MAXIM MAX712

,
吟动
••••.•.•.•••••..••••.••••••.•••••.•...•.•..•.........•.........•..•...••...•.....•......•.•......••....
MAXIM
<<热门>> IC 数据手册之五十六
56-94.10
lVIAX712jlVIAX713
NicdfNiMH 电池快速充电控制器
-武汉力源单片机技术研究所
....................................................................................................................
一、概述
1. 1
-般说明
MAX'江2 和 MAX713 控制一个较最高电池电压至少高 1 伏的直流潭，对 Nicd 和 NiMH 电;也进行快
速充电，，--1 到 16 节的串联电池组可用 4C 的速率充电。电压斜率检测模致转换器、定时器和温度
窗口比较器决定充电的完成。 MA.."r712/MAX713 通过桓上 +5V 井联隐压器，由直流;军提供功率，并
且在不充电时，从电池吸取 5μA 的最大电流。当给电池的负载持续提供功率时低电位侧电流
敏感电阻允许对电池充电电流进行调整。
通过检测零电压斜率， MAX712 结束快速充电。而 MAX713 使用负电压斜率检测技术。两种器
件都为 16 脚 DIP 封装和 so 封装。需要的外部元件仅为一个外部功率晶体管、一个阻塞二极管、
三个电阻和三个电容。
对高功率充电要求 I MAX712jMAX713 可构成开关模式电池充电嚣，以减小功耗。
1. 2
应用
*电池供电的设备
膝上、笔记本和掌上计算机
手提式终端
峰窝电话(移动电话)
,
*便携式消费产品
便携式立体声录放机、 CD 布l
lé 绳电话
1. 3
管脚排列
TOPVIEW
百哥哥 I
s
一 DIPISO
图1
MAX712jMAX713 管拇排列图
.
191
‘.
,
• .1: :i. '.持点
.对 NiMH 或 Nicd 电池快速充电
·可对 1 到 16 节串联电池充电
拿钱性或开关模式功率控制
*当充电时，提供电池的负载
*从 C/3 到 4C 的速率快速充电:
*
C/16 涓流充电速率
*由快速充电自动切换到涓流充电
*电压斜率、'温度和定时器快速充电关断
*当不充电时，电池 5μA 的最大泄漏电流
*
+5V 并联调整器驱动外部逻辑
订购借患
1. 5
PART
TEMP. ftANGE
MAX112CPE
O'C to +70'C
MAX71 2C SE
MAX712Ci。
MAX712εPE
I
PIR-P ACKAGE
PART
T'EMP.RANGE
DIP
MAX713CPE
o.C to +70.C
O'C 10 + 70'C .
16 NarrowSO
MAX 7t3CSE
o'Cto +70'C
16 NarrowSO
O'C to +70'C
Dice'
MAX713C;。
o.C to +70.C
DicS"
-40 'C to +8S.C
16 Plastic D1P
MAX713EPE
4O'Cto +85.C
16 阴astic
MAX712ESE
-40'C to +85.C
16 NarrowSO
MAX713ESE
4O'Cto +8S'C
16 NarrowS。
MAX712MJE
毛S.C
16CERD1 P-
MAX713MJE
δS'C
16CεRDIP-
PIN-P ACKAGE
16 问 astic
to + 12S.C
,
to + 125.C
16 同âsticOIP
*与厂家协商器件技术参数
~
"与厂家联系，按 MIL-STD-883 处理·
典型工作电路
1. 6
优削
"
•
、存在与马挝、
图2
M.AX 712 /MAX713 典型工作电路图
二、特性
2.1
极限参鼓
V. JlJBATT-
,
F
...;.O.3V ,
+可V
192
,
DIP
BATT- 至~GND
士 1V
BATT... 至~BAT_T ，...
二一一没有提供功率时一一一一_.- ----…一一
...-.提供功率时-----…←
ι ←0___- 一
士 20 V.
-高于王 20V 或者二巨 2VX( 编程电池数)
DRY 到 GND 工也--飞二
二0.3V ，
FASTCHG到 BATT2:一、一一一二-一→-一
-0.3V , +1 2V
其它所有引脚到 GND-←一一'一一一
-0.3V , (V...+O. 3V)
V... 电流
100mA
DRV 电流♂午一一----…_.
100mA
→ REF 电流一一一?
+20V
10m A
连续功率损艳 (T A 叶 70'C)
塑料 DIP 封装 (+70'C 以上以 10. 53mW(C 递减)
842皿W
牵 so 封装机70'C 以上以 8.7mWrc 递减}
- 696mW '
陶瓷DIP 封装( +70'C 以上以 10.00mWrc 递减)
800mW
工作温度范围
岛iAX71-C-­
0'C-+70'C
MAX71一E-­
-40'C-+86'C
MAX71-MJE
-65 'C -+ 125 'C
贮存温度范围
-66 'C -+150'C
引脚温度(焊接， 10 秒)
+300 -C;::
~
强度超出上述极限参数可能导致器件的永久性损坏。这些仅仅是极限参数，并不意味着在
这些条件下或在任何其它超出技术规范规定的工作条件的情况下器件筒'自效地工作。延长在极
限参数条件下的工作时间可能影响器件的可靠性。
-2.2
电特性
句~
".
J
(Iv...""lOmA, TA=TIOQm. -TlOQax ，除非另有说明。参见典型工作电路。所有测量都是相对于
BATT- ，而不是相对于q.NDo)
CONOπ10NS
PtRAMETER
5mA<1vφ< 2OmA
V.如 ;\/oltage
:
•
、 τyp ,
MAX
UN
3 A-TT + Leal<age
V+ ..OV. BAτf... '" 1 内
SATT + Resistance wi世， PowerOn
PGMO.. PGMl .. BATT-. BATT..... 30V
‘
.-
唾←
ITIJ电
旨，
~
5
恤
矗
-拥‘
k!l
,0.5
C1 Capac:tan ce
~-J""
C2 Capac:tan ce
.
REFVoltage
'Unéervcltage lockout
αηA
~.
Percell
TLO. TEMP !nput Range
补1 1.
TLO Cffset Voltage (Note 2)
1.25
CN < TB:I P < 'ZV.
TEMP 、10阳ge
VUM叮Ac∞ rac:'I
rising
咱、-，
η;1 ，
TLO. TEMP. VUMIT Input
6ias Current
工
, 0.35
fnput Range.
将~1.
μF
:-:'5
1.96
< IREF < l mA
.I
snA < =lOPRG
V < aknA.
PGMO = ?GMl .. V+
^-
I~有R
ITs l
v
_5" 一
Iv. (No te 1)
ξxt9mal VUMIT
MIN-
币 4.5 气， .…A 卢;二--'喃 5.5
与
-气三
nF
--:::-:_-
2.04
V
~~'
0.5
V
，>，二丁-
之5
V
o
2
V
-10.
10
mV
1
j1Ä
组
mV
…,
、 -晶田
.1
(也 "晶苟， .哑严，
-30
•
忖二:气
.•
193
,
，再
续上表
CONCπlONS
MIN
TYP
1.6
1.55
1.7
V
225
250
275
mV
PGM3 疆、'1+
1. S
3.9
7.0
PGM3 =- ooen
4.5
7.8
12.0
PARAMETER
字~
IntemaJ Cðll Vcl 恒geümit
Fast毛h缸geVSENSE
1 VUM !T =V+
'.
Trickl e-C:"I arge VSENSE
PGM3 = REF
I
PGM3=- BA了T-
12.0
15.6
20.0
26.0
31.3
38.0
.
mV
-2.5
V(Nooittaag3H) lope sem后Vlty
o
MAX712
percell
TimerAc∞racy
.电，、5
lS
Baiwttdeeryr-Avoccltaugrz e to ceti-Voltage
Divider Accuracy
-1.5
1.5
%
,
I Vc阳 =10V
OAV SJnk Current
FASiC衬G
UNπ's
MAX
Low Current
VFÄSTC l-1 G = Q.4V
FASTCHG High Current
VFASfCHG = 10V
扭
rnA
2
mA
1.4
AJD IncutR甜伊
%
JO
μA
1.9
v
Z
Ti攻击f
京et生
t雪 'aah汪
L1531fzL曹
位
f
T古
E
a--2·r'
'
4dj
、v
户丘吉F笔
注 1: V+端给 MAXπ2月{AX'丸3 提供功率。因为 V:... 并联调整到+5V， R1 必;#j足梅小以允许至少 5mA的
电流进入 V+ 端。
注 2:
THI 和 TLO 比较器的偏移电压以 TEMP 为参考 a
注 3:
t A 为 A/D 采样的间隔时间(见表 3) 。
典型工作特性
2.3
..
(T A =+25'C ，除非另有说明)
,
20
20
10
10
{ES
莲Z
。
{咀
)雹
z
主白
〈咀
在飞
-fi-F
<
M
。
-10
-120
1蚀∞k
1M
10M
fRfOUENCY !Hzl
图 3( a) 电流敏感放大吉普频率响应
(使用 15pF 电容)
-20
10
1∞
:k
~lÆNCY(~
图 3(b) 电流敏感的大梧频率响应
(使用 10nF 哇容)
,
194
、-，
~
气司工富立
ι..
-
-~
s.a
1∞
__
缸
- - - - - --
~
~-→.-凹
吉 -f
雪p
SUMZ主
A主运
1. 5
:5
1.4
Jl主
ε11
1.0
<S~
5.且
丘4
au
唁ε
u
量
E司4J
-34S
‘
υ，
22g
当
.二注:白
I .l
W
巳3
IS :;:;
主
:巳接.，4.4 口 '1
"'t
::::s
主
A.c.
:0
9
5 至
:~~~j~斗 ;Ji二2
』
4.0
III
1~
1.97
v
图 3( c)
.1.到LØ1
2.Øl咱 m
a
lQ
o
飞三，­
岱20
3口创
50
m
8l
CURß四T INTO V+ P!N (mAl
明孔TNiE ()f CC PII (v)、 J
图 3(dL 并联稳压器电压随电流图 3(e) ALPHA 热敏电阻
电流误差放大器跨导
手 J的变化特性、-
飞、
(型号:
3AI002)
与电池温度的关系
"句-
~
..→--.一千
1!刃
s;-
p
革运至1.45
主呈
3主 3
...
1.40
':; <..>
S·山
)主写SLZFdzu
40
写到三
1.&l
40
<..>
1.40
2s
。
II
&l
。
90
α-w程古眨('-'INUTES)
30
&l
CHNIGE TIME (1.4刷UTES)
. 0
90
50ω150
CHAAGEπME (MIH
UTES1
图 3(η MAX713 在 C 速率时对图 3(g) MAX713 在 C 速率时对 NiMH 图 3(h)MAXπ3 在 C/2速率时
电池充电特性
Nicd 电池充电特性
对 Nicd 电池充电特性.
"
、A
1.65
1 且5
35;;-ε
艺 1 .50
二:>
316
g
...
也"
....
-'ιa
23
也3
也J
7
1.40
25
E
50
∞
150
CliNa TIJ.IE (MN1TES)
王
苟言 :1到
3531m
二
<=:-
当罢王 1.55
当坦 1 .55
当
剑
ιa
t....
-u去
·--2
运主』 448
40
1 回
也~
勾当羽唱"
抱
a
5
10
.~
g
20
15
-'1.45
5
10
15
20
0协阳王T1ME (MlNU1t5l
0协RGé TIME (MIHUl5)
图 3(i)MAXπ3 在 C/2 速率时对图 3(J)MAX713 对充满电的 NiMH 图 3(k)MAX713 对充满电 NiMH
NiMH 电池充电特性
.i 电池的克电特性
今…一
电池的充电特性
τ.
嘻，.
.~
‘
..
195
,
霄卸说明
2.4
τ』
二名
-引脚
称
置最大电;也电压。如果 VL 1 M.门连接到 L 端，电;也端电压 lBATT.-BATTJ
VL IMIT
户口斗，
将不能超过l. 65VX (电池的个数); -否则， 电;也端
sv电.除压非将连不接能到
超过
V Ll Y 门 X( 电池的个数)。飞不允许 YLI14 门超过 +2. SV. ~~F~~!~ v. 端。
-- - -
-
自B
:r:1J
矗-、
3. 4
电 - - .~"":i占
BAH.:"--
电池的正端 ι
PGMO
PGM. O 和 PGMI 决或定者串使
联充电电池的数目。通过连接 PGYO ~.-PGW1 到飞、
lE F 或 BA TT - l _ ~W f!: PGMO 、_ PGMI 开路(见表 2) .决定 i 到"节的电池;
二 PGM 1.---
,
-
目。
-啕'
THI
过温度比较器的跳转点。如果 TE14P 端电压上升超过 THI 端电压，快速
TLO
温度不量电够压比时较上器电的， 跳转点。如果刘AX7121MAX7 门在 TEYP 端上电压小于
TLO 端
, 快速充电充被禁器止的，并最且小直工到作 TE M. P 上升到高于 TLO 时
充电结束。
才开始。 TLO 必须被置为低于电
11
FASTCHG
揭极开路快速充电状态当快输速出充端! 。当 MAX712/ M. AXì 门对电池快速充电时，
FASTCHG 吸入电流。当
吸入电流。
电结束并且涓流充电开始， FASTCH~停止
PGM. 2 使和 PGM. 3 置允许快速充电的最大时间。通过连接到 L 、 REF出或时3A间
TT。
或者
PGMl 、 PGM3 开路(见表 3) .可置 J 3 分钟到 164 分钟的输
PGM3 还决定快速充电到涓流充电的电流比例。
cc
恒定电流调整环路补偿输入端
BATL
电池的负端
'
系统地。在 BATL 和 GND 之间接一个电阻，用于监槐进入电池的电流。
DRV
驱动外部 PNP 电流源的电流吸入端。
15
Y.
并联稳压器。 L 端的电压调整到相对于 BATL 端的.. 5V.
驱动 MAX7121YAX713o
16
.-UF
14
.
由热敏电阻得到的眩赖温度的感应电压输入端。
.GND
13
"
TE M.P
PGM. 2
PG143
9. I 0
温度。
•
2. 0V 基在源输出。提供
并且分流电流
I I! A 输出。
三、应用步骤
MAX;12lMAX713 使用起来很简单。完整的电池充电器电路可按以下步骤设计 a
1.根据电池使用说明推荐的最大充电电流，决定在你的应用中特定电池充电结束的方法。
表 1 提供了一般的指南。
表1
充电速率
>2C
2C 到 C I2
<C I2
快速充电的结束方法
NiMH 电池
6V/6t 和温度 IMAX 712 或 MAX713)
6V/6t 和/或者温度 (14AX7 t 2 或 MAX7
6V/6t 和/或者温度 (14AX712)
Ni e d 电池
t 3)
6vt6t 和温度 tMAX713)
6V/6t 和/威者温度 (MAXìI3)
6V/6t 和/威者温度 (MAX113)
2. 决定充电速率。 C/3 速率对电池充电大约需三小时。以这个速率充电时，要求的电流
(mA) 可通过下式计算
，
R
IFAs-r=(电;也容量 mAh) /(充电时间的个时数)
‘
196
.
,
ι
付
，
‘呵
对于不同的电池 i 充电效率可低于 30%~二所以 C/3 快速充电可进行 3 小时 45 分钟。这不代表
MAX712/MAX713 的效率， 72 它反映 7 电能量转换为电池的化学能量的姓率。
3. 选择外部 DC 功率濡(例如:插头状的 AC-DC 转换器。它的最小输出电压(包括纹波)必须
高于远 V._:- 并且至少比量重大电池电压高 I 伏 4
4. 用以下公式计算是坏情况下功率 PNP 管和二极管(典型工作电路中 Q1 和 Dl}的功链，以瓦
....
为单位二二;、IC:1ιi '
"二:P D~p~-~( 负载最小电池电压条件下是大 AC-DC 转换器电 ffi) X (-充电电流)
5_ 如果在你的应用中超过了最大功起;如果你的电池组超过了 11 节电池仁或者允许电
流超过了600mA，查阅"详细说明"一节。另外，应用典型工作电路，并计算 R1 和 RSENSE 的电
阻值。
6. 按以下方程选择 R1 ，单位为 kQo
R1=( 插头状 AC-DC 转换器的最小电压 -5V)j5mA
7.
用以下公式选择 RSENSË:
~2
.ð833
RSENSE=O.25V/ (I FAST)
1
巧s-
0_(
气 I扩。俨 0，>
A
2F..f之
8. 查阅表 2 和表 3 ，决定管脚连接。例如:以 C/2 的速率快速充电，置输出时间为1. 5X 或 2
×充电周期之间，即 3--4 小时之间。
表2
电池数
1
电池数量的搞程
表3
PGM1 连接
PGMO 连接
V+
V+
事
(min)
open
V+
3
REF
V+
2
V+
33
33
4s
(sec) (tA)
21
21 _
21
21
42
42
22
BATT-
5
v+
open
6
open
open
7
REF
open
8
9
10
BATT-
4s
66
66
open
V+
REF
open
REF
11
REF
REF
12
BATT-
REF
13
V+
BATT-
14
open
BATT-
15
REF
BATTJ-
16
BATT-
BATT-
cSLhIi。ammpiet-
TIm回ut SI翻
ntneprviianig
2
4
革大充电时间的编程
Disabled
Enabted
Disabled
Enabled
DiSabled
42
由
84
84
αsa创ed
V+
BATTopen
. AEF
-
V+
RE严
BATTooen
REF
-8、abled
。isabl甜|
8A廿.
V+
Enabled
8ATT-
BATT-
Disabled
Enabled
I
V+
AEF' I
AEF
REF
8ATT8ATT-
…Enabled .
84
132
168
180
180 - --188
188
264
264. I … t88 -
V+
open
open
open
open
后1abled
84. 一
132
乏 V+
Disabled
9ö
open
AEF
V+
|岛也i时
42
PGM2
PGM3
Connec刽。" Conn缸刽。"
Di础刷
V+
8ATT。 pen
REF
.，乌龟‘
飞、、电
-，.-....，._"""一…~.、一………、 .....y.二
自-
"-""、俗一
管-，白、也 k...._.
...
...‘
.
_、吨 9
~
"也.龟四
.
~
-
.
1
、_...
197
,
.
囚、详细说明
通过迫使恒定电流混入电 i毡 I MAXπ.2JrvL-\X713对 NiMH 或 Nicd 电池快迫充电。MAX'π2/MAX713
，总是处于两种状态之一:快速充电状态或者涓流充电状态。在快速充电跑间，电流较大。一旦
检测到电池己充满电，电流减小到涓流充电。器件通过监视三个变量来夜定电池是否充满电:
电压斜率、:二电池温度和充电时间。
MAX712jM AX713 的方框图如图 4 所示。定时器、电压斜率撞测、温度比较器用于决定充满电
状态。电压和电流调节器控制输出电压和电流，并且感知电池的存在 n
在加上电海以前，电池已接好的典型充电情况如图 5 所示。在时间 1 ， MAX'π2{M AX713 从电
池吸取微不足道的能量。当电源加到民因端{时间 2) ，上电复位电路(见困 4 中 POW且:.R-ON-RF.S囚'
信号)保持 MAX712fMAXπ3 处于涓流充电状态。一旦 POWER-ON-RESEí'变为高，只要电池电压高于
欠压锁定 (UVLO) 电压(每节电池 0.4吟，器件进入快速充电状态(时间 3) 。只有(电池电压) /(电
池数量)大于 0.4V 时，快速充电才开始。
只要电池电压斜率变为负，快速充电立即结束，并且 MAX712/M AX713 转换到涓流充电状态
(时间 4) 。当电源关闭(时间 5) 时，器件从电池吸取很微小的电流。
使用温度憧查是否充满电的典型充电情况如图 6 所示。图中所示情况，是电池很冷的快速
充电情况(例如:外部环境很冷造成的)。在时间 2 期间 ， MAX712/MAX713 保持涓流充电。一旦达
到安全温度(时间 3 )，开始进行快速充电。当电池温度超过 THI 端所置的极限温度， MAX712
/MAX713 回到涓流充电状态(时间 4) 。
M AX712/MAX713 可通过电压斜率检测电池是否充满电，也可通过温度憧测电池是否充满电。
在 MAX712jMAX713 已经上电的情况下，插入电池的充电情况如图 7 所示。在时间 1 匍间，充
电器输出电压调整为电池的数量乘以 VLIMIT 0 MAX712f.岛1AX713 处于涓 t庵先电状态。依据电池的
插入(时间匀， MAX712甩在AXπ3 检测流入电池中的电流，并且进入到快迫充电状态。一旦检测到
电池充满电器件转入涓流充电状态(时间 3) 。如果电池已经拿开(时间 4) ， MAX712{MAÏ113 保
持涓流充电状态.输出电压再次象时间 1 期间一样进行调整。
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电池插入时的典型充电情况
MAX712/MAX713 的电源
在无ACLDC转换器电压的条件下. MAX明MAX713不工作i 从电池吸取量大为5队的电流。
二极管 D1( 旦典型工作电路)防止由选入 DRV 端的导通电流提供的对Q1集电极偏重。当 Aι.DC转换
器电源被连接上，通过 R1 对 Cl 充电。一旦α充电达到 5V，!自部并联调堕?牛入电流.将 V+调整到
+5Va 并且快速充电开始进行。
如果 DCIN 超过 20V，在 DRV 端加接串联共射共基三极管如图 8所示，以防止 DRV端电压超过
极限参数。
一 γ-
一
选择R1 的阻值，使得在最小的 DCIN 电压时.流过1悍的奥革为 ~A( 见?应用步骤"一节中
的第 6 步)。最大 DC IN 电压和是小 DC IN 电压的差决EEZMA乒712lMAX713 的功耗。
进入 V+ 的最大电流..(最大 DC IN 电压 :-~~>.~tL 二:
由于并联稳压器引起的功耗 =5￥X( 进入飞的最太电事〉i￡吕"7 ζ二
DRV 端的吸入电流也引起功艳。不要让息的要彗理过34革限~J!~:~中~1~ 出的J 参致。
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EιrJ
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表4
MAX712/M AX713 充电状态转换表+
POWER
。N_RES~
IN_
UNDER_
VOLTAGE REGULATl ON
x
x
COLD
同时
x
x
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x
No
change
o
No
o
X'
T
1
T
x
- t
x
x
T
o
o
O
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o
N。
o
o
o
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o
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ι
o
i
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x
x
o
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1
T
o
x
Set Trickfe
1
o
?
X ! SetTrickle
lnhibited
、
..
+仅存在两种状态:快速充电状态和涓流充电状态。
*无论其f逻辑垒的状态如何， HδT上的任何下降沿、暂停，或者电底斜率捡测，接定涓流克
电。
"如果在上电时电池温度较低， Cδtu端上的第一个上升沿将触发快速充电，当然第二个上升沿
将无效。
4.2
快速充电
'在以下条件中之一 l MAX712 /M AX713 进入快速充电状态:
。)依据使用的电前进行电庄电流检测(例如: GND 电压低于 BATr-电压)， ，因MP 高于 Tω ，
并且电池电压高于 UVLO 电压。
(2) 依据接入的电池 TEMP 道于 TLO，低于 THI，并且电池电压高于 UVL0.电压。
Rs&NBE决定流入到电池中的快速充电电流。在快速充电时， BATr-fnGND 墙之间的电压差被
200
要
.,
}三1 聋:;~苓悲喜必
在 250mV 。如果电压差小于250mV ， DRV 端增加吸入电流，如果电压差大于250mV ，则减也吸
入电施。.
快速充电电流 (1"AST)-C.25V/R S B: NS B:
4.3
渭流充电
选择 C/2 、 C 、 2C 或化的快速充电电流 (I FAST ) 保证 C/16 的涓流充电电流。其它速率的快速
充电也可使用，但涓流充电电流将不是准确的 C/160
:;..号
MâX7Î.2/MAX713 通过增加电流放大器的增益(见图的，调整ReB:N81G上电压(见电特性表中涓
流充电 VS B: NS B:)，在内部决定了涓流充电电流。
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PGM3
电流和电压稳压器
由 PGM3 决定涓流充电电流的大小
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4.4
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v
决定参数:
使用 MAX713
民MO=V啊 PG1vU=开路. PG1f2,:BA'IT-. PGM3=BA'IT-, ~晒g=L5Q( 快速充电电流IFA田·
..167mA) , R1={ 6V -5V) /5皿A=200Q
因为 PGM3=BATr-， RsENSB:上电压在涓流充电期间将被调整到乱3mV. 电混得为 20.7皿A。此
涓流实际为 C/25 ，而不是 C/16o
4.5
对 NiMH 电池进一步浦小涓流充电电流
使用图 10 所示电路，可捋涓流充电电流减小到小子 C/16 。在涓流充电期间因为 Q2 导通，
一些电流将绕过电池被分流。按下式选择 R7 的值:
R7-{V BATT...O_4V) !(ITRICKL B: -IsATT)
这里
V BATT = 充电时的电池电压
ITRICKL B:"， MAX712/MAX713 涓流充电电流值
'
I sATT = 要求的电池充电电流
γ
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4.6
对 NiMH 电池减小涓流
调节环路
调节环路控制 BAIT... 和 BAIT- 墙之间的输出电压，和自 BA1T-与 GND 之间的电压导致的流经电
池的电流。当输出电压超过电池的数目乘以 VLIMIT ，或者电池电流超过编程的充电电流， DRV
端的吸入电流减小。这个环路提供以下功能 z
(1) 当充电器已经上电，电池可以移走 z 而不需要中断负载上电流。
(2) 如果负载象典型 ZL作电路那样连接，电池电流被调节，而不考虑负载电流{提供输入
功率的源可向两者提供电漂)。
202
,
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4.7
电压环路!
ι
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电压环路置 BATT+ 和 BATT- 竭之间的最大输出电庄。如果 VLIMIT 被置得小于 !!.5V，则:
最大 BATT+ 电压(以 BATT- 为参考点 )-VLIMITX( 由 PGMO ， PGM1 决定的电池数目)。
;如马果 VILIMIT 连接到 γ;远(跑芋于毛-'
-
fg天 BATT~~电EiaE丘于二五气参考J品马;白?文(由 PGMO ， PGM1 决定的电池数自)。
把电池移开， MAX712/-~AX引3 不提供恒定电施，它调整 BATT+ 到.以上决定的最大电压。
法载运波器捻-cf毡寿路稳定q 仅在学少-负电站 ;'-MAX712/MAX713 对负载提吻气 :彭
的情况下，需要较大的滤波器电容。在这种情况下， ".C3 可置为
C3( 法拉)啊 XILo~D)/(VoUTXBWYRd
这里 BWY R. L"" 环路带宽，单位为 Hzo (推荐值为 10 ，
d ~l工等问泻仄/仰
C\1Y ~-Yl 町、
U.
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毒
扣
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C3>10μF
ILo ....-i:，;;;'先部负载电流单位为安培
Voirr= 编程输出电压 (VLIMITX 电池的数目)
4.8
电流环路、
平二
电流环路如图 g 所示二字为保证环路稳定，必须使电流调整环路的带宽 (BWCRd 低于晶体管
Q1 的极点频率 (f ~)。选择 C2 决定 BWCRLO
BW CRL(Hz) 吁国 IC 2
C :.z的单位为法拉 I
g_=0.0018 西门子。
PNP 晶体管 Q1 的极点频率，可通过假定单极点电流增益响应来得到。对于使用的特定晶体
管 Q1 ，其 f-r和 f~ 在数据手册中都有详细说明。
f~(Hz) ，.. fT/ßO ，
f T 单位为 Hz ，
电流调节环路的稳定条件 t
ß 0= 直流电流增益。~
BWCRL<f
fS
在 DRV端产生的电流和电压，会引起 MAX712!MAX713 的础。不自吕允许功耗超过极限锁。
托
!;
通过使用图 8 中所示的共射共基连接，可减小 DRV 端的功耗。~.
DRV 墙吸入电流引起的功耗刊进入到 DRV 端的电流) X(DRV 端上电压)
4.9
町
判断电压斜率关黯缺速充电
M:AX712t1víAX713 模数转换器具有 2.5mV 的分辨率。在 t A 期间(见表 3) ，它存贮电池电压。在
舍两个 t A 期间，得到在 t A 期间的不同电压，从而决定电池电压随时间变化的斜率。每次 A/D转换
被平均，超过 5mS 滤除一次输出噪声。因为电流调节环路使电池电流值定(甚至在外部负载变化
的条件下)，转换结果较精确。
当转换的结果等于和小于它的原有值 J MAX7í2 结束快速充电。当转换结果至少小于它原有
结果值 2.5mV 时
4.10
MAX713 才结束快速充电。这是 MAX712 和 MAX713 之间仅有的不同。
温度判断关断快速充电
在图l1 (a) 中示出了 MAX712βfAX713 使用一个负温度系致的热敏电阻，来撞测电池超温条件
和温度不足条件。 T1 和 T2 使用相同类型的热敏电阻，以便使它们具有相同的标称电阻值。当电
池为环境温度， TEMP 端电压为 lV( 参考点为 BATT- 端)。
T囚的门限选择置快速充电的结束点。只要 TMEP 端电在-超过 THI 端电压，快速充电就结束。
TEMP 端电压下降到低于 THI 端电压后，快速充电不会重新开始。
TLO 门限选择决定不启动快速充电的低温度。如果当 M1也712/MAX713启动时，
则快速充电将不会进行.除非到 TLO 低于 TEMP 时。
TLO>TEMP ,
.
一-.
-203
i
通过去掉 R5 ， T3 和 0.022μF 的电容，将 TLO 端连接到 BATT-- 端，低温充电启动无效。
去掉旦、T2、 T3 、阳、阳、郎和它们的辅助电容，并按以下连接: TEMP=REF 、四=飞、
.，2·TLhBATT-，整个温度比较器充电关断装置无效。
看些工电池的一封生内有一个温度检测热敏电阻连接在电池的负极性端。这种情况中，使用图
ll(b) 所示的结构，如果绝对温度充电关断可以接受，热敏电阻 T2 和 T3 可被标准的电阻替代。
副'ftOMAl
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T2 ANO 1'3 MAY BE
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NOπ: FOR A8S 0LU lC !ThI PE!lATURE CHARGE CUTO仔. T2 ANOηMAYBE
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图l1 (b) 另一种温度比较器结构
温度比较器
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MAXl13
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MAX713 对三节 NiMH 电池充电特性 图 17 提供多节电池充电的共射共基连接
图 16
..
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图 18
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最简单的开关模式充电器
哺
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205
,
三 J 应用说明
5.1 气开美模式工作-
·在晶体管的功耗不能容忍的应用中(例如:散热不可行或者太昂贵) .可设计开关模式充电
器。
开关模式工作可使用图组所示电路实现。图 21 所示电路在 CC 端使用误差放大器作为比较器，
此比较器用 33pf 的争夺增加滞后 J图 2 所示的结构对两节电池以1A电流元电?通过改变 RSENSE
和 PGMO 到 PGM3 的连接;二可得到更大的充电电流，以及对更多的电池充电。使用图 2 所示电路的
开关注形图如图 22 所示。增加连接在 cc 端和 BATT.... 端之间电容的值，可降低开关频率。必须注
意，连接在 CC 端的两个电容，应尽量靠近 MAX也jMAX713 CC 管脚放置，并使它们的引线是短，
cc 节点为高阻挠点，所以不要使逻辑线靠近 cc 端。图 21 所示电路在充电时，不能接负载。在固
定频率开关模式工作条件下 I MAX712/MAX713与低价格的 ICM7弱6 和 MAX738 的接口如图坦和图 24
所示。:":'~二^
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206
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AC-DC 变换器
5.2
交流到直流变换器可直接插入交流电中，它的典型组成为:一个变压器、-个全波替式整
流器和一个电容器。图 12 、图 14 示出了三种消费产品 AC-DC 变换器的特性。所育三种变换器都
存在 120Hz 1皆波的输出纹波电压。当选择 MAX'π21MAX713 使用的变换器时，必须注意，对快速充
电负载，适配器的最低输出电压至少应比电池的最高电压高 1 伏。
电池充电举例
5.3
使用 MAX7l2和MAX7l3，以1A的电流对3节 AA
l1XX>mAh NiMH电池(型号 GP1COOAAH)充电的结
果如图 15 和图 16 所示。在典型工作电路中使用图 11( 的所示的热敏电阻连接形式。
DC IN- 索尼 AC-190 ， +9V DC 800mA 输出 AC-DC 变换器
PGMO-V... , PGMl...REF , PGM2=REF , PGM3=REF ,
Rl-200Q , R2罩 150 Q , RSICNSIC-O. 25 Q ,
Cl=1μF ，
C2=O.01μF ， C3-10μF ，
VLIMIT REF ,
",
R3 ,.,10k Q , R4=15k Q
T2 型号 13AI002( Alpha 热敏电阻 800-235-5445)
Tl ,
R5 省略.
5.4
T3 省略.
TLO==BATT-
多节串联电池情况
当 MAX712/M AX713 上电时， BATI'...端的极限参数提高。如果对口节以上的电池进行充电，当
、
DC
IN.没有使用时，
5.5
BATT... 端输入电压必须由外部电路限制(旦因 17) 。
不充电期间效率
电流敏感电阻 RSICNàIC 在电池使用期间，引起较小的效率损失 3 如果 RSICNSÈ:较电;也组的内阻
大很多，效率的损失才会较大。无论电濡是否加在充电器上，使用并联感应电盟的电路如图 18
所示。
5.6
状态输出
用逻辑电平指示充电器状态的电路如图 19 所示。图 20 所示电路可用于蕴动 LED ，指示上电
和充电器状态。
•
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飞 $1111
MAX712/713 快速充电控制芯片在小型
后备电源设计中的应用
哈尔滨工业大学 (150001)
摘要
张东来
王晓冬徐殿国
文章介绍了美国 MAXIM 公司的 MAX712/713 快这龙也控制AZ片在小哩!后备电源尤
龟电路中伪应用，给出了铅政免锥护蓄电池，和妹铺蓄电池的尤电电路参款和对两种充电免池的充电特
性曲线检圳的实验结果。结果表明:该充电电路的应用对象不仅是练铺蓄电池，还可以是铅段先锥护蓄
电池，并得出结论:空载时，对铅段先维护蓄电池，充电最好选用 MAX712; 带载时，最好选用 MAX7130
关键词快速元电
,
铅酸免维护蓄电池媒锅蓄电池
涓流充电
在便携式仪器中，经常需要设计小型后备电源，以
路完成过欠压监控，从电网供电切换到涓流充电的电
便在有交流电网供电时可从电网中摄取能量直接供给
位差消除和 DC/DC 变换等功能.因而，该电源设计
负载，同时给蓄电池充电;另一方面又可随身携带至野
中，充电电路的性能是比较关键的o 我们采用 MAX
外作、屯，电源原理框图见图 1. 图 1 中，监控及辅助电
712/713 快速充电控制芯片，设计了一个性能稳定、可
表1
引脚
称 l
名
班 AX712/713 管脚说明
功
能
d
V过L设(1I定.M6最
5ITv大连×电接电池池到电j数V压目+，端)若:，否V不则L允1许M电IVT池L连端1M接电I到T压V端不+超端能过，超+电过2池.5端(VV血L.压IM(BITA×EF
电-池BA数?目?))。不能除非超
1
VLIMIT
2
BA片L'T+
3
4
PGMO
PGMl
BAP凹
GM-，O或和者PPGGMM1O决、P定G串m
联充开路电电(见池表的剖数，目决，定通1过到连1接
6节
PG的M粤0池、P数G。M1 到 V+、 RE:F'或
5
THI
过温度比较器的跳转点，如果 TEMP 端电庄上升超过 THI 端电压，快速充电结束。
6
TLO
'
电池的正端。
'
--
电温被禁度止不小，够工并作比且温较直稽度到的。T跳E转
M点
P ，端如压果上芯升片到在高T于EMTPLO端时电才压开小始子， TTLLOO端必电须压被时置上为电低，快于充速充
电
4
嚣的最
"
"
7
TEMP
8
FASTCHG
•
9
10
PGM2
P G-M3
11
CC
自热敏电阻得到的依赖温度的感应电压输入端。
海极开结路涓快流速充充电电开状始态时输，出F端
A，当芯片对停电止池吸快入速电充流电。时， FASTCHG 吸入电流; 当快
速充电柬
STCHG
-
使速P充PGG电MM到22涓和、P流PG充
GMM3电3开的置路电允〈流见卉比快表例剖速。，充可电置的从最3大3 时分间钟，到通2过64连分接钟到的P
输出、m
时F间，求PGBMAT3还-决，定或者
快
恒定电流调整环路孙偿输入端。
••
电池的负端。
12
BATT-
13
GND
系统地，在 BAT!'-和 GND 之间接一个电阻，用于监视进入电池的电流。
14
DRV
驱动外部-PNP 电流源的电流吸入端。
15
V+
并联稳压器， V+ 端的电压调整到相对于 BATT- 端的+町，并且分流电流驱动 MAX 7J2
-
/713.
, 16"
REF
2.0V 基准挥，提供 1mA 电流输出。
哩吓
-，-、-
《电子技术址-年第 12 期
.
•
'，..~"".蝠，句-
{M7)-19 一
}一'弓~雯雯"""
"阳画画画画}
表s
最大充电时间编程表
输出时间 IA/D采样间隔|斜率检测 IPGM3 连接IPGM2 连接
(min) \
(8)
?
因 11飞型锵电电源设计原理图
.22
靠的快速充电电路。该电路的主要优点是: (1) 可完成
对大容量铅酸免维护电池 (12Y6.5AH) 充电 (2) 充
21
1
效
1
y+ : 1,
开路
:l2
1.21
使能
v+
RE]T
电效率高、速度快，充电速率可达 4C;(3) 可自动完成从 3
33
1
21
无效
v+
v+
快速充电到涓流充电的转换3 因而提高了控制的自动
33
I
21
使能
v+
电池负端
45
I
42
无效
l
开路
!
开路
42
|使能 '1
开路
I
REF
化程度和充电过程峭安全性沃的较高的性能价格比。
与伊、:MAX712/'11S 概述?‘
岳fí"
|
:〈一〉管脚功能及特点
66
142
无效 -i
开路
也MA军7~~1:71~_ 管脚排列如图 2 所示。各管脚说飞
66
I
42
使能
开路
钮
84
无效
明见表 1 所列.
佣
9
o
VLIMIT~飞广Ill REF
俨
,. \
••
Úl.~二--，阳时，?!，
、;
THr~
呻←-BATT
T飞hJ斗了气;二
FASTCHG -Jl.f
'~CC
飞
l?GM1 连接
1
v+
v+
2
开路‘
v+
3
REF
'
-,
v+
"5
1、 v+
开路
6
开路
,
无效
|电池负端
使能
|电池负端
β t<，;F
v+
l
电池负端‘
自动壳成由快速充电到涓流充电的切换;当不充电时，
电池的最大泄漏电流为 5μA: 可同时对工到 16 节串
联电池充电cLMAXr12 和 MAX713 的唯-不同点是
MAX712 是以当转换结果等于和小于它的原有值〈即
零电压斜率检测〉来结束快速1ê电，而 M4X713 则以
开路
v+
RE J:<'
开路
REF
s
12
电池正端
REF
V+
电池负端
开路
电池负端
-=-L~O.寸i饵'
I
|电池负端|
电池负端
啊'
REF
16
,
-气
使能
开路
h
REF
工5' 气 r.;.:
、-一吧宁-啊-\-四唱-而嘲-，
;BE Jr
'同年
11
14
， 咀
1 兰辛艺
U
_1 电池瞅负此此|
一
开稍晓 .
-,---,-\--,
当转换结果至少小于它的原有值〈即负电压斜率检测?
i
13
REF
来结束快速充电。
9"、 t电; ~ -: .且、
10
RJ:tJF 二"，1 俨I 父
电;由电压斜率、温度和定时器决定快速充电的关断，
~
ι. 、‘
168
开路
开路
7
8
168-
I
REF
量;可完成从 013 到 40 的快速充电及。/岛的涓流充
一 v+
电池正端
……
264
电池负端
该芯片的特点是充电时p 可给电池的负载提供能
PGMO 连·接!
电池数
--'4
168
264
电池数目编程表
a
180 1
l
l 百?÷下
南
J，一E
函卢;;-1 ， 'v+
币i汇τηI
盯 酣
RB即:F
事池负端
i
MAX712/713 管脚排列俯视图
J 表 2'
钮
归
84
~O_J_16臼8
-PGM3
FιPGM2
DIP/SO
1 ' 8 4 4 1 使能
丁z
町l
丁z
町
卜 GN[)
.., 'TEMP'; . . ! . f •
图 2
9ωo
•, DRV
4
~， p倒1 升， Mf，X712l7 13
,
",:-
v
BATT+
|
v+
if
RRF
'电\'.
电池负端.
.
' 电怆负端
电池负端
〈二〉对电池数目和最大充电时间的编程
MAX7正2/713 在使用前要对电池数目和最大充
电时间进行编程‘所谓电池数目的编程即是依据被充
(，'电电池串联的总电压而定，具体计算如下:
1
当 VL;I:M;IT 接 y+ 端时P
N=lNT(U总 /1.6号)+工
当 VLIMIT 接 REF 端时p
N 二I:Nr，r CQ 且 1 2 )+1
式中 N 为编程数， "U边为所要充电电池串联的总电压
•
l
〈单位为 V)? 函数 f(a;) ~ì茸叭的为:取整函数〈仅取结
果的整数部分〉。
电池编程数目按表 2 通i在连接 EGMt.. PGMO 到
近电F票热号则在第月期
守
相应端口市完成;最大充电时昭则依据充电速率而定，
关断。一般按如下方式连接: TEMP ""， R~F， 'THI=
按表 3 通过连接飞P:GM3.. PGNI2 ~U，相应端同而完成。
V 勺 TLO 二IfATT"':，使整个温度比较器充电关断装
其中， PQ-M 3.决定涓流充;也电流的大小〈如表功。
置无效F 充电的状态由电压斜率和定时器来决定。
h 表"
(3) M冉孚7正2/n3 的外部;DC 功率:~其最小输
出电压〈包括纹波〉必须高于 6γ，且至少比最大电池
'PGMB 决定涓流充电电珑的大小
PGM13;1
快速充电速率
‘
E
| 涓流充电电流
电压高 lV，否则将不工作或工作不正常，如若外部电
‘坠，.，.
V i:
4c
1 1 .. s也 /64
源电压小于(最大电池电压 +lV)" 则会导致工作到
t 开路
20
1f8st/132
某段时间时芯片发热等现象。
REF
C
1 f8st /16
0/2
I 18•t/8
(4) B 1 参数由下式选择
电池负端
R 1 =(DC 电源最小电
压 ~5V)/5mA(单位为 kO) 。
国
(5) R，向脚由下式选择 R.， n ..-O.25 Vl1t酬，其
一一一二
MAX712/713 典型军作电路如图 3(的。其中
PGMO、 PGM1， PGM2、 PGM3 的连接由电池数目和
最大充电时间编理决定"在应用中 3 充电状态一般应
有所指示 F 指示电路如图 3(的，当快速充电时，发光二
中 If:ult Ý5J快速充电电流， Iìast= 电池容置之IDA)I充电
小时数 (h) 。
三、对铅酸免维妒曹电池和锦铺蓄电池
究电特性曲线的检测和分析工
极管亮;进入涓流充电时，发光二极管熄灭。
我们采用 ~AX712/713 的典型电路3 如表 5 所
列设定参数及充电初始状态j 两种芯片对两种电池带
，直流 .b，，，..;
载和空载情况下的充电特性曲线如图垒。所示。由于镶
丘主叩
、
v
、
..
、/
锯电池在充电过程中，先经恒流快速充电，电池前压升
高，至饱和眉p 端压出现负斜率;~AK712/7妇在带载
和空载的情况下均可迅速从快速充电状态切换至1月流
充电状态〈如图旬， 4c); 而铅酸免维护蓄电池的特性
则不同 F 在快速充电过程中 P 无论是否带载端压始终不
会出现零斜率增长p 故用 MAX713 充电时ι 充电电流
从电压曲线的拐点处开始以指数规律衰减〈如图 4町，
电
路
叫作
工
h型
鸣。
，典
，、、'。且
4
呼
‘用一
川
WJ
MA X"'
而 MA~7~2 则在检测到零斜率增长时便迅拉切换至
泪流充电状态〈女口图 4哟，这也是两者不同之处@
另外，由于充电时，一般采用全浮克运行方式，即
外部 DC 功率源一宙给负载供电，一面对蓄电池浮充，
表b
V卢
e
镖锡、铅酸兔维护蓄电池充电电路参数配置
2k
MAX712/713
I
飞
·、
‘-曹
、. ...'.、
Jι
~
•
电池
镇铺蓄电池
图 3 '.. ~AX;112/1时型立作电路及快速充电指示电路
充电电路|最大充电时间半部分错!最大注电时间 ~264 分钟
ι-v
i
I 电池编程安fr~1
11h=4∞ 0:;
^;
IRseu 剧目 0.250
吨
阳镜 =80
IUi~=1V
,
IR1=:， 2 凶
JSsen归 =0.1[:)"
JR~.-200
巾↑ U in -15V
二、宽电电醋的设计步骤及钳选择
一-1'VL'IMIT= REr
充电电路的设计步骤及参数选择如下=
充电初拚l 充足电的同节家用五号|充足于电的主密封铅酸
':(均选择电池编程数「目及最大充电时间.
,;,
铅酸免维护蓄电池
|
参数配置|电池编程数 =2
FAS 'rCHG
⑦)快速充电揭示电路
可
及充电初始状态
…
(2); 选择电池'充电结束方法.决定电池充电结束
最重要的参数是电池电压、内压力和温度øMAX 712
1713 是由电压僻、温度和定时器来对快速充电的
状态|锦铺蓄电池 (500 皿A!h)!免维护蓄电'i<~ Pan~吨io'
也|以 lA 放电 10 分掉-， l~o耳边 V6. ， ;P (平{飞:
"':.:',
、
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ι 、二、?.弘:h/到百乃以 3~5'A放
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充电时间(
注:叫〉一带载电压
』兮毛-带载电流
、&
20
25
30
Yê 电时间(
min)
•
一←细晖'
min)
泣:一0→带载也压
一十一空载电压
-争等-带载电流
-...…3~我咆ÌllC
-:;Å-空我也流
(b) M.AX713 对铅酸免维护蓄电池充电特性曲线
(α:) M'AX713 对镰铺蓄电池充电特性曲线
3.6
2.4
14
13.8
0.2
\2.6
AU
0
5
10
15
20 25
充电时间( min >
位;一O一带裁电压
二争毛一带载电流
命
30
确吨"，
2.4
CJ
0
60
20
80
o
究电时间( min)
注:-0一带载电压...;二十一空载电压
一十一空毒量也应 i
F叮~~运载电流
一善毛一带载电流
。i) MAX712 对镰铺蓄电池充电特性曲线
图 4.
12.4
-企「主载电流
(à) MAX712 对铅酸免维护蓄电池充电特性曲线
MAX712/713 对镰铺蓄电池和铅酸免维护蓄电池充电特性曲线
DC/DC 变换或采用稳压装置加以消除，如图 5 所示。，
4mH
Vòút
四、
到负辑.
.....
#舍
论
由上述实验可知F 对镰铺蓄电池充电，无论是带载
还是空载 P 选用 MAX712/713 均可.对铅酸免维护
蓄电池来说p 空载充电时由于电池电压最终产生零斜
率增长 3 故最好选用 MAX712; 而带载充电时p 若用
1μ
困 5
MAX712 当由充电状态切换至涓流充电时p 负载的部
全浮充运行方式电压 DC/DC 调整
图中 V o 的 =;5.05x
(1 + R:t!R2) ，单位为
V
分能量将由电池提供p 此时电池端压将始终成下降趋
以补偿蓄电池自放电和独立供电时消耗的能量.但蓄
势，且不能自动复充电p 而 MAX713 则可以自动解决
离地由浮充转入独立供电或由独立供电转入浮充供
这个问题，还能自行完成从垣流到恒压的均衡充电过
也加之从快速充电切换至涓流充电时p 电池端庄都将
程F 这正是充电过程的最佳方式.基于上述 p 我们最后ι
发生变化咽此必绩调整:在后级采用宽范国输入的
-22 一〈刷〉
选用了性能/价格比较高的 M .aX713~ .
与电子技术组栅年第 U 期
!is}
电动自行车充电器方案
在我国一些大中城市，为弥补公共交通能力的不足，流行着一种燃油助动车。这种车辆使
用单缸二充程然油机，污染排放极大，严重影响了城市环境卫生和城市居民的健康。为此，开
发一种无污染排放的短程、轻便电动自行车，以逐渐取代目前使用的燃油助动车，不仅在防止
环境污染和节约自然资源方面有着重大的实际意义，而且也是目前城市市民普遍关心和急待解
决的问题。
80 年代曾一度兴起的电动自行车开发研究，因电机效率过低，充电设备落后，电油寿命过
短等原因而冷落下来。目前，供电动自行车配套的各种辅助部件的性能相继有重大突破。例如，
新型变频式低速(~24km/h) 无刷永磁电机，其效率提高到 85% 以上，充电器开始智能化，传动
和控制系统更加轻便可靠。从整车开发的技术难度而言，欲取得商业上的成功，最为关键的仍
然是其动力部分，尽管一些新型化学电源，例如镇氢电池、理离子电池已大量进入市场，但铅
酸电池、镇铺电池仍以价格低、技术成熟的优势被公认为是电动自行车中最为现实的动力电源，
特别是镰铺电池，其低内阻特性对于这种需大电流放电的应用更具吸引力。
目前，电动自行车主要配备的电池是
12V 或 24V 、 17Ah - 22Ah 铅酸电池或镇铺电池，另
外，一些短程轻便型电动助力车大多使用 6V 、
悦嗣
6Ah--8Ah 铅酸电池或镰铺电池。电池节数低于
16 节时，选用 MAX713 较为方便(如图所示)。
利用 MAX713 可对电池进行快速充电，充电速率
为: C/4一-4 ，快充终止方式为:电压斜率检测、
8AfT.φ
温度检测、超时检测、最大电压限制，快充终
且fF
.-.AX1Ao帽
止后可自动转换成涓流充电，设计电路如图一
品fAX7I2
MAX713
所示。
对于 17Ah--22Ah 铅酸电池或银锅电池的
充电器设计大多采用图二所示方案，降压型
DC-DC 转换器用于为充电控制器提供合适的供
电电压，开关电源将 WALL CUBE 的输出转换成
图一、 1-16.节lI 1cd电池充电器
电池快速充电所要求的电流，充电
WALl
控制器大多选用 MAX200挝、 BQ2003 、
口JBf
BQ2031 等充电控制芯片或用微处理
器。
图三所示电路，提供了一种直
开央电菁、
接用控制器控制 AC-DC ，实现大电池
(即-oc)
组充电的方案。图中， AC一DC 采用反
激式无工频开关电源，具有体积小、
重量轻，功耗低、效率高等特点。
通过 A 、 B 连接与否满足不同输入电
忽阳
压的要求。即在 220V 工作时，可单
相桥式整流， 110V 工作时，可单向
倍压整流，两种情况下，均得到约
300V 的直流电压。此直流电压接向原边绕组 Lpo
在反激式变换器中，由于开关关断时，漏电感引起开关集电极电压突然升高:或负载线不
够合理，会造成较高的开关应力(导致开关管损坏 7 。为抑制开关应力有两个办法:一是靠工艺
减小漏电感，二是依靠与电感线圈荐联的 Rc 、 C2 缓冲器耗散过电压能量，通过附加线圈和定向
二极管将能量反馈回电源。
.
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图三、大电池组充电方案
e
充电控制器选用 MAX2003A ，外部元件的选择可参考一下步骤:
①、直流电源:电池节数 x 最大节电压+ 1
(V)
②、按照充电速率确定充电电流 I FAsT ，最大充电时间。应注意充电效率不是 100% ，实际
，充电时间应比理论值多出 30%左右。
③、由快充电流确定电流检测电阻
RSN~ = 0.235/ IFAsT
④、有电池节数确定 RB l' RB2 : RB1 、 RB2 之和应在 100k 与 500k 之间
RB2
=RB/ (电池节数-1)
⑤、根据需要选择温度控制元件等
图三中的充电控制器也可以用 MAX713 替代，注意选用 MAJÇ713 时应将电池电压分压后
连接到 MAX713 的 BATT+ 引脚。 MAX713 相对 MAX2003A 价格较低。
以上推荐的方案也可用于为其它应用的大电池组充电，例如:电信系统的 48V 电池组、
叉车配备的大电池组等。
4
P
..
19-0100; Rev 6; 12/08
KIT
ATION
EVALU
E
L
B
A
IL
AVA
NiCd/NiMH Battery
Fast-Charge Controllers
The MAX712/MAX713 fast-charge Nickel Metal Hydride
(NiMH) and Nickel Cadmium (NiCd) batteries from a DC
source at least 1.5V higher than the maximum battery
voltage. 1 to 16 series cells can be charged at rates up
to 4C. A voltage-slope detecting analog-to-digital converter, timer, and temperature window comparator determine
charge completion. The MAX712/MAX713 are powered
by the DC source via an on-board +5V shunt regulator.
They draw a maximum of 5µA from the battery when not
charging. A low-side current-sense resistor allows the
battery charge current to be regulated while still
supplying power to the battery’s load.
The MAX712 terminates fast charge by detecting zero
voltage slope, while the MAX713 uses a negative
voltage-slope detection scheme. Both parts come in 16pin DIP and SO packages. An external power PNP transistor, blocking diode, three resistors, and three
capacitors are the only required external components.
The evaluation kit is available: Order the MAX712EVKITDIP for quick evaluation of the linear charger.
________________________Applications
Battery-Powered Equipment
Laptop, Notebook, and Palmtop Computers
Handy-Terminals
Cellular Phones
Portable Consumer Products
Portable Stereos
Cordless Phones
Features
♦ Fast-Charge NiMH or NiCd Batteries
♦ Voltage Slope, Temperature, and Timer
Fast-Charge Cutoff
♦ Charge 1 to 16 Series Cells
♦ Supply Battery’s Load While Charging
(Linear Mode)
♦ Fast Charge from C/4 to 4C Rate
♦ C/16 Trickle-Charge Rate
♦ Automatically Switch from Fast to Trickle Charge
♦ Linear Mode Power Control
♦ 5µA (max) Drain on Battery when Not Charging
♦ 5V Shunt Regulator Powers External Logic
Ordering Information
PART
TEMP RANGE
0°C to +70°C
16 Plastic DIP
MAX712CSE
MAX712C/D
MAX712EPE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
16 Narrow SO
Dice*
16 Plastic DIP
MAX712ESE
MAX712MJE
-40°C to +85°C
-55°C to +125°C
16 Narrow SO
16 CERDIP**
Ordering Information continued at end of data sheet.
*Contact factory for dice specifications.
**Contact factory for availability and processing to MIL-STD-883.
Typical Operating Circuit
Q1
2N6109
DC IN
VLIMIT 1
16 REF
BATT+ 2
15 V+
D1
1N4001
V+
C1
1μF
VLIMIT
BATT+
REF
14 DRV
PGM0 3
THI 5
DRV
THI
WALL
CUBE
TOP VIEW
R2
150Ω
C4
0.01μF
R1
Pin Configuration
PGM1 4
PIN-PACKAGE
MAX712CPE
MAX712
MAX713
12 BATT11 CC
TLO 6
R3
68kΩ
13 GND
MAX712
MAX713
BATTERY
C3
10μF
TEMP
10μF
R4
22kΩ
LOAD
CC BATT- TLO GND
10 PGM3
TEMP 7
9
FASTCHG 8
PGM2
C2
0.01μF
RSENSE
DIP/SO
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
1
MAX712/MAX713
General Description
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
ABSOLUTE MAXIMUM RATINGS
V+ to BATT- .................................................................-0.3V, +7V
BATT- to GND ........................................................................±1V
BATT+ to BATTPower Not Applied............................................................±20V
With Power Applied ................................The higher of ±20V or
±2V x (programmed cells)
DRV to GND ..............................................................-0.3V, +20V
FASTCHG to BATT- ...................................................-0.3V, +12V
All Other Pins to GND......................................-0.3V, (V+ + 0.3V)
V+ Current.........................................................................100mA
DRV Current. .....................................................................100mA
REF Current.........................................................................10mA
Continuous Power Dissipation (TA = +70°C)
Plastic DIP (derate 10.53mW/°C above +70°C............842mW
Narrow SO (derate 8.70mW/°C above +70°C .............696mW
CERDIP (derate 10.00mW/°C above +70°C ................800mW
Operating Temperature Ranges
MAX71_C_E .......................................................0°C to +70°C
MAX71_E_E .................................................... -40°C to +85°C
MAX71_MJE ................................................. -55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(IV+ = 10mA, TA = TMIN to TMAX, unless otherwise noted. Refer to the Typical Operating Circuit. All measurements are with respect to
BATT-, not GND.)
PARAMETER
V+ Voltage
CONDITIONS
5mA < IV+ < 20mA
IV+ (Note 1)
MIN
TYP
4.5
MAX
5.5
5
BATT+ Leakage
V+ = 0V, BATT+ = 17V
BATT+ Resistance with Power On
PGM0 = PGM1 = BATT-, BATT+ = 30V
UNITS
V
mA
5
µA
30
kΩ
C1 Capacitance
0.5
µF
C2 Capacitance
5
nF
REF Voltage
0mA < IREF < 1mA
1.96
2.04
V
Undervoltage Lockout
Per cell
0.35
0.50
V
External VLIMIT Input Range
1.25
2.50
V
THI, TLO, TEMP Input Range
0
2
V
-10
10
mV
THI, TLO Offset Voltage (Note 2)
0V < TEMP < 2V, TEMP voltage rising
THI, TLO, TEMP, VLIMIT Input Bias Current
-1
1
µA
VLIMIT Accuracy
1.2V < VLIMIT < 2.5V, 5mA < IDRV < 20mA,
PGM0 = PGM1 = V+
-30
30
mV
Internal Cell Voltage Limit
VLIMIT = V+
1.6
1.65
1.7
V
mV
Fast-Charge VSENSE
Trickle-Charge VSENSE
Voltage-Slope Sensitivity (Note 3)
225
250
275
PGM3 = V+
1.5
3.9
7.0
PGM3 = open
4.5
7.8
12.0
PGM3 = REF
12.0
15.6
20.0
PGM3 = BATT-
26.0
31.3
38.0
MAX713
-2.5
MAX712
0
mV
mV/tA
per cell
Timer Accuracy
-15
15
%
Battery-Voltage to Cell-Voltage
Divider Accuracy
-1.5
1.5
%
DRV Sink Current
2
VDRV = 10V
30
_______________________________________________________________________________________
mA
NiCd/NiMH Battery
Fast-Charge Controllers
(IV+ = 10mA, TA = TMIN to TMAX, unless otherwise noted. Refer to the Typical Operating Circuit. All measurements are with respect to
BATT-, not GND.)
PARAMETER
CONDITIONS
MIN
FASTCHG Low Current
V FASTCHG = 0.4V
FASTCHG High Current
V FASTCHG = 10V
A/D Input Range (Note 4)
Battery voltage ÷ number of cells programmed
TYP
MAX
UNITS
2
mA
1.4
10
µA
1.9
V
Note 1: The MAX712/MAX713 are powered from the V+ pin. Since V+ shunt regulates to +5V, R1 must be small enough to allow at
least 5mA of current into the V+ pin.
Note 2: Offset voltage of THI and TLO comparators referred to TEMP.
Note 3: tA is the A/D sampling interval (Table 3).
Note 4: This specification can be violated when attempting to charge more or fewer cells than the number programmed. To ensure
proper voltage-slope fast-charge termination, the (maximum battery voltage) ÷ (number of cells programmed) must fall
within the A/D input range.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
CURRENT-SENSE AMPLIFIER
FREQUENCY RESPONSE (with 15pF)
CURRENT-SENSE AMPLIFIER
FREQUENCY RESPONSE (with 10nF)
MAX712/13 toc01
40
MAX712/13 toc02
20
C2 = 15pF
FASTCHG = 0V
0
10
+
VIN
-
CC
+
CURRENTSENSE
AMP
GND
-40
Φ
-80
-10
-120
-20
-80
VOUT
-
BATT-
-20
1k
0
100k
10k
1M
10M
-120
10
FREQUENCY (Hz)
SHUNT-REGULATOR VOLTAGE
vs. CURRENT
1
5.2
5.0
DRV SINKING CURRENT
4.8
4.6
MAX712/13 toc05
1.6
TEMP PIN VOLTAGE (V)
5.4
V+ VOLTAGE (V)
10
DRV NOT SINKING CURRENT
5.6
ALPHA SENSORS PART No. 14A1002
STEINHART-HART INTERPOLATION
MAX712/13 toc04
5.8
MAX712/13 toc03
DRV PIN SINK CURRENT(mA)
FASTCHG = 0V, V+ = 5V
10k
FREQUENCY (Hz)
CURRENT ERROR-AMPLIFIER
TRANSCONDUCTANCE
100
1k
100
35
1.4
30
1.2
25
1.0
20
0.8
15
0.6
10
0.4
5
4.4
4.2
0.1
1.95
4.0
1.97
1.99
2.01
VOLTAGE ON CC PIN (V)
2.03
2.05
0.2
0
10
20
30
40
CURRENT INTO V+ PIN (mA)
50
60
BATTERY THERMISTOR RESISTANCE (kΩ)
BATT-
-10
-40
0
AV
GAIN (dB)
AV
Φ
PHASE (DEGREES)
GAIN (dB)
10
0
40
C2 = 10nF
FASTCHG = 0V
PHASE (DEGREES)
20
0
0
10
20
30
40
50
60
BATTERY TEMPERATURE(°C)
_______________________________________________________________________________________
3
MAX712/MAX713
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX713
NiCd BATTERY CHARGING
CHARACTERISTICS AT C RATE
MAX713
NiMH BATTERY CHARGING
CHARACTERISTICS AT C RATE
MAX712/13 toc06
30
25
1.40
30
60
30
1.50
T
25
1.45
90
0
30
60
CHARGE TIME (MINUTES)
MAX713
NiCd BATTERY-CHARGING
CHARACTERISTICS AT C/2 RATE
MAX713
NiMH BATTERY CHARGING
CHARACTERISTICS AT C/2 RATE
MAX712/13 toc09
V
30
T
25
1.40
0
50
100
CELL VOLTAGE (V)
1.45
35
CELL TEMPERATURE (°C)
CELL VOLTAGE (V)
1.55
ΔV
CUTOFF
Δt
1.50
1.50
35
V
1.45
30
T
1.40
0
150
MAX713
CHARGING CHARACTERISTICS OF A
FULLY-CHARGED NiMH BATTERY
40
1.55
35
30
T
1.45
4
MAX712/13 toc11
25
5
10
15
20
V
1.60
CELL VOLTAGE (V)
ΔV
CUTOFF
Δt
CELL TEMPERATURE (°C)
1.60
CHARGE TIME (MINUTES)
100
50
150
CHARGE TIME (MINUTES)
1.65
5 MINUTE REST
BETWEEN CHARGES
V
25
MAX713
CHARGING CHARACTERISTICS OF A
FULLY CHARGED NiMH BATTERY
MAX712/13 toc10
1.65
40
ΔV
CUTOFF
Δt
CHARGE TIME (MINUTES)
0
90
CHARGE TIME (MINUTES)
MAX712/13 toc08
1.50
35
40
ΔV
CUTOFF
Δt
1.55
35
5-HOUR REST
BETWEEN CHARGES
1.50
30
T
25
1.45
0
5
10
15
CHARGE TIME (MINUTES)
20
_______________________________________________________________________________________
CELL TEMPERATURE (°C)
0
ΔV
CUTOFF
Δt
V
CELL TEMPERATURE (°C)
T
1.45
1.55
CELL TEMPERATURE (°C)
35
40
1.60
CELL VOLTAGE (V)
ΔV
CUTOFF
Δt
V
1.50
CELL TEMPERATURE (°C)
CELL VOLTAGE (V)
MAX712/13 toc07
40
1.55
CELL VOLTAGE (V)
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
NiCd/NiMH Battery
Fast-Charge Controllers
PIN
NAME
FUNCTION
1
VLIMIT
Sets the maximum cell voltage. The battery terminal voltage (BATT+ - BATT-) will not exceed VLIMIT x
(number of cells). Do not allow VLIMIT to exceed 2.5V. Connect VLIMIT to VREF for normal operation.
2
BATT+
Positive terminal of battery
3, 4
PGM0,
PGM1
PGM0 and PGM1 set the number of series cells to be charged. The number of cells can be set from
1 to 16 by connecting PGM0 and PGM1 to any of V+, REF, or BATT-, or by leaving the pin unconnected
(Table 2). For cell counts greater than 11, see the Linear-Mode, High Series Cell Count section.
Charging more or fewer cells than the number programmed may inhibit ΔV fast-charge termination.
5
THI
Trip point for the over-temperature comparator. If the voltage-on TEMP rises above THI, fast charge ends.
6
TLO
Trip point for the under-temperature comparator. If the MAX712/MAX713 power on with the voltage-on
TEMP less than TLO, fast charge is inhibited and will not start until TEMP rises above TLO.
7
TEMP
8
FASTCHG
Open-drain, fast-charge status output. While the MAX712/MAX713 fast charge the battery, FASTCHG
sinks current. When charge ends and trickle charge begins, FASTCHG stops sinking current.
9, 10
PGM2,
PGM3
PGM2 and PGM3 set the maximum time allowed for fast charging. Timeouts from 33 minutes to 264
minutes can be set by connecting to any of V+, REF, or BATT-, or by leaving the pin unconnected
(Table 3). PGM3 also sets the fast-charge to trickle-charge current ratio (Table 5).
11
CC
12
BATT-
Negative terminal of battery
13
GND
System ground. The resistor placed between BATT- and GND monitors the current into the battery.
14
DRV
Current sink for driving the external PNP current source
15
V+
Shunt regulator. The voltage on V+ is regulated to +5V with respect to BATT-, and the shunt current
powers the MAX712/MAX713.
16
REF
2V reference output
Sense input for temperature-dependent voltage from thermistors.
Compensation input for constant current regulation loop
_______________________________________________________________________________________
5
MAX712/MAX713
Pin Description
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
Getting Started
The MAX712/MAX713 are simple to use. A complete
linear-mode fast-charge circuit can be designed in a
few easy steps. A linear-mode design uses the fewest
components and supplies a load while charging.
1) Follow the battery manufacturer’s recommendations
on maximum charge currents and charge-termination
methods for the specific batteries in your application.
Table 1 provides general guidelines.
Table 1. Fast-Charge Termination Methods
Charge
Rate
NiMH Batteries
NiCd Batteries
> 2C
ΔV/Δt and
temperature,
MAX712 or MAX713
ΔV/Δt and/or
temperature, MAX713
2C to C/2
ΔV/Δt and/or
temperature,
MAX712 or MAX713
ΔV/Δt and/or
temperature, MAX713
< C/2
ΔV/Δt and/or
temperature, MAX712
ΔV/Δt and/or
temperature, MAX713
2) Decide on a charge rate (Tables 3 and 5). The slowest fast-charge rate for the MAX712/MAX713 is C/4,
because the maximum fast-charge timeout period is
264 minutes. A C/3 rate charges the battery in about
three hours. The current in mA required to charge at
this rate is calculated as follows:
IFAST = (capacity of battery in mAh)
–––––––––––––––––––––––––
(charge time in hours)
Depending on the battery, charging efficiency can be
as low as 80%, so a C/3 fast charge could take 3 hours
and 45 minutes. This reflects the efficiency with which
electrical energy is converted to chemical energy within
the battery, and is not the same as the powerconversion efficiency of the MAX712/MAX713.
3) Decide on the number of cells to be charged (Table 2).
If your battery stack exceeds 11 cells, see the LinearMode High Series Cell Count section. Whenever
changing the number of cells to be charged, PGM0
6
4)
5)
6)
7)
and PGM1 must be adjusted accordingly. Attempting
to charge more or fewer cells than the number programmed can disable the voltage-slope fast-charge
termination circuitry. The internal ADC’s input voltage range is limited to between 1.4V and 1.9V (see
the Electrical Characteristics), and is equal to the
voltage across the battery divided by the number of
cells programmed (using PGM0 and PGM1, as in
Table 2). When the ADC’s input voltage falls out of
its specified range, the voltage-slope termination circuitry can be disabled.
Choose an external DC power source (e.g., wall
cube). Its minimum output voltage (including ripple)
must be greater than 6V and at least 1.5V higher
than the maximum battery voltage while charging.
This specification is critical because normal fastcharge termination is ensured only if this requirement is maintained (see Powering the
MAX712/MAX713 section for more details).
For linear-mode designs, calculate the worst-case
power dissipation of the power PNP and diode (Q1
and D1 in the Typical Operating Circuit) in watts,
using the following formula:
PD PNP = (maximum wall-cube voltage under
load - minimum battery voltage) x (charge current
in amps)
Limit current into V+ to between 5mA and 20mA. For a
fixed or narrow-range input voltage, choose R1 in the
Typical Operation Circuit using the following formula:
R1 = (minimum wall-cube voltage - 5V)/5mA
Choose RSENSE using the following formula:
RSENSE = 0.25V/(IFAST)
8) Consult Tables 2 and 3 to set pin-straps before
applying power. For example, to fast charge at a
rate of C/2, set the timeout to between 1.5x or 2x the
charge period, three or four hours, respectively.
_______________________________________________________________________________________
NiCd/NiMH Battery
Fast-Charge Controllers
Table 3. Programming the Maximum
Charge Time
NUMBER
OF CELLS
PGM1
CONNECTION
PGM0
CONNECTION
1
V+
V+
2
Open
V+
3
REF
V+
4
BATT-
5
TIMEOUT
(min)
A/D
SAMPLING
INTERVAL
(s) (tA)
VOLTAGESLOPE
TERMINATION
PGM3
CONN
PGM2
CONN
22
21
Disabled
V+
Open
22
21
Enabled
V+
REF
V+
33
21
Disabled
V+
V+
V+
Open
33
21
Enabled
V+
BATT-
6
Open
Open
45
42
Disabled
Open
Open
7
REF
Open
45
42
Enabled
Open
REF
8
BATT-
Open
66
42
Disabled
Open
V+
9
V+
REF
66
42
Enabled
Open
BATT-
10
Open
REF
90
84
Disabled
REF
Open
REF
90
84
Enabled
REF
REF
84
Disabled
REF
V+
11
REF
12
BATT-
REF
132
13
V+
BATT-
132
84
Enabled
REF
BATT-
180
168
Disabled
BATT-
Open
180
168
Enabled
BATT-
REF
264
168
Disabled
BATT-
V+
264
168
Enabled
BATT-
BATT-
14
Open
MAX712/MAX713
Table 2. Programming the Number
of Cells
BATT-
15
REF
BATT-
16
BATT-
BATT-
V+
+5V SHUNT
REGULATOR
PGM2
GND
PGM3
FASTCHG
TIMED_OUT
BATT-
N
POWER_ON_RESET
TIMER
BATTFAST_CHARGE
PGM2
PGM3
THI
TEMP
TLO
ΔV
DETECTION
ΔV_DETECT
CONTROL LOGIC
IN_REGULATION
DRV
CC
V+
BATT100kΩ
GND
VLIMIT
BATT+
UNDER_VOLTAGE
HOT
TEMPERATURE
COMPARATORS
CURRENT
AND
VOLTAGE
REGULATOR
PGMx
100kΩ
COLD
PGM0
CELL_VOLTAGE
MAX712
MAX713
0.4V
BATT-
REF
PGM1
BATT-
INTERNAL IMPEDANCE OF PGM0–PGM3 PINS
Figure 1. Block Diagram
_______________________________________________________________________________________
7
Detailed Description
CURRENT INTO CELL
1.5
1.4
CELL TEMPERATURE
CELL VOLTAGE (V)
The MAX712/MAX713 fast charge NiMH or NiCd batteries by forcing a constant current into the battery. The
MAX712/MAX713 are always in one of two states: fast
charge or trickle charge. During fast charge, the
current level is high; once full charge is detected, the
current reduces to trickle charge. The device monitors
three variables to determine when the battery reaches
full charge: voltage slope, battery temperature, and
charge time.
VOLTAGE
1.3
TEMPERATURE
0.4
0
A
mA
μA
1
2
1. NO POWER TO CHARGER
2. CELL VOLTAGE LESS THAN 0.4V
3. FAST CHARGE
4. TRICKLE CHARGE
5. CHARGER POWER REMOVED
3
4
5
TIME
When the cell voltage slope becomes negative, fast
charge is terminated and the MAX712/MAX713 revert
to trickle-charge state (time 4). When power is removed
(time 5), the device draws negligible current from the
battery.
Figure 3 shows a typical charging event using temperature full-charge detection. In the case shown, the battery pack is too cold for fast charging (for instance,
brought in from a cold outside environment). During
time 2, the MAX712/MAX713 remain in trickle-charge
state. Once a safe temperature is reached (time 3), fast
charge starts. When the battery temperature exceeds
the limit set by THI, the MAX712/MAX713 revert to trickle charge (time 4).
CELL VOLTAGE (V)
VREF = VLIMIT
THI
TLO
A
mA
μA
2
1
1. NO POWER TO CHARGER
2. CELL TEMPERATURE TOO LOW
3. FAST CHARGE
4. TRICKLE CHARGE
3
TIME
Figure 3. Typical Charging Using Temperature
8
Figure 1 shows the block diagram for the MAX712/
MAX713. The timer, voltage-slope detection, and temperature comparators are used to determine full charge
state. The voltage and current regulator controls output
voltage and current, and senses battery presence.
Figure 2 shows a typical charging scenario with batteries
already inserted before power is applied. At time 1, the
MAX712/MAX713 draw negligible power from the battery. When power is applied to DC IN (time
2), the
power-on reset circuit (see the POWER_ON_RESET signal in Figure 1) holds- the- MAX712/MAX713 in trickle
charge. Once POWER_ON_RESET goes high, the device
enters the fast-charge state (time 3) as long as the cell
voltage is above the undervoltage lockout (UVLO) voltage (0.4V per cell). Fast charging cannot start until (battery voltage)/(number of cells) exceeds 0.4V.
CURRENT INTO CELL
CELL TEMPERATURE
Figure 2. Typical Charging Using Voltage Slope
CURRENT INTO CELL
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
4
1.5
1.4
1.3
A
mA
μA
1
1. BATTERY NOT INSERTED
2. FAST CHARGE
3. TRICKLE CHARGE
4. BATTERY REMOVED
2
3
TIME
Figure 4. Typical Charging with Battery Insertion
_______________________________________________________________________________________
4
NiCd/NiMH Battery
Fast-Charge Controllers
Figure 4 shows a charging event in which a battery is
inserted into an already powered-up MAX712/MAX713.
During time 1, the charger’s output voltage is regulated
at the number of cells times VLIMIT. Upon insertion of
the battery (time 2), the MAX712/MAX713 detect current flow into the battery and switch to fast-charge
state. Once full charge is detected, the device reverts
to trickle charge (time 3). If the battery is removed (time
4), the MAX712/MAX713 remain in trickle charge and
the output voltage is once again regulated as in time 1.
battery pack is higher during a fast-charge cycle than
while in trickle charge or while supplying a load. The voltage across some battery packs may approach 1.9V/cell.
The 1.5V of overhead is needed to allow for worst-case
voltage drops across the pass transistor (Q1 of Typical
Q1
R2
R1
2N3904
Powering the MAX712/MAX713
AC-to-DC wall-cube adapters typically consist of a transformer, a full-wave bridge rectifier, and a capacitor.
Figures 10–12 show the characteristics of three consumer product wall cubes. All three exhibit substantial
120Hz output voltage ripple. When choosing an adapter
for use with the MAX712/MAX713, make sure the lowest
wall-cube voltage level during fast charge and full load is
at least 1.5V higher than the maximum battery voltage
while being fast charged. Typically, the voltage on the
D1
DC IN
V+
DRV
MAX712
MAX713
Figure 5. DRV Pin Cascode Connection (for high DC IN voltage
or to reduce MAX712/MAX713 power dissipation in linear mode)
Table 4. MAX712/MAX713 Charge-State Transition Table†
POWER_ON_RESET
UNDER_VOLTAGE
IN_REGULATION
COLD
HOT
0
x
x
x
x
Set trickle
↑
1
x
x
x
No change
↑
x
1
x
x
No change
↑
x
x
0
x
No change
↑
x
x
x
0
No change***
↑
0
0
1
1
Set fast
1
0
0
1
1
No change
1
0
0
↓
1
No change
1
↓
0
1
1
Set fast
1
0
↓
1
1
Set fast
1
0
0
1
↑
No change***
1
0
0
↑
1
Set fast**
1
x
x
0
x
Trickle to fast transition inhibited
1
x
x
x
0
Trickle to fast transition inhibited
1
↑
0
x
x
Set trickle
1
0
↑
x
x
Set trickle
1
x
x
x
↓
Set trickle
RESULT*
† Only two states exist: fast charge and trickle charge.
* Regardless of the status of the other logic lines, a timeout or a voltage-slope detection will set trickle charge.
** If the battery is cold at power-up, the first rising edge on COLD will trigger fast charge; however, a second rising edge will
have no effect.
*** Batteries that are too hot when inserted (or when circuit is powered up) will not enter fast charge until they cool and power is recycled.
_______________________________________________________________________________________
9
MAX712/MAX713
The MAX712/MAX713 can be configured so that voltage
slope and/or battery temperature detects full charge.
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
charge until one of the three fast-charge terminating
conditions is triggered.
If DC IN exceeds 20V, add a cascode connection in
series with the DRV pin as shown in Figure 5 to prevent
exceeding DRV’s absolute maximum ratings.
Select the current-limiting component (R1 or D4) to
pass at least 5mA at the minimum DC IN voltage (see
step 6 in the Getting Started section). The maximum
current into V+ determines power dissipation in the
MAX712/MAX713.
DC IN
V+
REF
DRV
VLIMIT
D1
maximum current into V+ =
(maximum DC IN voltage - 5V)/R1
power dissipation due to shunt regulator =
5V x (maximum current into V+)
CELL_VOLTAGE
GND
CURRENT-SENSE AMPLIFIER
Sink current into the DRV pin also causes power dissipation. Do not allow the total power dissipation to exceed
the specifications shown in the Absolute Maximum
Ratings.
PGM3 FAST_CHARGE Av
BATT-
RSENSE
GND
X
V+
OPEN
REF
BATT-
1
0
0
0
0
8
512
256
128
64
CC
BATT-
BATTIN_REGULATION
1.25V
BATT-
Figure 6. Current and Voltage Regulator (linear mode)
Operating Circuit), the diode (D1), and the sense
resistor (RSENSE). This minimum input voltage requirement is critical, because violating it can inhibit proper
termination of the fast-charge cycle. A safe rule of
thumb is to choose a source that has a minimum input
voltage = 1.5V + (1.9V x the maximum number of cells
to be charged). When the input voltage at DC IN drops
below the 1.5V + (1.9V x number of cells), the part
oscillates between fast charge and trickle charge and
might never completely terminate fast-charge.
The MAX712/MAX713 are inactive without the wall cube
attached, drawing 5µA (max) from the battery. Diode
D1 prevents current conduction into the DRV pin. When
the wall cube is connected, it charges C1 through R1
(see Typical Operating Circuit) or the current-limiting
diode (Figure 19). Once C1 charges to 5V, the internal
shunt regulator sinks current to regulate V+ to 5V, and
fast charge commences. The MAX712/MAX713 fast
10
Fast Charge
C2
The MAX712/MAX713 enter the fast-charge state under
one of the following conditions:
1) Upon application of power (batteries already
installed), with battery current detection (i.e., GND
voltage is less than BATT- voltage), and TEMP
higher than TLO and less than THI and cell voltage
higher than the UVLO voltage.
2) Upon insertion of a battery, with TEMP higher than
TLO and lower than THI and cell voltage higher than
the UVLO voltage.
RSENSE sets the fast-charge current into the battery. In
fast charge, the voltage difference between the BATTand GND pins is regulated to 250mV. DRV current
increases its sink current if this voltage difference falls
below 250mV, and decreases its sink current if the voltage difference exceeds 250mV.
fast-charge current (IFAST) = 0.25V/RSENSE
Trickle Charge
Selecting a fast-charge current (IFAST) of C/2, C, 2C, or
4C ensures a C/16 trickle-charge current. Other fastcharge rates can be used, but the trickle-charge
current will not be exactly C/16.
The MAX712/MAX713 internally set the trickle-charge
current by increasing the current amplifier gain (Figure
6), which adjusts the voltage across R SENSE (see
Trickle-Charge VSENSE in the Electrical Characteristics
table).
______________________________________________________________________________________
NiCd/NiMH Battery
Fast-Charge Controllers
PGM3
FAST-CHARGE
RATE
TRICKLE-CHARGE
CURRENT (ITRICKLE)
V+
4C
IFAST/64
OPEN
2C
IFAST/32
REF
C
IFAST/16
BATT-
C/2
Q1
V+
Configuration:
Typical Operating Circuit
2 x Panasonic P-50AA 500mAh AA NiCd batteries
C/3 fast-charge rate
264-minute timeout
Negative voltage-slope cutoff enabled
Minimum DC IN voltage of 6V
Settings:
Use MAX713
PGM0 = V+, PGM1 = open, PGM2 = BATT-,
PGM3 = BATT-, RSENSE = 1.5Ω (fast-charge current,
IFAST = 167mA), R1 = (6V - 5V)/5mA = 200Ω
Since PGM3 = BATT-, the voltage on RSENSE is regulated to 31.3mV during trickle charge, and the current is
20.7mA. Thus the trickle current is actually C/25, not
C/16.
Further Reduction of Trickle-Charge
Current for NiMH Batteries
The trickle-charge current can be reduced to less than
C/16 using the circuit in Figure 7. In trickle charge,
some of the current will be shunted around the battery,
since Q2 is turned on. Select the value of R7 as follows:
R7 = (VBATT + 0.4V)/(lTRlCKLE - IBATT)
where
V BATT = battery voltage when charged
ITRlCKLE = MAX712/MAX713 trickle-charge
current setting
IBATT = desired battery trickle-charge current
Regulation Loop
The regulation loop controls the output voltage between
the BATT+ and BATT- terminals and the current
through the battery via the voltage between BATT- and
GND. The sink current from DRV is reduced when the
R7
DRV
10k
MAX712
MAX713
BATTERY
Q2
FASTCHG
10k
IFAST/8
Nonstandard Trickle-Charge
Current Example
D1
DC IN
RSENSE
GND
Figure 7. Reduction of Trickle Current for NiMH Batteries
(Linear Mode)
output voltage exceeds the number of cells times
VLIMIT, or when the battery current exceeds the programmed charging current.
For a linear-mode circuit, this loop provides the following
functions:
1) When the charger is powered, the battery can be
removed without interrupting power to the load.
2) If the load is connected as shown in the Typical
Operating Circuit, the battery current is regulated
regardless of the load current (provided the input
power source can supply both).
Voltage Loop
The voltage loop sets the maximum output voltage
between BATT+ and BATT-. If VLIMIT is set to less than
2.5V, then:
Maximum BATT+ voltage (referred to BATT-) = VLIMIT x
(number of cells as determined by PGM0, PGM1)
VLIMIT should be set between 1.9V and 2.5V. If VLIMIT
is set below the maximum cell voltage, proper
termination of the fast-charge cycle might not occur.
Cell voltage can approach 1.9V/cell, under fast charge,
in some battery packs. Tie VLIMIT to VREF for normal
operation.
With the battery removed, the MAX712/MAX713 do not
provide constant current; they regulate BATT+ to the
maximum voltage as determined above.
______________________________________________________________________________________
11
MAX712/MAX713
Table 5. Trickle-Charge Current
Determination from PGM3
The voltage loop is stabilized by the output filter
capacitor. A large filter capacitor is required only if the
load is going to be supplied by the MAX712/MAX713 in
the absence of a battery. In this case, set COUT as:
COUT (in farads) = (50 x ILOAD)/(VOUT x BWVRL)
where BWVRL = loop bandwidth in Hz
(10,000 recommended)
COUT > 10µF
ILOAD = external load current in amps
VOUT = programmed output voltage
(VLIMIT x number of cells)
Current Loop
Figure 6 shows the current-regulation loop for a linearmode circuit. To ensure loop stability, make sure that
the bandwidth of the current regulation loop (BWCRL) is
lower than the pole frequency of transistor Q1 (fB). Set
BWCRL by selecting C2.
BWCRL in Hz = gm/C2, C2 in farads,
gm = 0.0018 Siemens
The pole frequency of the PNP pass transistor, Q1, can
be determined by assuming a single-pole current gain
response. Both fT and Bo should be specified on the
data sheet for the particular transistor used for Q1.
fB in Hz = fT/Bo, fT in Hz, Bo = DC current gain
Condition for Stability of Current-Regulation Loop:
BWCRL < fB
The MAX712/MAX713 dissipate power due to the current-voltage product at DRV. Do not allow the power
dissipation to exceed the specifications shown in the
Absolute Maximum Ratings. DRV power dissipation can
be reduced by using the cascode connection shown in
Figure 5.
Power dissipation due to DRV sink current =
(current into DRV) x (voltage on DRV)
Voltage-Slope Cutoff
The MAX712/MAX713’s internal analog-to-digital converter has 2.5mV of resolution. It determines if the battery voltage is rising, falling, or unchanging by
comparing the battery’s voltage at two different times.
After power-up, a time interval of tA ranging from 21sec
to 168sec passes (see Table 3 and Figure 8), then a
battery voltage measurement is taken. It takes 5ms to
perform a measurement. After the first measurement is
complete, another t A interval passes, and then a
second measurement is taken. The two measurements
are compared, and a decision whether to terminate
charge is made. If charge is not terminated, another full
two-measurement cycle is repeated until charge is
12
terminated. Note that each cycle has two tA intervals
and two voltage measurements.
The MAX712 terminates fast charge when a comparison shows that the battery voltage is unchanging. The
MAX713 terminates when a conversion shows the battery voltage has fallen by at least 2.5mV per cell. This is
the only difference between the MAX712 and MAX713.
Temperature Charge Cutoff
Figure 9a shows how the MAX712/MAX713 detect overand under-temperature battery conditions using negative
temperature coefficient thermistors. Use the same model
thermistor for T1 and T2 so that both have the same
nominal resistance. The voltage at TEMP is 1V (referred
to BATT-) when the battery is at ambient temperature.
The threshold chosen for THI sets the point at which
fast charging terminates. As soon as the voltage-on
TEMP rises above THI, fast charge ends, and does not
restart after TEMP falls below THI.
The threshold chosen for TLO determines the temperature below which fast charging will be inhibited.
If TLO > TEMP when the MAX712/MAX713 start up, fast
charge will not start until TLO goes below TEMP.
The cold temperature charge inhibition can be disabled
by removing R5, T3, and the 0.022μF capacitor; and by
tying TLO to BATT-.
To disable the entire temperature comparator chargecutoff mechanism, remove T1, T2, T3, R3, R4, and R5,
and their associated capacitors, and connect THI to V+
and TLO to BATT-. Also, place a 68kQ resistor from
REF to TEMP, and a 22kΩ resistor from BATT- to TEMP.
COUNTS
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
VOLTAGE
RISES
NEGATIVE
ZERO
VOLTAGE
VOLTAGE
SLOPE
SLOPE
CUTOFF FOR MAX712
CUTOFF FOR MAX712
OR MAX713
ZERO
RESIDUAL
NEGATIVE
RESIDUAL
0
POSITIVE RESIDUAL
5
5
5
5
5
5
tA ms tA ms tA ms tA ms tA ms tA ms
INTERVAL INTERVAL INTERVAL INTERVAL INTERVAL INTERVAL
NOTE: SLOPE PROPORTIONAL TO VBATT
Figure 8. Voltage Slope Detection
______________________________________________________________________________________
t
NiCd/NiMH Battery
Fast-Charge Controllers
REF
R3
THI
T1
HOT
R4
0.022μF
TEMP
+2.0V
AMBIENT
TEMPERATURE
Some battery packs come with a temperature-detecting thermistor connected to the battery pack’s negative
terminal. In this case, use the configuration shown in
Figure 9b. Thermistors T2 and T3 can be replaced by
standard resistors if absolute temperature charge cutoff is acceptable. All resistance values in Figures 9a
and 9b should be chosen in the 10kΩ to 500kΩ range.
__________Applications Information
Battery-Charging Examples
R5
COLD
T2
TLO
MAX712
MAX713
T3
0.022μF
1μF
BATTAMBIENT
TEMPERATURE
NOTE: FOR ABSOLUTE TEMPERATURE CHARGE CUTOFF, T2 AND T3 CAN BE
REPLACED BY STANDARD RESISTORS.
Figures 13 and 14 show the results of charging 3 AA,
1000mAh, NiMH batteries from Gold Peak (part no.
GP1000AAH, GP Batteries (619) 438-2202) at a 1A rate
using the MAX712 and MAX713, respectively. The
Typical Operating Circuit is used with Figure 9a’s
thermistor configuration .
DC IN = Sony AC-190 +9VDC at 800mA AC-DC adapter
PGM0 = V+, PGM1 = REF, PGM2 = REF, PGM3 = REF
R1 = 200Ω, R2 = 150Ω, RSENSE = 0.25Ω
C1 = 1µF, C2 = 0.01µF, C3 = 10µF, VLIMIT = REF
R3 = 10kΩ, R4 = 15kΩ
T1, T2 = part #14A1002 (Alpha Sensors: 858-549-4660) R5
omitted, T3 omitted, TLO = BATT-
Figure 9a. Temperature Comparators
REF
AMBIENT
TEMPERATURE
MAX712/713
11
T2
THI
R5
+2.0V
R3
TEMP
1μF
COLD
OUTPUT VOLTAGE (V)
10
HOT
HIGH PEAK
9
120Hz RIPPLE
8
TLO
0.022μF 0.022μF
MAX712
MAX713
T1
R4
T3
LOW PEAK
7
6
0
BATTIN THERMAL
CONTACT WITH
BATTERY
AMBIENT
TEMPERATURE
200
400
600
800
1000
LOAD CURRENT (mA)
NOTE: FOR ABSOLUTE TEMPERATURE CHARGE CUTOFF, T2 AND T3 CAN BE
REPLACED BY STANDARD RESISTORS.
Figure 9b. Alternative Temperature Comparator Configuration
Figure 10. Sony Radio AC Adapter AC-190 Load Characteristic,
9VDC 800mA
______________________________________________________________________________________
13
MAX712/MAX713
IN THERMAL
CONTACT WITH
BATTERY
Linear-Mode, High Series Cell Count
The absolute maximum voltage rating for the BATT+ pin
is higher when the MAX712/MAX713 are powered on. If
more than 11 cells are used in the battery, the BATT+
input voltage must be limited by external circuitry when
DC IN is not applied (Figure 15).
Efficiency During Discharge
The current-sense resistor, R SENSE, causes a small
efficiency loss during battery use. The efficiency loss is
significant only if R SENSE is much greater than the
10
Status Outputs
Figure 17 shows a circuit that can be used to indicate
charger status with logic levels. Figure 18 shows a
circuit that can be used to drive LEDs for power and
charger status.
16
HIGH PEAK
9
8
120Hz
RIPPLE
7
LOW PEAK
14
HIGH PEAK
12
LOW PEAK
10
6
120Hz
RIPPLE
8
5
400
800
600
LOAD CURRENT (mA)
0
1000
Figure 11. Sony CD Player AC Adapter AC-96N Load
Characteristic, 9VDC 600mA
ΔV
CUTOFF
Δt
4.9
4.8
5.0
38
4.9
36
4.7
34
V
4.6
32
4.5
30
T
4.4
28
34
V
32
30
4.5
T
4.4
28
26
4.3
24
4.2
Figure 13. 3 NiMH Cells Charged with MAX712
36
4.6
26
90
40
38
4.7
4.2
60
30
TIME (MINUTES)
MAX712/713
ΔV
CUTOFF
Δt
4.8
4.3
0
800
Figure 12. Panasonic Modem AC Adapter KX-A11 Load
Characteristic, 12VDC 500mA
40
BATTERY TEMPERATURE (°C)
MAX712/713
5.0
200
600
400
LOAD CURRENT (mA)
24
0
60
30
TIME (MINUTES)
Figure 14. NiMH Cells Charged with MAX713
______________________________________________________________________________________
90
BATTERY TEMPERATURE (°C)
200
BATTERY VOLTAGE (V)
0
14
MAX712/713
18
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
battery stack’s internal resistance. The circuit in Figure
16 can be used to shunt the sense resistor whenever
power is removed from the charger.
MAX712/713
11
BATTERY VOLTAGE (V)
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
NiCd/NiMH Battery
Fast-Charge Controllers
MAX712/MAX713
Q1
D1
DC IN
TO
BATTERY
POSITIVE
TERMINAL
R2
150Ω
OV = NO POWER
5V = POWER
V+
33kΩ
Q2
VCC
MAX712
MAX713
10kΩ
500Ω
OV = FAST
VCC = TRICKLE OR
NO POWER
FASTCHG
DRV
BATT+
MAX712
MAX713
Figure 15. Cascoding to Accommodate High Cell Counts for
Linear-Mode Circuits
Figure 17. Logic-Level Status Outputs
DC IN
D1
R1
>4 CELLS
MAX712
MAX713
CHARGE POWER
100kΩ
V+
*
100kΩ
RSENSE
V+
* LOW RON
LOGIC LEVEL
N-CHANNEL
POWER
MOSFET
GND
Figure 16. Shunting RSENSE for Efficiency Improvement
470ΩMIN
MAX712
MAX713
FAST CHARGE
FASTCHG
Figure 18. LED Connection for Status Outputs
______________________________________________________________________________________
15
MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
Ordering Information (continued)
PART
TEMP RANGE
___________________Chip Topography
PIN-PACKAGE
MAX713CPE
0°C to +70°C
16 Plastic DIP
MAX713CSE
MAX713C/D
MAX713EPE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
16 Narrow SO
Dice*
16 Plastic DIP
MAX713ESE
MAX713MJE
-40°C to +85°C
-55°C to +125°C
16 Narrow SO
16 CERDIP**
BATT+
VLIMIT
REF
V+
DRV
PGM0
PGM1
*Contact factory for dice specifications.
**Contact factory for availability and processing to MIL-STD-883.
GND
Package Information
0.126
(3.200mm)
(For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages.)
BATT-
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
16 Plastic DIP
P16-1
21-0043
16 Narrow SO
S16-1
21-0041
16 CERDIP
J16-3
21-0045
THI
CC
TLO
PGM3
TEMP
FASTCHG
PGM2
0.80"
(2.032mm)
TRANSISTOR COUNT: 2193
SUBSTRATE CONNECTED TO V+
16
______________________________________________________________________________________
NiCd/NiMH Battery
Fast-Charge Controllers
REVISION
NUMBER
REVISION
DATE
6
12/08
DESCRIPTION
Removed switch mode power control and added missing package
information
PAGES
CHANGED
1, 5, 6, 9, 10, 12,
13, 14, 16, 17
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX712/MAX713
Revision History
MAX713 Switch-Mode Evaluation Kit
______________Ordering Information
PART
MAX713SWEVKIT-SO
TEMP. RANGE
0°C to +70°C
BOARD TYPE
Surface Mount
____________________Component List
DESIGNATION QTY
C1
1
C2
1
C3, C5, C6
3
C4
1
D1, D2
2
D3
1
D4
1
J1, J2
2
L1
1
M1
1
Q1, Q3, Q4
3
Q2
1
R1, R6
R2
0
1
R3
1
R4
R5
R7
R8
U1
None
None
1
1
1
1
1
1
1
DESCRIPTION
1µF, 25V capacitor
Sprague 595D105X0025A
220pF, 50V capacitor
10µF, 50V capacitors
Sprague 595D106X0050R
0.1µF, 50V capacitor
3A, 40V Schottky diodes
Motorola MBRS340T3
Red LED
8.2mA, 50V current-limiting diode
Central Semiconductor CCLHM080
2-pin power connectors
220µH, 1.5A inductor
CoilCraft DO3340-224
0.3Ω, 50V P-channel MOSFET
International Rectifier IRFR9024
50V NPN transistors
Central Semiconductor CMPTA06 or
Motorola MMBTA06LT1
50V PNP transistor
Central Semiconductor CMPT2907A or
Motorola MMBT2907ALT1
Reserved for optional resistors
5.1kΩ, 5% resistor
0.25Ω, 1/2W resistor
Dale WSL-2512-R250-J or
IRC LR2010-01-R250-K
1.5kΩ, 5% resistor
470Ω, 5% resistor
68kΩ, 5% resistor
22kΩ, 5% resistor
Maxim MAX713CSE IC
MAX712/MAX713 data sheet
3.0" x 3.0" printed circuit board
____________________________Features
♦ Up to 1A Charge Current
♦ 45V Peak Input Voltage Range
♦ Switch-Mode Operation Reduces Heat Dissipation
♦ Surface-Mount Components
♦ Charges 1 to 16 Series Cells
______________Component Suppliers
SUPPLIER
PHONE
FAX
Tantalum Capacitors
AVX
Sprague
(207) 282-5111
(603) 224-1961
(207) 283-1941
(603) 224-1430
Low-Value Resistors
Dale-Vishay
IRC
(402) 564-3131
(512) 992-7900
(402) 563-1841
(512) 992-3377
High-Current Inductor
CoilCraft
(708) 241-7876
(708) 639-1469
(516) 435-1110
(516) 435-1824
(310) 322-3331
(310) 322-3332
(602) 244-3576
(805) 867-2555
81-3-3494-7411
(602) 244-4015
(805) 867-2556
81-3-3494-7414
Semiconductors
Central
Semiconductor
International
Rectifier
Motorola
Nihon: USA
Nihon: Japan
Please indicate that you are using these parts with the MAX713
when contacting the above vendors.
______________________________EV Kit
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
1
Evaluates: MAX712/MAX713
_______________General Description
The MAX713SWEVKIT-SO is a fully assembled and tested
surface-mount board. The MAX713 high-current, switchmode battery charger controls a P-channel power MOSFET, allowing charge currents up to 1A. Switch-mode
operation typically provides 75%-efficient conversion,
reducing heat compared to linear-regulator solutions.
The MAX713SWEVKIT can also be used to evaluate the
MAX712 just by replacing the MAX713CSE with a
MAX712CSE.
Evaluates: MAX712/7MAX13
MAX713 Switch-Mode Evaluation Kit
_________________________Quick Start
The MAX713 Switch-Mode EV kit is a fully assembled
and tested surface-mount board. Follow these steps to
verify board operation. Do not turn on the power until
all connections are completed.
1) Set the charging parameters to match the charge
current and number of cells of the battery being
charged. Refer to the section Setting the Charging
Parameters and to the MAX712/MAX713 data sheet
for instructions. The board is shipped configured for
six cells and 1A of charge current.
2) Connect the input power source (14V to 16V, 1.3A
as configured) to the 2-pin power connector.
Observe the polarity indicated next to the connector. The input supply must be 2V greater than the
maximum battery charging voltage, and capable of
providing the charge current.
3) Connect the battery to the 2-pin battery terminal.
Observe the polarity markings.
4) Turn on the power to the board and use a DVM to
confirm the voltage across the battery and the
sense resistor.
_______________Detailed Description
Input Supply Range
The input power supply must be at least 2V greater than
the peak battery voltage. The upper limit is determined
by the breakdown voltage of the P-channel power MOSFET and the capacitors across the input supply. When
choosing an adapter for use with the MAX712/MAX713
switch-mode circuit, make sure that the lowest wall-cube
voltage level during fast charge and full load is a least 2V
higher than the maximum battery voltage while being fast
charged. Typically, the voltage on the battery pack is
higher during a fast-charge cycle than while in trickle
charge or while supplying a load. The voltage across
some battery packs may approach 1.9V/cell. This minimum input voltage requirement is critical, because its
violation may inhibit proper termination of the fast-charge
cycle. A safe rule of thumb is to choose a source that
has a minimum input voltage = 2V + (1.9V x the maximum number of cells to be charged).
The components included in this kit are rated at 50V, so
the input source must never exceed 50V. Depending
on your application, you can substitute capacitors and
other components with different ratings.
The EV kit is shipped with all programming inputs
(PGM0-PGM3) open. This sets the MAX713 for six cells,
1A of charging current, 45 minutes maximum charge
2
time, and 42 seconds between battery voltage measurements. The default conditions require an input
source greater than 14V and capable of greater than
1.3A. Be sure to read the section titled Setting the
Charging Parameters before connecting any battery.
A current-limiting diode (D4) on the EV kit allows a wide
input voltage range. This diode provides a fixed 8mA of
current to the MAX713 shunt regulator. For applications
with a narrow input voltage range, you can replace the
diode with a resistor selected for the same current flow
between the input source and the V+ pin.
Setting the Charging Parameters
For each battery type connected, the EV kit must be set
for the proper number of cells, the proper maximum
charging time and sampling intervals, and the proper
charging current. Select the number of cells by connecting the PGM0 and PGM1 pins per Table 1. Whenever
changing the number of cells to be charged, PGM0 and
PGM1 need to be adjusted accordingly. Attempting to
charge more or fewer cells than the number programmed may disable the voltage-slope fast-charge termination circuitry.
The EV kit is shipped with PGM0 and PGM1 open, which
sets the number of cells at six. You can alter the programmed number of cells by installing jumper wires
across the holes provided on the board. For example, to
configure the board for four cells, solder wires between
pins 1 & 4 of SW1 (PGM0) and pins 1 & 2 of SW2 (PGM1).
Table 1. Programming the Number of Cells
NUMBER
PGM0
SW1
PGM1
SW2
OF CELLS CONNECTION JUMPER CONNECTION JUMPER
1
V+
1–4
V+
2
V+
1–4
Open
—
3
V+
1–4
REF
1–3
4
V+
1–4
BATT-
1–2
5
Open
—
V+
1–4
6
Open
—
Open
—
7
Open
—
REF
1–3
8
Open
—
BATT-
1–2
9
REF
1–3
V+
1–4
10
REF
1–3
Open
—
11
REF
1–3
REF
1–3
12
REF
1–3
BATT-
1–2
13
BATT-
1–2
V+
1–4
14
BATT-
1–2
Open
—
15
BATT-
1–2
REF
1–3
16
BATT-
1–2
BATT-
1–2
_______________________________________________________________________________________
1–4
MAX713 Switch-Mode Evaluation Kit
D3
LED
RED
R1
OPEN
R2
5.1k
1
Q1
CMPTA06
1
2
2
Q2
2N2907
1
JU1
JUMPER
1
Q3
CMPTA06
1
2
3
3
JU2
CUT HERE
2
R4
1.5k
11
14
5
REF
4
3
2
SW1
4
3
2
SW2
SW3
4
3
2
SW4
R5 470Ω
15
1
4
3
2
3
4
1
1
DRV
C2
220pF
CC
THI
V+
U1
BATT+
BATT–
TLO
12
6
1 VLIMIT
R6
OPEN
16 REF
1
C4
0.1µF
R8
22k
GND
7
C3
10µF
50V
MAX713
9 PGM2
REF
BATT+
2
PGM0
PGM1
10 PGM3
R7
68k
C1
1µF
10V
220µH
D1
D2
MBRS340T3 MBRS340T3
3
D4
CCLHM080
(8mA CURRENTLIMITING DIODE)
3
Q4
CMPTA06
2
C6
10µF
50V
C5
10µF
50V
Evaluates: MAX712/MAX713
FAST CHARGE
L1
DO3340
M1
IRFR9024
DCIN
R3
0.25Ω
CURRENTSENSE
RESISTOR
BATT-
13
GND
TEMP
FASTCHG
8
Figure 1. MAX713 Switch-Mode EV Kit Schematic
Table 2. Programming the Timing Functions
TIMEOUT
(MINUTES)
22
22
33
33
45
45
66
66
90
90
132
132
180
180
264
264
SAMPLE
INTERVAL
(SECONDS)
21
21
21
21
42
42
42
42
84
84
84
84
168
168
168
168
SLOPE
LIMIT
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
TRICKLE
VOLTAGE
(mV)
4
4
4
4
8
8
8
8
16
16
16
16
32
32
32
32
PGM2
CONNECTION
SW3
JUMPER
PGM3
CONNECTION
SW4
JUMPER
Open
REF
V+
BATTOpen
REF
V+
BATTOpen
REF
V+
BATTOpen
REF
V+
BATT-
—
1–3
1–4
1–2
—
1–3
1–4
1–2
—
1–3
1–4
1–2
—
1–3
1–4
1–2
V+
V+
V+
V+
Open
Open
Open
Open
REF
REF
REF
REF
BATTBATTBATTBATT-
1–4
1–4
1–4
1–4
—
—
—
—
1–3
1–3
1–3
1–3
1–2
1–2
1–2
1–2
_______________________________________________________________________________________
3
Evaluates: MAX712/MAX713
MAX713 Switch-Mode Evaluation Kit
This jumper configuration connects PGM0 to V+ and
PGM1 to BATT-.
Select the maximum charging time and the time interval
between cell voltage readings for delta-slope termination
by connecting the PGM2 and PGM3 pins per Table 2.
Refer to the MAX712/MAX713 data sheet for detailed
information on the operation of these pins.
The charge current is determined by the value of the
current-sense resistor (R3) and the fixed 250mV across
the resistor during fast-charge. To change the charge
current, calculate the new current-sense resistor value
and install that value in the position provided (R8), then
remove the factory-installed R3. Choose RSENSE using
the following formula:
RSENSE = 0.25V/IFAST
See the MAX712/MAX713 data sheet for detailed information on setting the fast-charge and trickle-charge currents.
Transistors Q1 and Q2 provide a low-impedance drive
to the gate. If the DCIN voltage is less than 15V, the
MAX713 DRV pin can be directly connected to Q1 and
Q2. For DCIN voltages greater than 15V, a transistor
level shifter (Q3, R4) is inserted to provide the proper
voltage swing to Q1 and Q2. Q3 is mounted on the
evaluation board, but it is not used in the standard configuration. If Q3 is needed, then cut the trace across
JU2 and solder a jumper across JU1.
Inductor Selection
The inductor value is not critical to circuit operation.
However, the greater its value, the lower the output ripple
current. The CoilCraft inductor used on the evaluation
board was chosen because it is the highest value (220µH)
surface-mount inductor with a 1.5A rating currently available. Larger inductors, such as toroids, may be used for
lower output ripple current or higher current-charge rates.
Gate-Drive Current
The voltage swing on the gate of the power MOSFET
(M1) must be greater than 8V and less than 15V.
Figure 2. MAX713 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX713 EV Kit PC Board Layout—Component Side
Figure 4. MAX713 EV Kit PC Board Layout—Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1995 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
Maxim > App Notes > Battery Management Power-Supply Circuits Keywords: switchmode battery chargers, NiMH/NiCd battery chargers, stepdown regulators, constant-current supplies, dV/dt termination
Aug 09, 2010
APPLICATION NOTE 4496
NiMH/NiCd Switchmode Battery Charger Has dV/dt Charge
Termination
Abstract: This circuit includes a battery charger (MAX712) and step-down switching regulator (MAX5089) for handling the power
portion of the charger. By controlling the regulator the MAX712 acts as a battery-charge controller, producing outputs of 7V to
16V. It operates from any DC source capable of delivering the desired fast-charge current, with this condition: the output voltage
must equal 1.7V multiplied by the sum of (two plus the number of batteries to be charged in series).
A similar version of this article appeared in the December 17, 2008 issue of Portable Design magazine.
All battery chargers can be regarded as constant-current power supplies, but they differ from power supplies in two important
respects: battery chargers (by design) block all discharge paths from battery to charger, under any conditions. They also include
circuitry that decides when the battery has taken a full charge (signaling when the full-charge current must be reduced), and when
the charging process should be terminated.
Several techniques are available for deciding when a NiCd or NiMh battery is fully charged. The most common of these relies on
terminating the charge when the battery terminals reach a particular voltage level, based on a characteristic increase in the positive
slope of voltage versus time.
This is not the best method, because the absolute value of termination voltage depends strongly on the ambient temperature and
the charge rate (the "C" rate). The final result can therefore be an under- or over-charged battery. Overcharging a NiCd or NiMh
battery is not as serious as for lithium batteries, which are much more sensitive to damage. NiCd and NiMh batteries are more
rugged devices. Undercharging is a problem, simply because the store of charge will be less than expected.
Most of the better termination methods rely on the fact that charging transforms electrical energy into stored (potential) chemical
energy. Charging is an endothermic process. That means the battery temperature not only doesn't rise; it actually falls slightly
during a charge.
When a battery reaches full charge, the reactions that transform electrical energy to chemical energy cease. Any further electrical
energy forced into the battery by the charger transforms to heat, which increases the battery temperature. At that point charging
should stop, because the battery has stored 100% of its capacity.
You can sense this temperature increase and use it as a signal for termination of charging, but that measurement implies a thermal
sensor in intimate contact with the battery—not always a feasible arrangement. You can also sense the temperature increase by
changes in the battery's terminal voltage, which is a sensitive indicator of internal temperature changes. Thus, charging a battery
produces a positive slope in the plot of voltage versus time. The positive slope turns negative when a NiCd battery reaches full
charge, and goes to zero (flat) when a NiMh battery reaches full charge.
Figure 1 shows the terminal voltage vs. time for a NiCd battery under charge. The time scale for change of slope, which can
range from minutes to tens of minutes according to the battery size, depends on the thermal time constant of the battery and its
enclosure. It also depends on the charge rate (i.e., the charging current), because the temperature increase and its rate of increase
are functions of the battery's thermal capacity and of power delivered (which, in turn, is a function of charging current).
Page 1 of 3
Figure 1. These curves show the voltage and temperature characteristics of a NiCd cell as it approaches and passes the fully
charged condition.
To detect slope changes, the charge controller must run a detection algorithm that makes sequenced voltage measurements at
long time intervals and then stores the results for comparison. This capability, which cannot be implemented in analog form, must
be performed by a combination of ADC, memory, timer, and sequencer.
IC battery chargers such as the MAX712 (for NiMh batteries) and MAX713 (for NiCd batteries) run dV/dt slope-sensing chargetermination algorithms. The power section of these devices is linear and has limited efficiency, but is adequate for smaller-capacity
batteries.
The circuit of Figure 2 includes a MAX712 or MAX713 battery charger, and also a switching regulator (MAX5089) that handles the
power portion of the charger. This regulator operates at higher efficiency and a higher switching frequency (2MHz), which in turn
enables construction of smaller-size chargers capable of higher fast-charge rates, yet with little need for heat-sinking.
Figure 2. This switchmode charger for NiCd and NiMh batteries uses their dV/dt behavior as an indicator for charge termination.
Page 2 of 3
The MAX5089 step-down regulator is controlled by the MAX712 or MAX713, acting as a battery-charge controller. It produces
outputs of 7V to 16V and operates from any DC source capable of delivering the desired fast-charge current, with this condition:
the output voltage must equal 1.7V multiplied by the sum of (two plus the number of batteries to be charged in series).
The Figure 2 circuit charges a pack of 1 to 8 cells with fast-charge currents as high as 2.5A, and retains all programmable features
described in the MAX712/MAX713 data sheets. When charging is complete, the MAX712/MAX713 devices go to a state called
"trickle charge," in which they inject a small fraction of the full charge current (to compensate for the self-discharge always
present). You can therefore leave the battery connected to the charger, and find it charged to +100% when needed. Data sheets
for the MAX712/MAX713 and MAX5089 are available at www.maxim-ic.com.
Related Parts
MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch -- Free Samples
MAX712
NiCd/NiMH Battery Fast-Charge Controllers
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Page 3 of 3
Maxim > Design support > App notes > Battery Management > APP 680
Maxim > Design support > App notes > Power-Supply Circuits > APP 680
Keywords: linear, switch-mode, battery charger, microcontroller, current source, switching dc-dc converter, notebook computer,
lithium-ion, Li+, lithium, 8051, NiCd, NiMH, Nickel Metal Hydride, Microchip PIC, voltage regulator, current regulators
APPLICATION NOTE 680
Jul 22, 2002
How to Design Battery Charger Applications that Require External
Microcontrollers and Related System-Level Issues
Abstract: Notebook computers increasingly require complex battery charging algorithms and systems. This article provides information
and background on lithium-ion (Li+), nickel-cadmium (NiCd), and nickel-metal-hydride (NiMH) batteries and related system-level
switch-mode and linear battery chargers. These voltage regulators and current regulators are controlled by external microprocessors
like the 8051 or Microchip PIC, and examples are provided with these controllers. An overview of requirements for charging common
battery chemistries with Maxim battery charger ICs is provided, along with a discussion of system-level trade-offs and firmware
design tips, and a list of World Wide Web engineering resources.
The previous issue of Maxim's Engineering Journal (Vol. 27) discussed new developments in stand-alone battery chargers. This
second article of a two-part series explores the system-level issues in applying battery-charger ICs.
Over the past five years, market pressures on portable equipment have transformed the simple battery charger into a sophisticated
switch-mode device capable of charging an advanced battery in 30 minutes. This development also marks a departure from the selfcontained, stand-alone charger ICs of only a few years ago. Some of those ICs included considerable intelligence: enough to handle
the complex task of fast charging advanced batteries.
Maxim still manufactures stand-alone charger ICs, but market demand has changed recently. Today's battery-charger subsystems
regulate charging voltage and current using the intelligence of an external microcontroller (µC), usually available elsewhere in the
system. This approach achieves low cost in high-volume applications and allows the greatest flexibility in tailoring the charger to a
specific application.
All necessary intelligence once resided in the battery-charger controller IC itself, but now the system designer must implement a
charging algorithm and write the associated firmware. This article provides the information and background necessary to implement
charger systems based on Maxim's wide range of battery-charger ICs for all popular chemistries.
The following discussion presents an overview of the requirements for charging common battery chemistries with Maxim batterycharger ICs. It addresses system-level trade-offs and firmware design tips, and lists World Wide Web resources available to
designers. The discussion closes with design examples based on two common µCs: the 8051 and the Microchip PIC. Either example
can serve as a base for further development of custom charger circuitry.
Overview of Battery-Charging Techniques
Four rechargeable battery chemistries are in practical use today: nickel cadmium (NiCd), nickel metal hydride (NiMH), gelled leadacid (PbSO4), and lithium-ion (Li+). The trade-offs to be made among these chemistries are beyond the scope of this article, but the
References section provides access to such information.
Caution: consult the battery manufacturer for specific recommendations. The information presented here is
intended only as an overview of charging requirements for various cell chemistries.
This section describes general charging techniques and limitations for the four common chemistries. For additional details and
background, see the Maxim data sheets and other reference material cited at the end of the article.
Fast battery charging has several phases, as explained in the text and by the state diagram for a generic charger (Figure 1).
Page 1 of 13
Figure 1. Generic charger-state diagram.
Initialization
Though not a part of the actual charging procedure, initialization is an important stage in the process. The charger initializes itself
and performs its own self-test. A charge can be interrupted by a power failure and consequent reinitialization. Without a smart battery
or some type of time-stamped, nonvolatile storage, such events can occur unnoticed. Most chargers reinitialize themselves fully after
a power failure. If overcharging is an issue, the charger can then execute a special self-test sequence to determine if the battery is
already charged. A battery present on power-up, for example, should trigger such an action.
Several circumstances can allow this initialization to cause charging problems. A fixed-time charger, for example, applies charge to a
battery for a fixed interval of four hours. If a power failure occurs three hours and 59 minutes into the charge, the charger starts
another four-hour charge, giving the battery a four-hour overcharge. This treatment can damage the battery, and it is one reason
fixed-time charging is seldom used. The example also shows why the charger should monitor battery temperature or use other
termination methods as a backup measure.
Cell Qualification
This phase of the charging procedure detects when a battery is installed and whether it can be charged. Cell detection is usually
accomplished by looking for voltage on the charger terminals while the charger source is off, but that method can pose a problem if
the cells have been deeply cycled and are producing little voltage. As an alternative, the charger often looks for a thermistor or
shorting jumper rather than the cell itself. The presence of this hardware can also serve to identify the battery pack. Smart batteries,
on the other hand, conduct a rich exchange of serial data with the battery pack, usually providing all the necessary charging
parameters over a specialized I²C-like protocol called the System Management Bus (SMBus™).
Page 2 of 13
Once the charger determines that a cell is installed, it must determine if the cell is good. During this subphase (qualification), the cell
is checked for basic functioning: open, shorted, hot, or cold. To test whether or not a cell is chargeable, some chargers-lead-acid
types especially-apply a light charging current (about one-fifth of the fast rate) and allow the cell a fixed amount of time to reach a
specified voltage. This technique avoids the problem of false rejects for deeply cycled PbSO4 batteries, and with the battery
manufacturer's approval, it can be used for other chemistries as well.
A check of the ambient and cell temperatures is also a part of the qualification phase. When a charger detects high or low
temperature, it usually waits a predetermined interval for the temperature to return to nominal. If this doesn't happen within the
allotted time, the charger reduces the charging current. This action in turn reduces battery temperature, which increases efficiency.
Finally, the cells are checked for opens and shorts. Open cells are easily detected, but a shorted-cell indication requires confirmation
in order to avoid false failure indications. If all of these checks are satisfactory, the cell can be charged, and the state is advanced as
shown in Figure 1.
Preconditioning Phase (Optional)
Some chargers (primarily those for NiCd batteries) include an optional preconditioning phase in which the battery is fully discharged
before recharging. Full discharge reduces each battery's voltage level to 1V per cell and eliminates dendritic formations in the
electrolyte, which cause what is often falsely labeled the memory effect. This so-called memory effect refers to the presence of
dendritic formations that can reduce the run life of a cell, but a complete charge and discharge cycle sometimes eliminates the
problem.
Preconditioning can be accomplished before each charge, or it can follow an indication (by load test or other operation) that more
than half of the cell's charge remains. Preconditioning can last from one to ten hours. Discharging a battery in less than one hour is
not generally recommended. Fast preconditioning raises the practical problem of what to do with heat dissipated by the load resistor.
Nor is preconditioning for longer than ten hours usually recommended unless it can be initiated manually upon detection of reduced
capacity. Confusion and misunderstanding surround the NiCd "memory effect," so the designer should avoid putting a button on the
charger to counteract it.
Fast-Charge Phase and Termination
Fast-charge and termination methods used depend on cell chemistry and other design factors. The following discussion covers fastcharging techniques widely used for today's common battery chemistries. For specific guidelines and recommendations, consult the
battery manufacturer's applications department.
NiCd and NiMH Cells
Fast-charging procedures for NiCd and NiMH batteries are very similar; they differ primarily in the termination method used. In each
case, the charger applies a constant current while monitoring battery voltage and other variables to determine when to terminate the
charge. Fast-charge rates in excess of 2C are possible, but the most common rate is about C/2. Because charging efficiency is
somewhat less than 100%, a full charge at the C/2 rate requires slightly more than two hours.
While constant current is applied, the cell voltage rises slowly and eventually reaches a peak (a point of zero slope). NiMH charging
should be terminated at this peak (the 0ΔV point). NiCd charging, on the other hand, should terminate at a point past the peak:
when the battery voltage first shows a slight decline (-ΔV) (Figure 2). Cell damage can result if fast charge continues past either
battery's termination point.
Page 3 of 13
Figure 2. NiCd battery-charging characteristics at C/2 rate.
At rates exceeding C/2 (resulting in a charge time of no more than two hours), the charger also monitors the cell's temperature and
voltage. Because cell temperature rises rapidly when a cell reaches full charge, the temperature monitor enables another termination
technique. Termination on this positive temperature slope is called ΔT termination. Other factors that can trigger termination include
charging time and maximum cell voltage. Well-designed chargers rely on a combination of these factors.
Note: Because certain effects that appear when a cell first begins charging can imitate termination conditions, chargers usually
introduce a delay of one to five minutes before activating slope-detection termination modes. Also, charge-termination conditions are
difficult to detect for rates below C/8, because the voltage and temperature slopes of interest (ΔV/Δt and ΔT/Δt) are small and
comparable to other system effects. For safety during a fast charge, the hardware and software in these systems should always err
on the side of earlytermination.
Lithium-Ion Cells
Li+ battery charging differs from the nickel-chemistry charging schemes. A top-off charge can follow to ensure maximum energy
storage in a safe manner. Li+ chargers regulate their charging voltage to an accuracy better than 0.75%, and their maximum
charging rate is set with a current limit, much like that of a bench power supply (Figure 3). When fast charging begins, the cell
voltage is low, and charging current assumes the current-limit value.
Figure 3. Li+ battery voltage vs. charging current.
Battery voltage rises slowly during the charge. Eventually, the current tapers down, and the voltage rises to a float-voltage level of
4.2V per cell (Figure 4).
Page 4 of 13
Figure 4. Li+ battery-charging profile.
The charger can terminate charging when the battery reaches its float voltage, but that approach neglects the topping-off operation.
One variation is to start a timer when float voltage is reached, and then terminate charging after a fixed delay. Another method is to
monitor the charging current, and terminate at a low level (typically 5% of the limit value; some manufacturers recommend a higher
minimum of 100mA). A top-off cycle often follows this technique, as well.
The past few years have yielded improvements in Li+ batteries, the chargers, and our understanding of this battery chemistry. The
earliest Li+ batteries for consumer applications had shortcomings that affected safety, but those problems cannot occur in today's
well-designed systems. Manufacturers' recommendations are neither static nor totally consistent, and Li+ batteries continue to evolve.
Lead-Acid Cells
PbSO4 batteries are usually charged either by the current-limited method or by the more common and generally simpler voltagelimited method. The voltage-limited charging method is similar to that used for Li+ cells, but high precision isn't as critical. It requires
a current-limited voltage source set at a level somewhat higher than the cell's float voltage (about 2.45V).
After a preconditioning operation that ensures that the battery will take a charge, the charger begins the fast charge and continues
until it reaches a minimum charging current. (This procedure is similar to that of a Li+ charger). Fast charge is then terminated, and
the charger applies a maintenance charge of VFLOAT (usually about 2.2V). PbSO4 cells allow this float-voltage maintenance for
indefinite periods (Figure 5).
Figure 5. PbSO4 battery-charging profile.
At higher temperatures, the fast-charge current for PbSO4 batteries should be reduced according to the typical temperature
coefficient of 0.3% per degree centigrade. The maximum temperature recommended for fast charging is about 50°C, but
maintenance charging can generally proceed above that temperature.
Page 5 of 13
Optional Top-Off Charge (All Chemistries)
Chargers for all chemistries often include an optional top-off phase. This phase occurs after fast-charge termination and applies a
moderate charging current that boosts the battery up to its full-charge level. (The operation is analogous to topping off a car's gas
tank after the pump has stopped automatically.) The top-off charge is terminated on reaching a limit with respect to cell voltage,
temperature, or time. In some cases, top-off charge can provide a run life of 5% or even 10% above that of a standard fast charge.
Extra care is advisable here: the battery is at or near full charge and is therefore subject to damage from overcharging.
Optional Trickle Charge (All Chemistries Except Li+)
Chargers for all chemistries often include an optional trickle-charge phase. This phase compensates for self-discharge in a battery.
PbSO4 batteries have the highest rate of self-discharge (a few percent per day), and Li+ cells have the lowest. The Li+ rate is so
low that trickle charging is not required or recommended. NiCds, however, can usually accept a C/16 trickle charge indefinitely. For
NiMH cells, a safe continuous current is usually around C/50, but trickle charging for NiMH cells is not universally recommended.
Pulsed trickle is a variation in which the charger provides brief pulses of approximately C/8 magnitude, with a low duty cycle that
provides a typical average trickle current of C/512. Because pulsed-trickle charging applies to both nickel chemistries and lends itself
well to the on/off type of microprocessor (µP) control, it is used almost universally.
Generic Charging System
Before looking at specific circuit implementations, designers should become familiar with generic blocks and features (Figure 6). All
fast chargers should include these block functions in some form. The bulk power source provides raw dc power, usually from a wall
cube or brick. The current and voltage controls regulate current and voltage applied to the battery. For less-expensive chargers, the
regulator is usually a power transistor or other linear-pass element that dissipates power as heat. It can also be a buck switching
supply that includes a standard freewheeling diode for average efficiency or a synchronous rectifier for highest efficiency.
Figure 6. Generic charging-system block diagram.
The blocks on the right in Figure 6 represent various measurement and control functions. An analog current-control loop limits the
maximum current delivered to the battery, and a voltage loop maintains a constant voltage on the cell. (Note that Li+ cells require a
high level of precision in the applied charging voltage.)
A charger's current-voltage (I-V) characteristic can be fully programmable, or it can be programmable in current only, with a voltage
limit (or vice versa). Cell temperature is always measured, and charge termination can be based either on the level or the slope of
this measurement. Chargers also measure charging time, usually as a calculation in the intelligence block.
Page 6 of 13
This block provides intelligence for the system and implements the state machine previously described. It knows how and when to
terminate a fast charge. Intelligence is internal to the chip in stand-alone charger ICs. Otherwise, it resides in a host µC, and the
other hardware blocks reside in the charger IC. As mentioned previously, this latter architecture is the one preferred today.
Overview of Maxim's Charger Offerings
Maxim manufactures a broad selection of stand-alone and controller-type battery-charger ICs. The variety enables a system
designer to make tradeoffs in performance, features, and cost. Table 1 lists these ICs by the battery chemistry supported, in their
order of introduction, with the most recent models at the top.
Table 1. Overview of Maxim's
Standard
Control
Part
Regulation
Method
Mode**
µC
Synchronous
MAX1647 control,
switching
SMBus
Synchronous
MAX1648 User
switching
DAC or
Synchronous
MAX745 standswitching
alone
DAC or
MAX846A standLinear
alone
DAC or
Synchronous
MAX1540 standswitching
alone
Battery-Charger ICs
Features
Chemistry
Smart-battery system, level 2 compliant, smartbattery charger with SMBus, Li+, independent I- All
V control
Analog-controlled version of MAX1647, highAll
accuracy switching, I/V source: Li+
Advanced, low-cost, switch-mode Li+ charger,
stand-alone, Li+ only
Li+
Low-cost, universal charger, accurate reference
for Li+, external CPU support, reset and
All
regulator
Analog-controlled, switch-mode current source,
Li+ or universal
Li+, NiCd,
NiMH
Charge
Rate
Charge
Termination
Method
Programmed Programmed
Programmed Programmed
Constant
voltage, Li+
Constant
voltage, Li+,
programmed
Fast, trickle,
pulse-trickle,
top-off
MAX712
Standalone
Linear
Complete, low-cost NiMH with termination
modes, max times, LED outputs. No Li+.
NiMH
Fast, trickle
MAX713
Standalone
Linear
Complete, low-cost NiCd with termination
modes, max times, LED outputs. No Li+.
NiCd
Fast, trickle
Li+ float
Li+ float or
programmed
Programmed or
Li+ stand-alone
0ΔV, max voltage,
max temperature,
max time
0ΔV, max voltage,
max temperature
max time
*The use of a DAC and µC is also possible with the DAC-input types.
**All linear types can be used in a hysteretic switching mode for higher efficiency.
The choice between linear and switch-mode regulation constitutes a major design decision. Linear mode is less costly, but it
dissipates power and gets hot. Heat may not be a problem in large desktop chargers, but it can be unacceptable in smaller systems
such as a notebook PC. Synchronous switching regulators offer the highest efficiency (in the mid-90% range), which makes them
suitable for the smallest systems, including cell phones. Some of the nonsynchronous switch-mode circuits listed also offer
reasonable efficiency. In addition, most of the linear parts can be used in a moderately efficient hysteretic switching mode. (For
details, consult the appropriate data sheet.)
The charger's level of autonomy poses another design decision. Stand-alone chargers, for example, are completely self-contained.
The MAX712/MAX713 have LED-control outputs for the user's end equipment as well.
Other devices can stand alone or can operate with a digital-to-analog converter (DAC) and µP. They include the
MAX1640/MAX1641, MAX846A, and MAX745. The MAX1640, a voltage-limited current source intended primarily for charging nickelchemistry batteries, includes a charge timer and pulse-trickle circuitry. It has stand-alone features and operates with a high-efficiency
synchronous switching regulator or (for lower cost applications) a standard switcher.
The MAX846A and MAX745 are both capable of stand-alone operation in charging Li+ batteries, and they include the high-accuracy
reference and independent voltage and current control necessary for universal controllers. The MAX846A is a linear type, and the
MAX745 is a synchronous-switching type. Though either can stand alone, they usually operate with a µC that provides limited control
of the charging process. LED illumination and fast-charge termination are usually initiated by the software. The MAX846A includes a
linear regulator and a CPU-reset output for the µC.
Page 7 of 13
The least autonomous and most flexible devices are the MAX1647 and MAX1648. They are similar, except the MAX1647 has built-in
DACs and an SMBus serial port, and the MAX1648 has analog inputs for voltage and current control. The MAX1647 is a complete,
serially controlled dc power supply with independent voltage and current registers. Capable of SMBus communications with a smart
battery, it provides Level 2 compliance with the Intel/Duracell smart-battery specification.
µC Design Tips
These charger ICs typically operate with a low-cost 8-bit controller such as the 8051, PIC, 68HC11, or 68HC05. The firmware can
be written in assembly language or in C, either of which feature ready availability, low cost, and free tools. Third parties and
manufacturers of these devices have assembled an impressive array of compilers, assemblers, emulators, and code libraries. Much
of this source code is available on the World Wide Web, especially the toolbox routines for assembly language. The Tips for charger
program structure section provides further information on these resources.
All common 8-bit µCs are suitable, but the selection of a specific µC is beyond the scope of this article. Peripherals such as analogto-digital converters (ADCs), DACs, and the SMBus serial interface are available in these µCs, and simpler µC versions that require
external ADCs or DACs are also useful. Often, simpler µC versions that require external ADCs or DACs are more flexible and
ultimately more useful.
The ROM and RAM requirements for charger applications are modest. In general, you can implement a single-chemistry charger in
less than 0.5kbytes of code and 32 bytes of RAM (simple requirements for even a low-end PIC). With some ingenuity, you can
implement a multi-chemistry charger with about 50% more code.
The simplest way to develop µC code is to start with a skeleton or a piece of similar code, and modify it to suit your needs. This
approach gets a prototype working quickly by overcoming a lot of the blank-page, compiler/assembler- syntax problems.
Unfortunately, only a limited amount of battery-charger firmware exists on the Web and in standard application notes. However, two
design examples in the Hardware and Software Examples section provide a starting point. See the Resources and references
section for more information on some of the more difficult toolbox routines, such as SMBus communications and math routines, and
for examples of program designs that illustrate approaches to these designs.
Tips for Charger-Program Structure
Writing battery-charger software is straightforward and best implemented with a state machine. Define a state variable or series of
flags that represents the current state. The code then tends to be a large case statement that acts according to this state variable.
The code modules modify the state variable according to the current conditions. Disallowed and undecodable states pose the only
potential problems. All case statements must have a default case that picks up these disallowed or "impossible" states and corrects
them. Always include a mechanism that detects these conditions and then takes intelligent action, such as stopping the charger.
Keep the code simple: avoid multiple interrupts and complex multitasking or queuing structures where possible. Using a single timertick interrupt is a very effective way to keep time. If the CPU has a timer with an interrupt, use it to maintain system-timer flags. This
powerful technique is an exception to the no-interrupts rule. If no timer interrupt is available (as in the PIC16C5x), use the system
timer (RTC) and poll it. Design the code so the timer cannot overflow between polls.
Avoid hardware interrupts. Instead, poll the hardware inputs at regular intervals set by the timer tick. Code execution takes place in
real time, but it doesn't have to react immediately to stimuli. The 100ms required to determine whether the battery is installed is
acceptable, considering that battery charging takes an hour. Typical performance for stand-alone chargers is usually one calculation
per minute for termination.
A simple and workable structure for these programs is a paced loop. The main program is a loop that looks at timer flags set by a
timer interrupt-service routine or the loop itself, and calls subroutines that perform the multiple tasks required. Some routines run on
each pass, and others run on every "nth" loop or tick. The basic tick time might be 100ms, for example. A blinking-light subroutine
with a half-second period would be called to complement the LED every five ticks, and the temperature-limit detector would be
checked on each pass through the loop. The result is a very robust structure.
For controllers that lack a timer interrupt, the paced loop can be implemented by the routines themselves, using their own execution
times to maintain system timing. This technique is implemented in the next section by the code example for an 8-pin PIC controller.
A simple flow chart of this structure (Figure 7) is described in greater detail in Reference 7.
Page 8 of 13
Figure 7. Main paced-loop flow chart.
Hardware Fail-Safe Reminder
Before exploring some examples, one final recommendation is to consider the use of a µP supervisor with a watchdog timer and a
hardware fail-safe system. The supervisor's reset function provides a clean system reset when the power comes up, and the
watchdog timer can catch a stalled CPU or errant firmware stuck in a loop. Maxim also makes some simple temperaturemeasurement/control products. The MAX6501 temperature switches make an especially good backup system. They are SOT23
devices that change their output level when a fixed temperature threshold is crossed.
Supervisors are especially important in charger applications, because the constant application and removal of power to the charger
can confuse the CPU. If, for example, the processor stalls and fails to terminate a fast charge, the results can be catastrophic. The
system should also include a temperature sensor or other hardware override that can end the fast charge without software
intervention. Some of Maxim's SOT23-reset supervisors include a watchdog (see the MAX823).
Hardware and software examples
1. MAX846A Li+ charger with charge timer and LED-status outputs, controlled by an 8-pin PIC
In this example, a small external µP enhances the MAX846A, forming a complete desktop-charger system that includes userinterface functions such as the LEDs in Figure 8 (to indicate the charge process and status). The MAX846A is designed for
this type of operation. Its auxiliary linear regulator and µP-reset circuit (to support the external µC) reduces the cost of a
typical desktop-charger application.
Page 9 of 13
Figure 8. Li+ desk charger with LED status indicator.
2. MAX1647-based, 2A Li+ charger with 8051 µC
The full-featured MAX1647 charger and 8051 µC form a full-featured Li+ charger (Figure 9). The Atmel 80C2051 controller
shown (a nonexpandable 8051 in a small package) is typical of the controllers usually available in systems requiring a highend charger. Source code for the application includes SMBus communications, a general state-machine structure, and other
useful routines. Look for LI1647.doc and PIC846.doc under "Other Software." The charger status can be read out from the
UART or by additional software residing in the µP.
Page 10 of 13
Figure 9. Full-featured Li+ charger.
3. Software examples for the MAX1647 and MAX846A chargers
Software for the MAX1647 and MAX846A examples (Figure 9) is available at Maxim's web site. MAX846A software for the 8pin PIC12C508 controller is written in Microchip PIC assembly language. It implements an LED user interface and a timer that
terminates the fast charge five minutes after reaching the Li+ voltage limit. This simple example does not include the state
machine or the complexities of a full charger, because much of that capability is available in the nearly stand-alone MAX846A.
The example does rely on the paced-loop structure without interrupts, as described earlier.
The MAX1647 example is written in 8051 assembly code for Atmel's ATM80C2051, a 20-pin version of the 8051. This code includes
a general state-machine structure and SMBus-driver routines for communicating with the MAX1647 internal registers. It also
incorporates a paced-loop structure, but employs the 80C2051's timer interrupt to create a timer-tick basis for all timing. For further
details, see the source-code documents at Maxim's web site.
Resources and References
The following is a brief sampling of application notes and other resources available on the World Wide Web and from vendors. Most
vendors publish their application notes on the web for easy access. Simply accessing the web and entering a µC part number into
the AltaVista search engine usually yields more than 50 documents.
Page 11 of 13
8051-Derivative Application Notes
Philips Semiconductors: Web site and CD-ROM
AN422: Using the 8XC751 Microcontroller as an I²C Bus Master
AN428: Using the ADC and PWM of the 83C752/87C752
AN439: 87C751 Fast NiCd Charger
EIE/AN92001: Low RF-Emission Applications with a P83CE654 Microcontroller
Intel Corp.: Web site and CD-ROM
Atmel Corp.: Web site and CD-ROM
A Digital Thermometer Using the AT89C2051 Microcontroller
Interfacing 24CXXX Serial EEPROMs with AT89CX051 MCU
68HC05 Application Notes
AN1263: Designing for Electromagnetic Compatibility with Single-Chip Microcontrollers
AN1262: Simple Real-Time Kernels for HC05 MCUs
AN1256: Interfacing the HC05 MCU to a Multichannel D/A Converter
AN1241: Interfacing the HC05 MCU to Serial EEPROMs
AN1227: Using Serial EEPROMs with HC05 MCUs
AN477: Simple A/D Conversion for MCUs Without Built-In ADCs
PIC Application Notes
Microchip: Web site and CD-ROM
AN541:
AN546:
AN554:
AN577:
AN552:
AN585:
AN606:
AN520:
Using a PIC16C5X as a Smart I2C Peripheral
Using the A/D Converter in the PIC 16C73
Software Implementation of I2C Bus Master
PIC16C54A EMI Results
Implementing Wake-Up on Keystroke for the 16C54
A Real-Time Operating System for PIC16/17
Low-Power Design Using PIC16/17
A Comparison of Low-End 8-bit Microcontrollers
Parallax: Third-party web site and tools References
1.
2.
3.
4.
5.
6.
7.
How to Implement an SMBus controller using the 80C51SL KBC, Intel Corp. application note, November 1994.
Handbook of Batteries, by David Linden (Editor), 2nd Edition, McGraw Hill text, January 1995, ISBN: 0070379211
The System Management Bus specification, Versions 0.95a and 1.0, Intel Corp., February 1995.
The Smart-Battery Data specification, Version 1.0, Duracell Inc. and Intel Corp., February 1995.
The SMBus BIOS specification, Version 1.0, Intel Corp., February 1995.
Smart-Battery Selector specification, Version 0.9, Intel Corp., April 1995.
Understanding Small Microcontrollers, by James Sibigtroth. Published by Motorola Inc., CSIC Division, circa 1990.
Related Parts
MAX1640
Adjustable-Output, Switch-Mode Current Sources with
Synchronous Rectifier
MAX1926
Switch-Mode 1-Cell Li+ Chargers
MAX6501
Low-Cost, +2.7V to +5.5V, Micropower Temperature Switches
in SOT23
MAX712
NiCd/NiMH Battery Fast-Charge Controllers
MAX713
NiCd/NiMH Battery Fast-Charge Controllers
MAX745
Switch-Mode Lithium-Ion Battery-Charger
MAX846A
Cost-Saving, Multichemistry, Battery Charger System
-- Free samples
-- Free samples
-- Free samples
-- Free samples
-- Free samples
Page 12 of 13
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Application note 680: http://www.maxim-ic.com/an680
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Page 13 of 13
Nicd 电池充电器
Nicd 电池充电器
镍镉 Nicd 电池是最早应用的可充电电池 其能量密度和重量密度相对较低 但是 由于成本
较低 目前仍在许多产品中被选用 如无绳电话 便携式仪表等 Nicd 电池充电终止检测方式一般采
用 - V 检测 超时检测 电池温度检测和电池温度上升率检测 快充方式下 通常选用- V 检测
与超时 温度检测相配合的方式
图一
Nicd 电池充电器
图一为利用 MAX713 构成的 Nicd 电池单机充电器 可充 1 至 16 节电池 图中 MAX713 内置充电
终止检测算法 - V 检测 超时检测 电池温度检测 快速充电结束后自动切换到涓流充电 以补
充 Nicd 电池的自放电 DCIN 接墙上适配器的输出 墙上适配器的最低输出电压应高于 2V+ 1.9V x
电池节数 最高电压取决于 P 沟道 MOSFET 的击穿电压和输入旁路电容的耐压值 当 DCIN 低于 15V
时 MAX713 的 DRV 引脚直接与 Q1 Q2 连接 DCIN 高于 15V 时 接入 Q3 R4 为 Q1 Q2 提供适当的电
压摆幅 限流二极管 D4 扩大了输入电压范围 为 MAX713 内部并联稳压源提供固定的 8mA 电流 如果
Nicd 电池充电器
墙上适配器提供的输出电压范围较窄 可以用电阻替代 D4 根据所要求的充电速率和电池容量可算出
所要求的充电电流 IFAST 由公式 RSENSE=0.25V/IFAST 确定限流电阻 RSENSE 的大小 改变 PGM0--PGM4 的接
法可设置电池节数和充电限制时间 参考表一 表二 图一中 L1 的电感量为 220 H 饱和电流为
1.5A 对电感值的要求并不严格 电感值越大 电流纹波越小
为 Nicd 电池充电时 不完全放电会使隔阳极变为镉氢氧化物 造成电池端电压下降 为消除电
池的记忆效应 图一种虚线框内的预处理电路能够使电池充电前完全放电 用 MAX712 替代 MAX713
去掉虚线框内电路 图一可用于 NiMH 电池的充电