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| 型号： | LTC4011CFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/26页 |
| 文件大小： | 0K |
| 描述： | IC BATT CHARGER HIEFF 20TSSOP |
| 标准包装： | 74 |
| 功能： | 充电管理 |
| 电池化学： | 镍镉（NiCd）、镍金属氢化物（NiMH） |
| 电源电压： | 4.5 V ~ 34 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 供应商设备封装： | 20-TSSOP-EP |
| 包装： | 管件 |
| 产品目录页面： | 1341 (CN2011-ZH PDF) |
LTC4011
APPLICATIONS INFORMATION
operations. However, this practice is not recommended
for NiMH cells charged well above or below their 1C rate,
because fast charge termination based solely on voltage
inflection may not be adequate to protect the battery from
a severe overcharge. A resistor between 10k and 20k may
be used to connect V TEMP to V RT if the pause function is
still desired.
INTV DD Regulator Output
If BGATE is left open, the INTV DD pin of the LTC4011 can
be used as an additional source of regulated voltage in the
host system any time READY is active. Switching loads
on INTV DD may reduce the accuracy of internal analog
circuits used to monitor and terminate fast charging.
In addition, DC current drawn from the INTV DD pin can
greatly increase internal power dissipation at elevated V CC
voltages. A minimum ceramic bypass capacitor of 0.1μF
is recommended.
Calculating Average Power Dissipation
The user should ensure that the maximum rated IC junction
temperature is not exceeded under all operating conditions.
The thermal resistance of the LTC4011 package ( θ JA )
is 38°C/W, provided the exposed metal pad is properly
soldered to the PCB. The actual thermal resistance in the
application will depend on the amount of PCB copper to
which the package is soldered. Feedthrough vias directly
below the package that connect to inner copper layers
are helpful in lowering thermal resistance. The following
formula may be used to estimate the maximum average
power dissipation P D (in watts) of the LTC4011 under
normal operating conditions.
where:
I DD = Average external INTV DD load current, if any
I VRT = Load current drawn by the external thermistor
network from V RT , if any
Q TGATE = Gate charge of external P-channel MOSFET
in coulombs
Q BGATE = Gate charge of external N-channel MOSFET
(if used) in coulombs
V LED = Maximum external LED forward voltage
R LED = External LED current-limiting resistor used in
the application
n = Number of LEDs driven by the LTC4011
Sample Applications
Figures 6 through 9 detail sample charger applications
of various complexities. Combined with the Typical Ap-
plication on the first page of this data sheet, these Figures
demonstrate some of the proper configurations of the
LTC4011. MOSFET body diodes are shown in these figures
strictly for reference only.
Figure 6 shows a minimum application, which might be
encountered in low cost NiCd fast charge applications.
FET-based PowerPath control allows for maximum input
voltage range from the DC adapter. The LTC4011 uses
– ?V to terminate the fast charge state, as no external
temperature information is available. Nonsynchronous
PWM switching is employed to reduce external component
cost. A single LED indicates charging status.
A 3A NiMH application of medium complexity is shown in
Figure 7. PowerPath control that is completely FET-based
allows for both minimum input voltage overhead and mini-
mum switchover loss when operating from the battery.
P-channel MOSFET Q4 functions as a switch to connect the
battery to the system load whenever the DC input adapter
is removed. If the maximum battery voltage is less than
the maximum rated V GS of Q4, diode D1 and resistor R5
are not required. Otherwise choose the Zener voltage
of D1 to be less than the maximum rated V GS of Q4. R5
provides a bias current of (V BAT – V ZENER )/(R5 + 20k) for
D1 when the input adapter is removed. Choose R5 to make
this current, which is drawn from the battery, just large
enough to develop the desired V GS across D1.
Precharge, fast charge and top-off states are indicated by
external LEDs. The V TEMP thermistor network allows the
LTC4011 to accurately terminate fast charge under a variety
of applied charge rates. Use of a synchronous PWM topol-
ogy improves efficiency and lowers power dissipation.
4011fb
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相关代理商/技术参数 |
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| LTC4011CFETR | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency Standalone Nickel Battery Charger |
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