單節鋰聚合物電池正在變(bian)成(cheng)便攜式和(he)超(chao)便攜式應用的(de)(de)主(zhu)要選擇。針對這(zhe)一(yi)終端市場而開發(fa)的(de)(de)AAT3681A是一(yi)個(ge)(ge)高性能(neng)的(de)(de)電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)，設計(ji)用于(yu)從一(yi)個(ge)(ge)外部(bu)(bu)電(dian)(dian)(dian)(dian)源以高達300mA的(de)(de)電(dian)(dian)(dian)(dian)流對單節鋰離子(zi)/聚(ju)合物電(dian)(dian)(dian)(dian)池(chi)(chi)進行(xing)(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。這(zhe)一(yi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流可(ke)使用一(yi)個(ge)(ge)外部(bu)(bu)電(dian)(dian)(dian)(dian)阻在15mA到300mA的(de)(de)很寬范圍內進行(xing)(xing)定(ding)制(zhi)。這(zhe)就(jiu)允許適配器(qi)/USB口在不同的(de)(de)應用中執行(xing)(xing)快(kuai)速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。它是一(yi)個(ge)(ge)獨立的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)解(jie)決方案，只需要一(yi)個(ge)(ge)外部(bu)(bu)元件(jian)就(jiu)可(ke)以實現全部(bu)(bu)功能(neng)。這(zhe)一(yi)器(qi)件(jian)可(ke)精確地為4.2V鋰離子(zi)/聚(ju)合物電(dian)(dian)(dian)(dian)池(chi)(chi)組調節電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓和(he)電(dian)(dian)(dian)(dian)流。

該器(qi)件(jian)的(de)額定工作溫(wen)度(du)范圍為-40℃到+85℃。在(zai)某(mou)一給定的(de)恒流充電(dian)水平下，當工作環(huan)境溫(wen)度(du)超出了該器(qi)件(jian)封裝的(de)功耗能(neng)力時，其充電(dian)控制將進入熱限制狀態(tai)。

該器件提供一個狀態(tai)監(jian)測輸出引腳，它可直接驅動一個外(wai)部(bu)LED來指示電池(chi)充電狀態(tai)。

器(qi)件結(jie)溫和充(chong)電狀(zhuang)態被充(chong)分監測，以防錯誤(wu)狀(zhuang)況發生(sheng)。

AAT3681A實現了(le)一個完(wan)整的保護(hu)系(xi)(xi)統。在過壓(ya)或過溫錯誤狀(zhuang)態(tai)發生時，該器(qi)件將自動關斷，以(yi)保護(hu)充(chong)電(dian)設備、控制系(xi)(xi)統和充(chong)電(dian)狀(zhuang)態(tai)下的電(dian)池。

充電操作

AAT3681A具有針對整(zheng)個電(dian)池充(chong)(chong)(chong)(chong)電(dian)周期(qi)的(de)四(si)種(zhong)基本充(chong)(chong)(chong)(chong)電(dian)模式：預充(chong)(chong)(chong)(chong)/涓流(liu)充(chong)(chong)(chong)(chong)電(dian)、恒(heng)流(liu)/快(kuai)速充(chong)(chong)(chong)(chong)電(dian)、恒(heng)壓充(chong)(chong)(chong)(chong)電(dian)和(he)充(chong)(chong)(chong)(chong)電(dian)終結。

電池預充

在充(chong)(chong)電(dian)(dian)(dian)(dian)開(kai)始(shi)前，為(wei)了確(que)保一(yi)個安全的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)環境，AAT3681A會檢查(cha)幾(ji)個條(tiao)件。輸(shu)入電(dian)(dian)(dian)(dian)源必須超過最小工作電(dian)(dian)(dian)(dian)壓(ya)或(huo)欠壓(ya)鎖定閾(yu)值，才(cai)能(neng)啟動(dong)充(chong)(chong)電(dian)(dian)(dian)(dian)順(shun)序。當這些條(tiao)件都已得到滿足且(qie)電(dian)(dian)(dian)(dian)池(chi)連接到BAT引(yin)腳，AAT3681A就檢查(cha)電(dian)(dian)(dian)(dian)池(chi)的(de)狀態。如果電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)低于預充(chong)(chong)電(dian)(dian)(dian)(dian)壓(ya)闌值，充(chong)(chong)電(dian)(dian)(dian)(dian)控制電(dian)(dian)(dian)(dian)路就開(kai)始(shi)對電(dian)(dian)(dian)(dian)池(chi)進行(xing)預充(chong)(chong)。電(dian)(dian)(dian)(dian)池(chi)預充(chong)(chong)涓(juan)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)是快速(su)充(chong)(chong)電(dian)(dian)(dian)(dian)恒流(liu)的(de)十分之一(yi)。

例如(ru)，如(ru)果(guo)可編(bian)程快速充(chong)(chong)電(dian)電(dian)流(liu)是300mA，那么(me)預(yu)充(chong)(chong)電(dian)流(liu)就是30mA。電(dian)池單元預(yu)充(chong)(chong)是針(zhen)對深度放電(dian)電(dian)池單元的一種安全預(yu)防措施，它(ta)也有助于限制導通(tong)晶(jing)體管上(shang)的功耗(hao)，因為此時該器件上(shang)的電(dian)壓(ya)差是最(zui)大的。恒流(liu)充(chong)(chong)電(dian)電(dian)池單元預(yu)充(chong)(chong)一直(zhi)持(chi)續到(dao)(dao)(dao)BAT引腳上(shang)的電(dian)壓(ya)超出預(yu)充(chong)(chong)電(dian)壓(ya)閾值(zhi)。到(dao)(dao)(dao)達此點(dian)后，該器件開(kai)始恒流(liu)充(chong)(chong)電(dian)階段。恒流(liu)充(chong)(chong)電(dian)幅值(zhi)由用戶通(tong)過設置電(dian)阻進行編(bian)程。AAT3681A一直(zhi)保持(chi)恒流(liu)充(chong)(chong)電(dian)模式，一直(zhi)到(dao)(dao)(dao)電(dian)池到(dao)(dao)(dao)達電(dian)壓(ya)調節點(dian)。

恒壓充電

在恒(heng)流(liu)快(kuai)速充電階(jie)段，當電池電壓到達輸出充電調節值時，系統就進入恒(heng)壓充電模式。

調(diao)節電(dian)(dian)(dian)壓水平(ping)在出廠時(shi)設置(zhi)為(wei)4.2V（?.5%）。恒壓模(mo)式下的充電(dian)(dian)(dian)電(dian)(dian)(dian)流掉下來，因(yin)為(wei)充電(dian)(dian)(dian)中的電(dian)(dian)(dian)池單元快到(dao)達其最大容(rong)量。充電(dian)(dian)(dian)周(zhou)期(qi)終結和再(zai)充電(dian)(dian)(dian)順序

在(zai)恒壓模(mo)式下，當充(chong)(chong)(chong)電(dian)電(dian)流掉到(dao)快速充(chong)(chong)(chong)電(dian)電(dian)流的(de)10%時(shi)，該器件就終(zhong)止充(chong)(chong)(chong)電(dian)，并進入(ru)睡眠狀態。充(chong)(chong)(chong)電(dian)器將保持睡眠狀態，直到(dao)電(dian)池電(dian)壓降到(dao)電(dian)池再充(chong)(chong)(chong)電(dian)壓閾(yu)值以下。

由于(yu)在(zai)睡眠狀態(tai)下(xia)消耗非常低的(de)電(dian)(dian)流，因此AAT3681A在(zai)不充電(dian)(dian)時(shi)可將電(dian)(dian)池泄(xie)露降到最低。這一特性(xing)對這樣一些應用來(lai)說特別有用，其輸入(ru)電(dian)(dian)源水平(ping)可能低于(yu)充電(dian)(dian)電(dian)(dian)池水平(ping)或欠(qian)壓(ya)鎖定水平(ping)。在(zai)這些情況下(xia)，當AAT3681A輸入(ru)電(dian)(dian)壓(ya)下(xia)降時(shi)，該(gai)器(qi)件將進入(ru)睡眠狀態(tai)，一旦輸入(ru)電(dian)(dian)源從錯(cuo)誤狀態(tai)下(xia)恢復(fu)(fu)過來(lai)，它再(zai)自動恢復(fu)(fu)充電(dian)(dian)。

散熱考慮

AAT3681A采用sC70JW-8封裝，它(ta)(ta)能夠(gou)散發高(gao)達(da)687mW的(de)功率，當它(ta)(ta)被正確地安裝在(zai)PCB板(ban)上時，并(bing)具有(you)最(zui)大160℃/W的(de)熱阻。在(zai)設計PCB和(he)安排該充(chong)電器IC與某一特定應(ying)用設計中的(de)其它(ta)(ta)散熱器件的(de)位(wei)置時，有(you)許(xu)多因素應(ying)當加以考慮。

保護電路；過壓保護

一個(ge)過壓(ya)(ya)(ya)事件(jian)的(de)(de)定義為：BAT引腳(jiao)上的(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)超過最大電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，并被設定在(zai)過壓(ya)(ya)(ya)保護閾值(zhi)。如(ru)果一個(ge)過壓(ya)(ya)(ya)事件(jian)發生，AAT3681A充(chong)電(dian)(dian)(dian)(dian)(dian)控制電(dian)(dian)(dian)(dian)(dian)路將關(guan)斷(duan)該器件(jian)，直到(dao)BAT引腳(jiao)上的(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)掉(diao)到(dao)OVP電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)水平以(yi)下。AAT3681A在(zai)過壓(ya)(ya)(ya)狀態消除后，再恢復正常的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)操作。

保護電路；過熱關斷

AAT3681A有一個熱(re)保護(hu)控制電(dian)路，一旦內部(bu)裸片溫(wen)度超過預置的熱(re)限制闌值，它就(jiu)關(guan)斷充電(dian)功能。一旦內部(bu)裸片溫(wen)度掉到(dao)熱(re)限制以下(xia)，就(jiu)自動(dong)恢復到(dao)以前的正常充電(dian)狀態。

充電電流的可編程性

用戶可借助(zhu)一個(ge)放在(zai)ISET引腳與地之間的設置(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)阻編(bian)程設定(ding)恒流(liu)充電(dian)(dian)(dian)(dian)(dian)(dian)水(shui)平。快速充電(dian)(dian)(dian)(dian)(dian)(dian)精度和預充涓(juan)流(liu)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，由(you)使用的設置(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)阻的容差(cha)決定(ding)。因此(ci)，推薦采(cai)用1%容差(cha)的金屬(shu)薄膜電(dian)(dian)(dian)(dian)(dian)(dian)阻。快速充電(dian)(dian)(dian)(dian)(dian)(dian)恒流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)范圍從15mA到(dao)300mA。