便攜式電(dian)(dian)源應(ying)用領域寬泛而多(duo)樣。產品(pin)涵蓋了從平均(jun)功(gong)耗僅幾 μW 的(de)(de)無線傳感器節點到采用好(hao)幾百瓦時電(dian)(dian)池(chi)(chi)組的(de)(de)車載式醫(yi)療或數(shu)據采集系統等眾多(duo)門類。然(ran)而，盡管品(pin)種繁多(duo)，但(dan)它們(men)卻呈現出了相對(dui)一致的(de)(de)發(fa)展趨(qu)勢 ━━ 設計(ji)人員不(bu)斷地(di)要(yao)求(qiu)其(qi)產品(pin)擁有(you)較(jiao)高的(de)(de)功(gong)率(lv)以支(zhi)持更多(duo)的(de)(de)功(gong)能，并指望(wang)能從任何(he)可用的(de)(de)電(dian)(dian)源來給電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)。第(di)一個趨(qu)勢要(yao)求(qiu)增加電(dian)(dian)池(chi)(chi)容量(liang)(liang)。不(bu)幸(xing)的(de)(de)是，用戶常常缺乏(fa)耐心，而且增加的(de)(de)電(dian)(dian)池(chi)(chi)容量(liang)(liang)必(bi)須要(yao)在合理的(de)(de)時間之內完成充(chong)電(dian)(dian)，這(zhe)就(jiu)必(bi)然(ran)導致充(chong)電(dian)(dian)電(dian)(dian)流的(de)(de)增大。第(di)二個趨(qu)勢則要(yao)求(qiu)電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)解決方案具有(you)巨大的(de)(de)靈活性。我們(men)將(jiang)對(dui)這(zhe)些問題逐個進(jin)行較(jiao)為詳細(xi)的(de)(de)探(tan)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(jiang)低(di)(di)電(dian)流需求(qiu)，但廉價的(de)(de)(de)(de) 5V 電(dian)源(yuan)管理 IC 的(de)(de)(de)(de)面市使(shi)得(de)越來越多的(de)(de)(de)(de)手(shou)持式設備轉而采用較低(di)(di)電(dian)壓(ya)架構。平(ping)板(ban)電(dian)腦(nao)很好地(di)體現了(le)這一點 ━━ 標準的(de)(de)(de)(de)平(ping)板(ban)電(dian)腦(nao)擁有豐富(fu)的(de)(de)(de)(de)功(gong)能(neng)(neng)以及非常(chang)大 (用于便(bian)攜式設備) 的(de)(de)(de)(de)屏幕。當采用一個(ge) 3.7V 電(dian)池來供電(dian)時，電(dian)池的(de)(de)(de)(de)容量(liang)必須達(da)到幾(ji)千mAh。為了(le)能(neng)(neng)夠在幾(ji)個(ge)小時之內(nei)完成此類電(dian)池的(de)(de)(de)(de)充(chong)電(dian)，需要(yao)幾(ji)千mA的(de)(de)(de)(de)充(chong)電(dian)電(dian)流。

　　然而(er)，消費(fei)者同樣(yang)希望能夠在沒有可(ke)用的大(da)(da)電(dian)流(liu)墻(qiang)(qiang)上適配(pei)器(qi)時從一個 USB 端(duan)口(kou)來為其高(gao)功率設備充(chong)電(dian)，這(zhe)種愿望并未因為上述(shu)的高(gao)充(chong)電(dian)電(dian)流(liu)而(er)被遏制。為了滿足這(zhe)些要求，在可(ke)以(yi)(yi)使(shi)用墻(qiang)(qiang)上適配(pei)器(qi)時，電(dian)池(chi)(chi)(chi)充(chong)電(dian)器(qi)必須要能夠以(yi)(yi)高(gao)電(dian)流(liu) (>2A) 進行充(chong)電(dian)，但仍然可(ke)以(yi)(yi)高(gao)效(xiao)地利用 USB 端(duan)口(kou)所提供的 2.5W 至 4.5W 功率。此外，產(chan)品還必需避免敏感的下游低(di)電(dian)壓組(zu)件(jian)遭受(shou)有可(ke)能造成損壞的過(guo)壓，將高(gao)電(dian)流(liu)從一個 USB 輸入、一個墻(qiang)(qiang)上適配(pei)器(qi)或電(dian)池(chi)(chi)(chi)無縫地引導至負載，并最(zui)大(da)(da)限度地降(jiang)低(di)功率損耗。與此同時，IC 必須安(an)全(quan)地管理(li)電(dian)池(chi)(chi)(chi)充(chong)電(dian)算法并監(jian)視關鍵的系統(tong)參數。

　　解決單節電池供電型便攜式產品的電源難題

　　盡管(guan)似乎無法(fa)找(zhao)到單(dan)個(ge) IC 來滿(man)足上(shang)(shang)述要(yao)求，但(dan)不(bu)妨考慮一(yi)下 LTC4155，這是一(yi)款(kuan)高(gao)(gao)功(gong)(gong)率、I2C 控制、高(gao)(gao)效(xiao)率 PowerPathTM管(guan)理器(qi)(qi)、理想二極(ji)管(guan)控制器(qi)(qi)和鋰離(li)(li)子(zi)電(dian)(dian)池(chi)充電(dian)(dian)器(qi)(qi)。該器(qi)(qi)件設(she)計(ji)用(yong)于從多種 5V 電(dian)(dian)源高(gao)(gao)效(xiao)地輸(shu)送高(gao)(gao)達 3A 的(de)(de)(de)電(dian)(dian)流(liu)，可(ke)為(wei)電(dian)(dian)池(chi)充電(dian)(dian)及系統用(yong)途提供(gong) 3.5A 以上(shang)(shang)的(de)(de)(de)電(dian)(dian)流(liu)。即使在這些(xie)高(gao)(gao)電(dian)(dian)流(liu)水平下，LTC4155 的(de)(de)(de) 88% ~ 94% 效(xiao)率仍然可(ke)使熱預算限(xian)制條件有所放寬。LTC4155 的(de)(de)(de)開關 PowerPath 拓撲結構可(ke)對從兩個(ge)輸(shu)入電(dian)(dian)源 (比如(ru)：墻上(shang)(shang)適配器(qi)(qi)和 USB 端(duan)口) 至(zhi)設(she)備的(de)(de)(de)可(ke)再充電(dian)(dian)鋰離(li)(li)子(zi)電(dian)(dian)池(chi)的(de)(de)(de)功(gong)(gong)率輸(shu)送進(jin)行(xing)無縫管(guan)理，并(bing)在輸(shu)入功(gong)(gong)率有限(xian)時優先向系統負載供(gong)電(dian)(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(bu)同，LTC4155 具(ju)有“即時接通”操作能(neng)力，以確保(bao)在插入電源時可立即獲得(de)系統功率，即使所采用的是一(yi)個失效的電池或深度(du)放電的電池也不(bu)例外。

　　在(zai)對(dui)電(dian)(dian)(dian)池(chi)(chi)(chi)進行高速充電(dian)(dian)(dian)時(shi)，監視電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)安(an)全性是很重要的(de)。LTC4155 將在(zai)電(dian)(dian)(dian)池(chi)(chi)(chi)溫(wen)度下降至 0℃ 以下或(huo)上升(sheng)至 40℃ 以上 (由一個(ge)(ge)外(wai)部負溫(wen)度系數(shu) [NTC] 熱敏電(dian)(dian)(dian)阻負責(ze)測量) 時(shi)自(zi)動停止充電(dian)(dian)(dian)。除了這種自(zi)主特性之(zhi)外(wai)，LTC4155 還提供了一個(ge)(ge) 7 位擴展(zhan)標度模數(shu)轉換器 (ADC)，用(yong)于以大(da)約(yue) 1℃ 的(de)分(fen)辨(bian)率(lv)來監視電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)溫(wen)度。結合 4 種可用(yong)的(de)浮置(zhi)電(dian)(dian)(dian)壓設定(ding)值和 15 種電(dian)(dian)(dian)池(chi)(chi)(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)流設定(ding)值，該 ADC 能夠用(yong)于建立基(ji)于電(dian)(dian)(dian)池(chi)(chi)(chi)溫(wen)度的(de)定(ding)制充電(dian)(dian)(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、充電器狀態(tai)和故障狀態(tai)。USB OTG (On-The-Go) 支(zhi)持能力可在未(wei)采用任何附加(jia)組件的情(qing)況下提供一個返回 USB 端口的 5V 電源。

　　LTC4155 的雙輸(shu)入(ru)、優先級多路(lu)(lu)復(fu)用器可根據用戶(hu)定義(yi)的優先級 (適(shi)配(pei)器輸(shu)入(ru)是默認的優先選(xuan)擇) 自主選(xuan)擇最合適(shi)的輸(shu)入(ru) (墻上(shang)適(shi)配(pei)器或 USB)。過壓(ya)保護 (OVP) 電路(lu)(lu)用于同時保護兩個(ge)輸(shu)入(ru)免遭(zao)因(yin)意外施加高電壓(ya)或反向(xiang)電壓(ya)而(er)造成的損壞。LTC4155 的理(li)想二極管控(kong)制器可確保始終能夠向(xiang) VOUT 提供足夠的功率(lv)，即使輸(shu)入(ru)功率(lv)不足或缺(que)失也不例外。

　　對于(yu)諸(zhu)如平(ping)板電(dian)(dian)腦或工業條形(xing)碼(ma)掃(sao)描(miao)儀等許多(duo)便攜(xie)式應用(yong)而(er)言，管(guan)理兩個輸入 (例如：USB和墻上適配器) 就足夠了(le)。不過，便攜(xie)式設(she)(she)備的(de)設(she)(she)計人(ren)員仍在繼續(xu)探尋(xun)能(neng)夠從任何(he)可用(yong)電(dian)(dian)源(yuan)來給電(dian)(dian)池(chi)充電(dian)(dian)的(de)方法。

　　多種輸入電源

　　諸多(duo)原因導(dao)(dao)致用(yong)戶希望(wang)(wang)從(cong)多(duo)種(zhong)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。某(mou)些(xie)應(ying)用(yong)有可(ke)能(neng)需要脫(tuo)離(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)網并(bing)指(zhi)望(wang)(wang)由太陽能(neng)板來(lai)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。其他的(de)(de)應(ying)用(yong)則(ze)希望(wang)(wang)擁有能(neng)夠從(cong)墻上(shang)適配器(qi)、汽車電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)或(huo)(huo)者高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)工業或(huo)(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)便利(li)。不管是什么原因，這(zhe)種(zhong)要求都給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)系(xi)統施(shi)加了一個沉(chen)重的(de)(de)負擔。大(da)多(duo)數電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)均利(li)用(yong)一種(zhong)降壓(ya) (開關(guan)或(huo)(huo)線性(xing)) 架構從(cong)一個高(gao)于最大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源來(lai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)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)產品通常(chang)被限制(zhi)于大(da)約(yue) 30V 的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。此類局(ju)限性(xing)導(dao)(dao)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)為可(ke)行的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，或(huo)(huo)者采用(yong)具有 42V 開路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)太陽能(neng)板。在(zai)某(mou)些(xie)場合中，期望(wang)(wang)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)范圍既(ji)會升(sheng)至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以上(shang)也會降至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以下。設計(ji)旨在(zai)應(ying)對上(shang)述難題(ti)的(de)(de)解決方(fang)案(an)通常(chang)需要整合高(gao)精度的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流檢測(ce)放大(da)器(qi)、ADC、用(yong)于控制(zhi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)操作(zuo)的(de)(de)微處理器(qi)、高(gao)性(xing)能(neng)的(de)(de) DC/DC 轉換器(qi)以及(ji)理想二極管或(huo)(huo)多(duo)路復用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。凌力爾(er)特公司推出了一款更(geng)加優(you)越的(de)(de)解決方(fang)案(an)。

　　功能強大且擁有(you)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(kong)制功能。LTC4000 能夠(gou)驅(qu)動的(de)常用(yong)DC/DC 轉(zhuan)換器拓(tuo)撲結構包括(kuo) (但不(bu)限于) 降壓、升壓、降壓-升壓、SEPIC 和(he)反(fan)激式。該器件提供了精準的(de)輸(shu)入電(dian)(dian)(dian)流(liu)和(he)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)調節，并可在一個(ge) 3V 至 60V 的(de)寬輸(shu)入和(he)輸(shu)出電(dian)(dian)(dian)壓范(fan)圍內運作(zuo)，因而(er)與(yu)多種不(bu)同的(de)輸(shu)入電(dian)(dian)(dian)壓電(dian)(dian)(dian)源、電(dian)(dian)(dian)池(chi)(chi)組尺(chi)寸和(he)化學組成(cheng)相兼容。由于這款器件采用(yong)了通用(yong)型(xing)(xing)配置，因此其典型(xing)(xing)應用(yong)范(fan)圍十分廣泛(fan)，包括(kuo)高功率電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)器系統、高性能便(bian)攜式儀器、電(dian)(dian)(dian)池(chi)(chi)后備(bei)系統、配備(bei)電(dian)(dian)(dian)池(chi)(chi)的(de)工業(ye)設備(bei)以及(ji)筆記(ji)本電(dian)(dian)(dian)腦 / 小(xiao)型(xing)(xing)筆記(ji)本電(dian)(dian)(dian)腦等(deng)。

　　除了可(ke)支持多種不(bu)同的(de) DC/DC 拓(tuo)撲(pu)結(jie)構之外，LTC4000 的(de)高電(dian)(dian)(dian)壓能(neng)(neng)力還(huan)使其(qi)能(neng)(neng)夠利用(yong)(yong)幾乎任何輸(shu)入(ru)電(dian)(dian)(dian)源(yuan)來(lai)形成功能(neng)(neng)強大的(de)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)解決方(fang)案(an)。為了確保來(lai)自這(zhe)些輸(shu)入(ru)的(de)功率(lv)(lv)能(neng)(neng)輸(shu)送至合適(shi)的(de)負(fu)載(zai)，LTC4000采(cai)用(yong)(yong)了一(yi)(yi)種智能(neng)(neng) PowerPathTM 拓(tuo)撲(pu)結(jie)構，當輸(shu)入(ru)功率(lv)(lv)有限時，該拓(tuo)撲(pu)結(jie)構將優(you)先(xian)向(xiang)系統負(fu)載(zai)供(gong)電(dian)(dian)(dian)。LTC4000 通過控(kong)制外部 PFET 來(lai)提供(gong)低損耗反向(xiang)電(dian)(dian)(dian)流保護、電(dian)(dian)(dian)池(chi)的(de)低損耗充(chong)電(dian)(dian)(dian)和(he)放電(dian)(dian)(dian)以及“即時接通型”操作(zuo)，以確保在插入(ru)電(dian)(dian)(dian)源(yuan)時可(ke)立即獲得系統功率(lv)(lv)，即使所采(cai)用(yong)(yong)的(de)是一(yi)(yi)個失效(xiao)的(de)電(dian)(dian)(dian)池(chi)或深度(du)放電(dian)(dian)(dian)的(de)電(dian)(dian)(dian)池(chi)也不(bu)例(li)外。外部檢測電(dian)(dian)(dian)阻器可(ke)提供(gong)輸(shu)入(ru)電(dian)(dian)(dian)流和(he)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流信(xin)息，從(cong)而(er)使得 LTC4000 能(neng)(neng)夠與功率(lv)(lv)范圍從(cong)幾毫瓦到幾千瓦的(de)轉換器一(yi)(yi)起使用(yong)(yong)。

　　LTC4000 的全功(gong)能電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)控制器可對多種電(dian)(dian)(dian)池(chi)化學組成進行充電(dian)(dian)(dian)，包括鋰離(li)子(zi)電(dian)(dian)(dian)池(chi) / 鋰聚合物(wu)電(dian)(dian)(dian)池(chi) / 磷酸鐵鋰電(dian)(dian)(dian)池(chi)、密封鉛(qian)酸電(dian)(dian)(dian)池(chi) (SLA) 和鎳電(dian)(dian)(dian)池(chi)等。另外，電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器還具有高精度的電(dian)(dian)(dian)流檢(jian)測(ce)功(gong)能，可為高電(dian)(dian)(dian)流應用提(ti)供較低的檢(jian)測(ce)電(dian)(dian)(dian)壓。

　　新(xin)式便(bian)(bian)攜產品的(de)(de)(de)(de)設(she)計師從(cong)事著極富挑(tiao)戰性(xing)(xing)的(de)(de)(de)(de)工(gong)作 ━━ 特別當其面對電源時(shi)。客戶(hu)不斷地追(zhui)逐需要消(xiao)耗更多(duo)功(gong)率的(de)(de)(de)(de)功(gong)能，因而必需使用更大的(de)(de)(de)(de)電池(chi)。與此(ci)同(tong)時(shi)，客戶(hu)還希望擁有(you)從(cong)幾乎所有(you)的(de)(de)(de)(de)可用電源來(lai)(lai)(lai)給這(zhe)些電池(chi)充電的(de)(de)(de)(de)便(bian)(bian)利。雖然(ran)便(bian)(bian)攜式電源的(de)(de)(de)(de)上述發展趨勢帶(dai)來(lai)(lai)(lai)了設(she)計難題(ti)，但 LTC4155 和 LTC4000 則使設(she)計工(gong)作大為簡化(hua)。在低電壓系統中，LTC4155 可高(gao)效提(ti)供高(gao)達 3.5A 的(de)(de)(de)(de)充電電流，并(bing)具(ju)有(you)諸多(duo)高(gao)性(xing)(xing)能特性(xing)(xing)。LTC4000 能夠利用幾乎任何輸入來(lai)(lai)(lai)實現一款功(gong)能強大的(de)(de)(de)(de)充電解決方案(an)，且擁有(you)無與倫(lun)比的(de)(de)(de)(de)性(xing)(xing)能及靈活(huo)性(xing)(xing)。