個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外，由電池(chi)提供的安全(quan)信號(hao)指(zhi)示電池(chi)是否(fou)呈(cheng)現在系統中和是否(fou)有熱引起的告(gao)警或在其(qi)他系統失(shi)效時是否(fou)電池(chi)失(shi)效。SBS顯著特點是安全(quan)、使用容易和兼容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太熱，則(ze)充電(dian)也將終(zhong)止。

　　SMBus 為系(xi)統和電(dian)(dian)源管(guan)理(li)這樣(yang)的(de)(de)(de)任務提(ti)供(gong)了一條控(kong)制總線，使用(yong)(yong) SMBus 的(de)(de)(de)系(xi)統，設(she)(she)(she)備(bei)(bei)之間(jian)發送和接(jie)收消息(xi)都是(shi)通(tong)過 SMBus，而(er)不是(shi)使用(yong)(yong)單獨的(de)(de)(de)控(kong)制線，這樣(yang)可(ke)以(yi)節省設(she)(she)(she)備(bei)(bei)的(de)(de)(de)管(guan)腳數(shu)。 　　使用(yong)(yong) SMBus，設(she)(she)(she)備(bei)(bei)還可(ke)以(yi)提(ti)供(gong)它(ta)(ta)的(de)(de)(de)生產(chan)信(xin)息(xi)，告訴(su)系(xi)統它(ta)(ta)的(de)(de)(de)型號，部(bu)件號等(deng)，針對(dui)掛起事件保存它(ta)(ta)的(de)(de)(de)狀態，報告不同類別(bie)的(de)(de)(de)錯誤，接(jie)收控(kong)制參數(shu)，并返回它(ta)(ta)的(de)(de)(de)狀態等(deng)。 　　SMBus器件存在(zai)現有7層(ceng)OSI網絡(luo)模型中的(de)(de)(de)前(qian)3層(ceng)，即(ji)物(wu)理(li)層(ceng)，數(shu)據(ju)鏈路層(ceng)和網絡(luo)層(ceng)。 　　SMBus最初的(de)(de)(de)目的(de)(de)(de)是(shi)為智(zhi)能電(dian)(dian)池(chi)，充電(dian)(dian)電(dian)(dian)池(chi)和與(yu)其他系(xi)統通(tong)信(xin)的(de)(de)(de)微控(kong)制器之間(jian)的(de)(de)(de)通(tong)信(xin)鏈路而(er)定義的(de)(de)(de)。SMBus也被用(yong)(yong)來連(lian)接(jie)各種(zhong)設(she)(she)(she)備(bei)(bei)，包括電(dian)(dian)源相關設(she)(she)(she)備(bei)(bei)，系(xi)統傳感器，EEPROM通(tong)訊(xun)設(she)(she)(she)備(bei)(bei)等(deng)等(deng)。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范的(de)全部安全要(yao)求，包括3分鐘定時器（保護SMBus通信換效(xiao)和喚(huan)醒模式期間鋰離(li)子電(dian)池過充電(dian)）。硬(ying)件可編(bian)程電(dian)注(zhu)和電(dian)壓限制(zhi)提供另外等級保護，這種(zhong)保護由(you)失效(xiao)軟件不可能改變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控(kong)制器(qi)(qi)，兩個控(kong)制充電(dian)器(qi)(qi)參(can)量的(de)10位DAC，一個熱敏電(dian)阻安全信號(hao)譯(yi)碼器(qi)(qi)，硬件電(dian)壓和電(dian)流限制譯(yi)碼器(qi)(qi)和一個SMBus控(kong)制器(qi)(qi)單元（見圖1）。

 智能(neng)電(dian)池(chi)或系統控制器(qi)通(tong)過SMBus接(jie)口(kou)命令對恒(heng)漢和恒(heng)壓(ya)限值進行編程。降壓(ya)變壓(ya)器(qi)用N-溝MOSFET做為開(kai)關(guan)，使成本降低、高(gao)效率工作。熱(re)敏電(dian)阻(zu)安(an)(an)全檢(jian)測電(dian)路檢(jian)測電(dian)池(chi)存(cun)在(zai)或確定電(dian)池(chi)溫度是(shi)否允許(xu)安(an)(an)全充電(dian)。

當通(tong)(tong)過(guo)SMBus傳輸接收恒(heng)流(liu)(liu)值(zhi)時，它被RILIMIT定標和限制到低(di)于(yu)編程值(zhi)。此修正值(zhi)編程電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)DAC，設置DC充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)DAC是10位△∑DAC，當希(xi)望充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)時，它從PROG引(yin)腳(jiao)吸收電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)（見圖2）。放(fang)大器(qi)PROG引(yin)腳(jiao)吸收電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)（見圖2）。放(fang)大器(qi)CAI感(gan)測RSENSE上(shang)的壓降并使此電(dian)(dian)(dian)(dian)(dian)壓跨接到RS2（200Ω）；流(liu)(liu)經RS2的電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)(tong)過(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)鏡(jing)像(xiang)做為PROG引(yin)腳(jiao)上(shang)的上(shang)接電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。流(liu)(liu)經RS2電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)與來自PROG引(yin)腳(jiao)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相匹配由CA2實現(xian)恒(heng)流(liu)(liu)工作。由于(yu)DAC輸出(chu)是一串脈沖，所以需要(yao)平(ping)滑(hua)電(dian)(dian)(dian)(dian)(dian)容器(qi)對脈沖濾波使其變為DC。

  LTC1759需(xu)(xu)要(yao)兩個電(dian)(dian)源(yuan)。PWM電(dian)(dian)路(lu)(lu)在墻(qiang)式適配(pei)器電(dian)(dian)源(yuan)斷開時(shi)(shi)直接通過Vcc引腳運行，邏輯(ji)(ji)功能(neng)運行與VDD電(dian)(dian)源(yuan)無關。PWM電(dian)(dian)路(lu)(lu)在去(qu)掉AC電(dian)(dian)源(yuan)時(shi)(shi)能(neng)進入40μA微功率停機模(mo)式，使(shi)邏輯(ji)(ji)和(he)SMBus工作(zuo)能(neng)保持運行，這是Intel ACPI標準所需(xu)(xu)要(yao)的。這種分離電(dian)(dian)源(yuan)也使(shi)邏輯(ji)(ji)和(he)SMBus能(neng)根據系統設計為員的需(xu)(xu)要(yao)運行在3V和(he)5V.為使(shi)LTC1759邏輯(ji)(ji)功耗(hao)最小，邏輯(ji)(ji)電(dian)(dian)流(liu)由時(shi)(shi)鐘電(dian)(dian)路(lu)(lu)激勵，時(shi)(shi)鐘電(dian)(dian)路(lu)(lu)當無動作(zuo)時(shi)(shi)停機并蘇醒服(fu)務(wu)于SMBus動作(zuo)或產生中斷。一旦(dan)請求服(fu)務(wu)，LTC1759便返回到休(xiu)眠。

　　當去掉AC電(dian)(dian)源或去掉電(dian)(dian)池(chi)時，通過(guo)CHGEN-SDB引腳(jiao)(jiao)組合發生PWM停(ting)機。LTC1759通過(guo)DCDIV通腳(jiao)(jiao)檢測AC損耗(hao)。閾值通常設置恰好低于墻式適(shi)配的最小有(you)效電(dian)(dian)壓。AC電(dian)(dian)源狀態通過(guo)SMBus可由系統(tong)讀(du)出。UV引腳(jiao)(jiao)只用于置PWM電(dian)(dian)路進入微功率(lv)停(ting)機狀態，它直接連到墻式適(shi)配器電(dian)(dian)源。

　　在設(she)計中電(dian)感器(qi)選擇(ze)不是關鍵，這是因為充電(dian)器(qi)的環路響應(ying)在意(yi)地設(she)置很慢。實際的低限值(zhi)為15μH左右，低值(zhi)電(dian)感器(qi)將產(chan)生(sheng)較高(gao)的紋波電(dian)流，在輸(shu)出(chu)需要較低ESR電(dian)容器(qi)。

　　輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的選擇對ESR（等效串(chuan)聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻）不(bu)(bu)(bu)是(shi)很(hen)苛(ke)刻(ke)，但必須(xu)處理(li)來(lai)自充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)的所有(you)紋波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。不(bu)(bu)(bu)用(yong)(yong)考(kao)慮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的紋波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，因為(wei)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)有(you)效阻抗遠(yuan)遠(yuan)大于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感器(qi)(qi)(qi)的ESR。很(hen)多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池組具有(you)內部(bu)串(chuan)聯(lian)保(bao)護MOSFET，這(zhe)提(ti)高了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池ESR。在(zai)多電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池配置中也有(you)與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池串(chuan)聯(lian)的功率路由(you)MOSFET，進一(yi)(yi)步增加了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池ESR。從(cong)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)觀點，輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)ESR可(ke)高達(da)1Ω，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)選擇范(fan)圍寬。當采(cai)用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子負載(zai)時，可(ke)能(neng)會(hui)發生某種不(bu)(bu)(bu)穩定(ding)性(xing)(xing)。增加300Ω電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)與PROG引腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)串(chuan)聯(lian)或(huo)在(zai)輸(shu)(shu)出(chu)置10μF電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)能(neng)改(gai)善穩定(ding)性(xing)(xing)。在(zai)輸(shu)(shu)出(chu)不(bu)(bu)(bu)需要用(yong)(yong)陶(tao)(tao)瓷(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)，因為(wei)在(zai)很(hen)輕負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)聲頻下(xia)開關變換(huan)器(qi)(qi)(qi)變得不(bu)(bu)(bu)連(lian)接和在(zai)下(xia)降周期開始(shi)時電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)會(hui)造成噪聲，應該(gai)采(cai)用(yong)(yong)鉭電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)選擇由(you)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)輸(shu)(shu)入(ru)紋波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)（一(yi)(yi)般(ban)為(wei)最大輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的1/2）決定(ding)。對于(yu)4A充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)(qi)建議用(yong)(yong)22μF（50V）陶(tao)(tao)瓷(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)，它一(yi)(yi)般(ban)可(ke)處理(li)2A紋波(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。

　　從電(dian)(dian)(dian)池(chi)(chi)到(dao)墻式(shi)適(shi)(shi)配器(qi)的(de)(de)電(dian)(dian)(dian)流保(bao)護由(you)P-溝MOSFET（Q1）提供(gong)。電(dian)(dian)(dian)壓(ya)比較器(qi)監控(kong)跨接(jie)在MOSFET上的(de)(de)電(dian)(dian)(dian)壓(ya)而且(qie)當(dang)墻式(shi)適(shi)(shi)配降到(dao)電(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)壓(ya)之上小(xiao)于(yu)200mV時(shi)關閉MOSFET。盡(jin)管價廉的(de)(de)二極管可用(yong)于(yu)替代以MOSFET，但(dan)MOSFET只增加100mV到(dao)0.4V低壓(ya)差工作(zuo)模式(shi)而不產生額外的(de)(de)熱量。在沒有電(dian)(dian)(dian)池(chi)(chi)起(qi)動(dong)時(shi)間，采(cai)用(yong)MOSFET附加二極管使墻式(shi)適(shi)(shi)配器(qi)電(dian)(dian)(dian)源能(neng)達到(dao)Vcc引腳并(bing)為PWM控(kong)制電(dian)(dian)(dian)路供(gong)電(dian)(dian)(dian)。

　　主(zhu)(zhu)要的(de)補償是(shi)(shi)d PROG引(yin)(yin)腳上進(jin)行；然(ran)而DAC脈沖濾波要求確定(ding)電(dian)容器(qi)有效值。脈沖紋波電(dian)流必(bi)須(xu)小平200mV或環(huan)路(lu)起(qi)伏(fu)（在(zai)輕載充電(dian)電(dian)流時出(chu)現(xian)的(de)環(huan)路(lu)不穩(wen)定(ding)性）。Vc引(yin)(yin)腳電(dian)容器(qi)的(de)主(zhu)(zhu)要功能(neng)是(shi)(shi)提供自啟(qi)動支(zhi)持。必(bi)須(xu)有一(yi)個1.5K電(dian)阻器(qi)與Vc引(yin)(yin)腳電(dian)容器(qi)串聯以能(neng)恰當停機(ji)。

　　從熱(re)觀(guan)點考慮，輸出電(dian)(dian)壓(ya)在電(dian)(dian)池(chi)(chi)溫(wen)度充(chong)電(dian)(dian)范圍(wei)內保持大約0.5%精(jing)度。精(jing)度越高，電(dian)(dian)流充(chong)電(dian)(dian)容量就(jiu)越大，而(er)更重要是在電(dian)(dian)池(chi)(chi)中與電(dian)(dian)壓(ya)基充(chong)電(dian)(dian)終端電(dian)(dian)路(lu)有關的問題就(jiu)會更少。

　　關(guan)于SMBus加速(su)泵，AC適(shi)配電(dian)流(liu)限(xian)制(zhi)，安(an)全(quan)(quan)信號感(gan)測，安(an)全(quan)(quan)電(dian)壓(ya)和(he)電(dian)流(liu)范圍設計等問(wen)題在此就不一一詳述(shu)。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。