CN3059是一種對單節磷酸鐵鋰電池進行恒流、恒壓充電的充電器IC。用該IC組成的充電器主要特點：充電電流可由一外設電阻RISET設定，最大充電電流可達1A；輸入電壓4～6V，可采用USB接口或4.5～6V輸出電壓（輸出電流1000～1500mA）的AC/DC適配器供電；充電器電路簡單、外圍元器件少、成本低；對過放電（電池電壓＜2.0V）的電池有小電流預充電模式；內部有功率器理電路，若芯片的結溫超過115℃時能自動降低充電電流作過熱保護，使用戶可設置較大的充電電流，以提高充電效率；有兩個LED分別作充電狀態指示及充電結束指示；有輸入電壓過低（＜3.61V）時的輸出鎖存功能、自動再充電功能、電池溫度監測功能；采用小尺寸、散熱增強性的10引腳DFN封裝；充電溫度范圍0～45℃或0～65℃(由充電電池參數決定)。
CN3059是磷酸鐵鋰電池的專用充電器IC，但它還有一個獨特的特點：外設一個電阻RVSET，它可以增加恒壓充電的輸出電壓。利用這個獨特的特點，可以組成簡易的3節鎳氫電池充電器及4V鉛酸電池充電器或鋰離子電池充電器。
由CN3059組成的充電器適合充 0.5～4Ah的磷酸鐵鋰電池。其應用領域：礦燈、LED應急燈、警示燈；車模、船模、航模及電動玩具；在照相機中，用3.2V磷酸鐵鋰電池替代一次性3V鋰電池（型號為CR123A），其外廓尺寸相同；通信裝置；小型醫療儀器及野外測試儀器；小型電動工具等。另外，可采用CN3059組成充3節鎳氫電池及4V鉛酸電(dian)池的充電(dian)器等(deng)。

封裝(zhuang)、引腳排列及功能
CN3059采用散熱增強型10引腳小尺寸DFN封裝，其引腳排列如圖1所示，各引腳功能如表1所示。

圖(tu)(tu)1 CN3059引(yin)腳(jiao)圖(tu)(tu)

主要參數
CN3059的極限參數：各引腳的電壓范圍為-0.3～6.5V；BAT引腳與GND短路時間可連續；靜電擊穿電壓為2kV；最高結溫為150℃；焊接溫度為300℃（10s）。
CN3059的電(dian)(dian)(dian)(dian)(dian)(dian)氣參(can)數：電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)壓范圍為(wei)(wei)(wei)4～6V；靜(jing)態電(dian)(dian)(dian)(dian)(dian)(dian)流典型值(zhi)(zhi)為(wei)(wei)(wei)650μA；低壓鎖存(cun)電(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)(wei)VIN≤3.61V；預存(cun)電(dian)(dian)(dian)(dian)(dian)(dian)閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓是電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓小于(yu)2.05V；恒壓充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓3.6V；充電(dian)(dian)(dian)(dian)(dian)(dian)結(jie)束閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓（ISET端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓）為(wei)(wei)(wei)0.22V；睡眠(mian)模式閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)(wei)VIN－VBAT≤20mV；睡眠(mian)模式解除閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)(wei)VIN－VBAT≥50mV；TEMP端(duan)高溫(wen)閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)(wei)80%VIN，低溫(wen)閾(yu)(yu)值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)(wei)48% VIN。

典型應用電路
采用CN3059組成磷酸鐵鋰電池充電器電路與由CN3056組成的鋰離子充電器電路相比，前者有兩個突出的優點：①精確檢測充電電池的電壓，充電電池的終止充電電壓控制得更精確，使電池充的更滿；②采用在FB端與電池正極之間加接一個電阻RVSET，使充電器除能充磷酸鐵鋰電池外，也可簡單地組成充鉛酸電池及鎳氫電池，擴展了充電器功能。下面分別介紹這2種典型應用電路。
1、充磷酸鐵鋰電池電路
充電(dian)電(dian)池型號為(wei)26650，容量(liang)為(wei)2800mAH，采用1000mA恒流(liu)電(dian)充電(dian)（其(qi)充電(dian)率約0.36C），充電(dian)器(qi)電(dian)路如圖2所示。

                                                                                                              圖2 磷酸鐵鋰電(dian)池充電(dian)電(dian)路(lu)

充電器采用輸出直流電壓5V、輸出電流1500mA的AC/DC適配器作電源。用紅色LED作充電狀態指示燈，用綠色LED作充電結束指示燈。設定恒流充電電流ICH=1000mA，則RISET為：
RISET=1800V/1A=1.8kΩ （1）
CIN(10μF)及COUT(10μF)是為保證充電器工作穩定的輸入及輸出電容，可采用多層陶瓷電容器（MLCC）。
這里重點介紹精確電池電壓檢測電路。圖3是一般電池電壓檢測電路，圖4是精確電池電壓檢測電路。圖3中，BAT端外接充電電池，內接由R1、R2組成的電阻分壓器，其中間點為輸入誤差放大器，根據充電電池的實際電壓來對電池進行預充電、恒流充電及恒壓充電。若在恒流充電時的充電電流為ICH、BAT端的電壓為VBAT，電池的電壓為V’BAT。若BAT端到電池正極之間的金屬連接線的電阻為△R，則ICH電流從BAT端到電池正極間的電壓降VDROP =ICH×△R，則VBAT=ICH×△R+V’BAT (V’BAT＜VBAT）。充電電流越大，則VBAT與V’BAT的差值越大。輸入到誤差放大器的電壓是VBAT的分壓而不是V’BAT的分壓，因此產生電池實際電壓的檢測誤差。
再看圖(tu)4電(dian)路(lu)，BAT端向(xiang)電(dian)池(chi)充電(dian)。另外，由電(dian)池(chi)正極加一條連接到FB端，將電(dian)池(chi)電(dian)壓通過R1、R2分(fen)壓器后輸(shu)入誤差(cha)放大器。

圖3 一般電池電壓檢測(ce)電路(lu)

圖4 精確電(dian)(dian)池電(dian)(dian)壓檢測電(dian)(dian)路

粗看起來，FB端、電池正極端及BAT端是同電位的。但要注意的是從BAT端流到電池正極的電流是ICH，若連接線電阻為△R，其壓差VDROP=ICH×△R；而若從電池正極流入FB的電流是IFB，連接線電阻也為△R，則V’BAR－VFB的壓差為IFB×△R。因為ICH往往是0.xA～1A，而IFB≈3μA ，所以VBAT與V’BAT的壓差較大，而V’BAT與VFB之間的壓差甚小（VBAT＞V’BAT＞VFB），用VFB端反饋到誤差放大器的電壓與電池的實際電壓更接近，即檢測電池電壓更精確。這一種精確測量方法也稱為開爾文檢測法（KeLvin）。用這方法精確檢測電池電壓可使電池的終止充電電壓更精確，電池也沖的更滿。
2 、充4V鉛酸電池或3節鎳氫電池或鋰離子電池的電路
在FB端與(yu)電(dian)池(chi)正(zheng)極之間(jian)加一個(ge)RVSET電(dian)阻，可(ke)以調節恒壓充(chong)(chong)電(dian)的(de)電(dian)壓這一特點(dian)，則除充(chong)(chong)磷酸鐵鋰電(dian)池(chi)外，還可(ke)組成簡易4V鉛酸電(dian)池(chi)或3節鎳氫電(dian)池(chi)充(chong)(chong)電(dian)器，電(dian)路如圖5所示(shi)。

圖5 鉛酸電(dian)池或鎳氫(qing)電(dian)池充電(dian)器電(dian)路

設定的終止充電電壓Vbat與RVSET的關系為：
Vbat（V）=3.6（V）+3.04×10-6（A）×RVSET（Ω）            （2）
由于(yu)(yu)這種簡易充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)設定(ding)了終止充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓，所(suo)以(yi)在充(chong)(chong)(chong)電(dian)(dian)(dian)過(guo)程(cheng)不(bu)會產生過(guo)充(chong)(chong)(chong)電(dian)(dian)(dian)的(de)情況，即充(chong)(chong)(chong)電(dian)(dian)(dian)是安全(quan)的(de)。但由于(yu)(yu)不(bu)同(tong)種類的(de)電(dian)(dian)(dian)池(chi)(chi)有各自的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)程(cheng)式(shi)及終止充(chong)(chong)(chong)電(dian)(dian)(dian)的(de)檢測(ce)方法(fa)，因此用CN3059組成的(de)簡易充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)在充(chong)(chong)(chong)滿程(cheng)度上需要(yao)差一(yi)些。另外，在充(chong)(chong)(chong)3節(jie)鎳氫電(dian)(dian)(dian)池(chi)(chi)時，由于(yu)(yu)充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)沒有每(mei)節(jie)電(dian)(dian)(dian)池(chi)(chi)均壓充(chong)(chong)(chong)電(dian)(dian)(dian)的(de)電(dian)(dian)(dian)路，所(suo)充(chong)(chong)(chong)的(de)電(dian)(dian)(dian)池(chi)(chi)應(ying)是同(tong)一(yi)種型號、同(tong)一(yi)公(gong)司生產、同(tong)一(yi)組使用的(de)電(dian)(dian)(dian)池(chi)(chi)，否則會造成由于(yu)(yu)電(dian)(dian)(dian)池(chi)(chi)的(de)內阻(zu)不(bu)同(tong)而產生的(de)有的(de)電(dian)(dian)(dian)池(chi)(chi)未充(chong)(chong)(chong)滿，有的(de)電(dian)(dian)(dian)池(chi)(chi)已(yi)過(guo)充(chong)(chong)(chong)電(dian)(dian)(dian)的(de)情況。不(bu)同(tong)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)(chi)的(de)RVSET值如表2所(suo)示。

圖6 3.2V磷酸鐵鋰電池及3.6V鋰離子電池充電器電路