鋰離子電(dian)池的功(gong)(gong)率(lv)輸(shu)(shu)送進行無(wu)縫(feng)管理，并(bing)在輸(shu)(shu)入(ru)功(gong)(gong)率(lv)有(you)限時優先向系統(tong)負載(zai)供(gong)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(ji)時(shi)接通”操作能力(li)，以(yi)確保(bao)在插(cha)入電(dian)(dian)源時(shi)可(ke)立即(ji)獲得系統功率，即(ji)使(shi)所采用的是一個(ge)失效的電(dian)(dian)池或深(shen)度放電(dian)(dian)的電(dian)(dian)池也(ye)不例(li)外。

　　在對電(dian)池進行(xing)高速充(chong)電(dian)時(shi)，監視(shi)電(dian)池的(de)安全性(xing)是很重要的(de)。LTC4155 將在電(dian)池溫(wen)(wen)度下(xia)降至(zhi) 0℃ 以下(xia)或上升至(zhi) 40℃ 以上 (由(you)一個外(wai)部負(fu)溫(wen)(wen)度系數 [NTC] 熱敏電(dian)阻(zu)負(fu)責測量) 時(shi)自動停止充(chong)電(dian)。除了(le)這種自主特性(xing)之(zhi)外(wai)，LTC4155 還提供了(le)一個 7 位擴展標度模數轉換器(qi) (ADC)，用(yong)于以大(da)約(yue) 1℃ 的(de)分辨率(lv)來(lai)監視(shi)電(dian)池的(de)溫(wen)(wen)度。結合(he) 4 種可用(yong)的(de)浮置電(dian)壓設定值和 15 種電(dian)池充(chong)電(dian)電(dian)流(liu)設定值，該 ADC 能(neng)夠用(yong)于建(jian)立基于電(dian)池溫(wen)(wen)度的(de)定制充(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(tai)和故障狀(zhuang)態(tai)。USB OTG (On-The-Go) 支(zhi)持(chi)能力可(ke)在未采(cai)用任何附加(jia)組件(jian)的(de)情況下(xia)提供一個返回 USB 端(duan)口的(de) 5V 電源。

　　LTC4155 的雙(shuang)輸(shu)入、優先級(ji)多(duo)路復用(yong)(yong)器可(ke)根據(ju)用(yong)(yong)戶定(ding)義(yi)的優先級(ji) (適(shi)配器輸(shu)入是默認的優先選(xuan)擇) 自主(zhu)選(xuan)擇最合適(shi)的輸(shu)入 (墻上適(shi)配器或 USB)。過(guo)壓(ya)(ya)保(bao)(bao)(bao)護 (OVP) 電路用(yong)(yong)于同時保(bao)(bao)(bao)護兩個輸(shu)入免遭(zao)因意外施加高(gao)電壓(ya)(ya)或反向電壓(ya)(ya)而造成(cheng)的損壞。LTC4155 的理想二(er)極管控制器可(ke)確保(bao)(bao)(bao)始終(zhong)能夠(gou)向 VOUT 提供足夠(gou)的功率，即使(shi)輸(shu)入功率不(bu)足或缺失也不(bu)例外。

　　對于(yu)諸如平板(ban)電(dian)腦或工業條(tiao)形碼掃(sao)描儀等許多便攜式(shi)(shi)應用而言，管理兩個輸入 (例如：USB和墻上適配器) 就(jiu)足夠了(le)。不過，便攜式(shi)(shi)設(she)備的(de)設(she)計人員(yuan)仍在繼續探(tan)尋能夠從任何可用電(dian)源來(lai)給電(dian)池充電(dian)的(de)方法。

　　多種輸入電源

　　諸多原因導(dao)致(zhi)用(yong)戶希望從多種輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。某(mou)些應(ying)用(yong)有可能需(xu)要(yao)脫離(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)網并指望由太陽能板(ban)來(lai)供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。其他的(de)(de)應(ying)用(yong)則希望擁(yong)有能夠從墻上(shang)適(shi)配器(qi)(qi)、汽車電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池或者高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)工業或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)進(jin)行(xing)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)便(bian)利。不管是什么(me)原因，這種要(yao)求都給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)系(xi)統施(shi)加了一個(ge)沉重的(de)(de)負擔(dan)。大(da)多數電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)均利用(yong)一種降(jiang)壓(ya)(ya)(ya)(ya) (開(kai)(kai)關或線(xian)性(xing)) 架構從一個(ge)高(gao)于(yu)(yu)最大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。早先的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)產(chan)品(pin)通常被限(xian)制于(yu)(yu)大(da)約(yue) 30V 的(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。此類局限(xian)性(xing)導(dao)致(zhi)設計人員無法考慮將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)信(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)作為可行(xing)的(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)，或者采用(yong)具有 42V 開(kai)(kai)路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)(de)太陽能板(ban)。在某(mou)些場合中，期望輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)范圍既(ji)會升至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)以(yi)上(shang)也(ye)會降(jiang)至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)以(yi)下。設計旨在應(ying)對上(shang)述難題的(de)(de)解(jie)決方案(an)通常需(xu)要(yao)整合高(gao)精度的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流檢測放大(da)器(qi)(qi)、ADC、用(yong)于(yu)(yu)控制充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)操作的(de)(de)微(wei)處(chu)理(li)器(qi)(qi)、高(gao)性(xing)能的(de)(de) DC/DC 轉換器(qi)(qi)以(yi)及理(li)想二極管或多路復用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。凌力爾(er)特公司推出(chu)了一款(kuan)更加優越(yue)的(de)(de)解(jie)決方案(an)。

　　功能強大且擁有無(wu)可比擬之(zhi)靈(ling)活(huo)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 PowerPathTM 控制功能。LTC4000 能夠(gou)驅動的(de)常用DC/DC 轉換器(qi)拓撲結構包括(kuo) (但(dan)不限于(yu)) 降壓(ya)(ya)、升壓(ya)(ya)、降壓(ya)(ya)-升壓(ya)(ya)、SEPIC 和(he)反激式(shi)。該器(qi)件提供了精準的(de)輸(shu)入(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(shu)入(ru)和(he)輸(shu)出電(dian)(dian)壓(ya)(ya)范(fan)圍(wei)內運作，因(yin)而與多種(zhong)不同(tong)的(de)輸(shu)入(ru)電(dian)(dian)壓(ya)(ya)電(dian)(dian)源、電(dian)(dian)池(chi)(chi)(chi)組尺寸和(he)化學組成相兼容。由于(yu)這款器(qi)件采(cai)用了通用型(xing)配(pei)置(zhi)，因(yin)此其典(dian)型(xing)應用范(fan)圍(wei)十分廣泛，包括(kuo)高功率電(dian)(dian)池(chi)(chi)(chi)充電(dian)(dian)器(qi)系統、高性(xing)能便攜式(shi)儀器(qi)、電(dian)(dian)池(chi)(chi)(chi)后備(bei)系統、配(pei)備(bei)電(dian)(dian)池(chi)(chi)(chi)的(de)工業(ye)設(she)備(bei)以及筆記本電(dian)(dian)腦 / 小型(xing)筆記本電(dian)(dian)腦等。

　　除(chu)了可(ke)支(zhi)持(chi)多種(zhong)不同的(de)(de) DC/DC 拓(tuo)撲結構(gou)之外(wai)，LTC4000 的(de)(de)高電(dian)(dian)(dian)壓(ya)能(neng)力還使(shi)其能(neng)夠(gou)利用(yong)幾(ji)乎任何輸(shu)(shu)入(ru)電(dian)(dian)(dian)源來(lai)形成功(gong)能(neng)強大的(de)(de)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)解(jie)決方案。為了確保(bao)來(lai)自這(zhe)些輸(shu)(shu)入(ru)的(de)(de)功(gong)率(lv)能(neng)輸(shu)(shu)送至合適的(de)(de)負載(zai)，LTC4000采用(yong)了一(yi)種(zhong)智能(neng) PowerPathTM 拓(tuo)撲結構(gou)，當輸(shu)(shu)入(ru)功(gong)率(lv)有限時，該拓(tuo)撲結構(gou)將(jiang)優(you)先向系統(tong)負載(zai)供電(dian)(dian)(dian)。LTC4000 通(tong)過控制外(wai)部 PFET 來(lai)提供低(di)損耗反向電(dian)(dian)(dian)流保(bao)護、電(dian)(dian)(dian)池(chi)的(de)(de)低(di)損耗充(chong)電(dian)(dian)(dian)和(he)(he)放電(dian)(dian)(dian)以及“即時接通(tong)型”操作，以確保(bao)在插入(ru)電(dian)(dian)(dian)源時可(ke)立即獲(huo)得系統(tong)功(gong)率(lv)，即使(shi)所采用(yong)的(de)(de)是一(yi)個(ge)失(shi)效的(de)(de)電(dian)(dian)(dian)池(chi)或(huo)深度放電(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)池(chi)也不例外(wai)。外(wai)部檢測(ce)電(dian)(dian)(dian)阻器可(ke)提供輸(shu)(shu)入(ru)電(dian)(dian)(dian)流和(he)(he)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流信息(xi)，從而使(shi)得 LTC4000 能(neng)夠(gou)與功(gong)率(lv)范圍(wei)從幾(ji)毫(hao)瓦(wa)到幾(ji)千瓦(wa)的(de)(de)轉換(huan)器一(yi)起使(shi)用(yong)。

　　LTC4000 的全功能電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)控制(zhi)器可(ke)對多種(zhong)電(dian)(dian)(dian)(dian)池化學(xue)組(zu)成進行充(chong)電(dian)(dian)(dian)(dian)，包括鋰離子電(dian)(dian)(dian)(dian)池 / 鋰聚合物電(dian)(dian)(dian)(dian)池 / 磷酸鐵鋰電(dian)(dian)(dian)(dian)池、密封鉛酸電(dian)(dian)(dian)(dian)池 (SLA) 和(he)鎳(nie)電(dian)(dian)(dian)(dian)池等。另外，電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)器還具有(you)高精(jing)度的電(dian)(dian)(dian)(dian)流(liu)檢測功能，可(ke)為高電(dian)(dian)(dian)(dian)流(liu)應用(yong)提(ti)供較低的檢測電(dian)(dian)(dian)(dian)壓。

　　新式便攜產品(pin)的(de)(de)設計(ji)師從(cong)事著(zhu)極(ji)富挑戰性的(de)(de)工作 ━━ 特別當其面對電(dian)(dian)(dian)源(yuan)時。客戶不斷地追逐需(xu)要消耗更多功(gong)率(lv)的(de)(de)功(gong)能(neng)，因(yin)而(er)必需(xu)使用更大的(de)(de)電(dian)(dian)(dian)池(chi)。與此同時，客戶還希(xi)望擁有從(cong)幾乎所(suo)有的(de)(de)可(ke)用電(dian)(dian)(dian)源(yuan)來給這(zhe)些(xie)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)的(de)(de)便利(li)(li)。雖然便攜式電(dian)(dian)(dian)源(yuan)的(de)(de)上述(shu)發展趨勢(shi)帶(dai)來了(le)設計(ji)難題，但(dan) LTC4155 和 LTC4000 則使設計(ji)工作大為(wei)簡化(hua)。在低電(dian)(dian)(dian)壓系統中，LTC4155 可(ke)高效提供(gong)高達 3.5A 的(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流，并具(ju)有諸多高性能(neng)特性。LTC4000 能(neng)夠利(li)(li)用幾乎任何(he)輸入來實現一款功(gong)能(neng)強大的(de)(de)充(chong)電(dian)(dian)(dian)解決方案(an)，且(qie)擁有無與倫比的(de)(de)性能(neng)及(ji)靈活性。