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参数资料
| 型号： | LTC3550EDHC-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/24页 |
| 文件大小： | 0K |
| 描述： | IC CHARGER BATT DUAL 16-DFN |
| 标准包装： | 2,500 |
| 功能： | 充电管理 |
| 电池化学： | 锂离子（Li-Ion） |
| 电源电压： | 4.3 V ~ 8 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WFDFN 裸露焊盘 |
| 供应商设备封装： | 16-DFN（5x3） |
| 包装： | 带卷 (TR) |
LTC3550-1
APPLICATIO S I FOR ATIO
Thermal Considerations
The battery charger’s thermal regulation feature and the
buck regulator’s high ef?ciency make it unlikely that enough
Most of the charger’s power dissipation is generated from
the internal charger MOSFET. Thus, the power dissipation
is calculated to be:
power is dissipated to exceed the LTC3550-1 maximum
P D(CHARGER) = (V IN – V BAT ) ? I BAT
(5)
junction temperature. Nevertheless, it is a good idea to
do some thermal analysis for worst-case conditions.
The junction temperature, T J , is given by: T J = T A + T RISE
where T A is the ambient temperature. The temperature
rise is given by:
T RISE = P D ? θ JA
where P D is the power dissipated and θ JA is the thermal
resistance from the junction of the die to the ambient
temperature.
In most applications the buck regulator does not dissipate
much heat due to its high ef?ciency. The majority of the
LTC3550-1 power dissipation occurs when charging a
battery. Fortunately, the LTC3550-1 automatically reduces
the charge current during high power conditions using
a patented thermal regulation circuit. Thus, there is no
need to design for worst-case power dissipation scenarios
because the LTC3550-1 ensures that the battery charger
power dissipation never raises the junction temperature
above a preset value of 105°C. In the unlikely case that
the junction temperature is forced above 105°C (due to
abnormally high ambient temperatures or excessive buck
regulator power dissipation), the battery charge current will
be reduced to zero and thus dissipate no heat. As an added
measure of protection, even if the junction temperature
reaches approximately 150°C, the buck regulator’s power
V IN is the charger supply voltage (either DCIN or USBIN),
V BAT is the battery voltage and I BAT is the charge cur-
rent.
Example: An LTC3550-1 operating from a 5V wall adapter
(on the DCIN input) is programmed to supply 650mA
full-scale current to a discharged Li-Ion battery with a
voltage of 2.7V.
The charger power dissipation is calculated to be:
P D(CHARGER) = (5V – 2.7V) ? 650mA = 1.495W
For simplicity, assume the buck regulator is disabled and
dissipates no power (P D(BUCK) = 0). For a properly soldered
DHC16 package, the thermal resistance ( θ JA ) is 40°C/W.
Thus, the ambient temperature at which the LTC3550-1
charger will begin to reduce the charge current is:
T A = 105°C – 1.495W ? 40°C/W
T A = 105°C – 59.8°C
T A = 45.2°C
The LTC3550-1 can be used above 45.2°C ambient, but
the charge current will be reduced from 650mA. Assum-
ing no power dissipation from the buck converter, the
approximate current at a given ambient temperature can
be approximated by:
switches will be turned off and the SW node will become
high impedance.
I BAT =
105 ° C – T A
( V IN – V BAT ) ? θ JA
(6)
I BAT =
=
TheconditionsthatcausetheLTC3550-1toreducecharge
current through thermal feedback can be approximated by
considering the power dissipated in the IC. The approxi-
mate ambient temperature at which the thermal feedback
begins to protect the IC is:
T A = 105°C – T RISE
T A = 105°C – (P D ? θ JA )
Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to approxi-
mately:
105 ° C – 60 ° C 45 ° C
( 5 V – 2 . 7 V ) ? 40 ° C / W 92 ° C / A
I B AT = 489 mA
T A = 105°C – (P D(CHARGER) + P D(BUCK) ) ? θ JA
(4)
Because the regulator typically dissipates signi?cantly less
heat than the charger (even in worst-case situations), the
calculations here should work well as an approximation.
35501f
18
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相关代理商/技术参数 |
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| LTC3552 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Standalone Linear Li-Ion Battery Charger and Dual Synchronous Buck Converter |
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| LTC3552EDHC | 制造商:LINER 制造商全称:Linear Technology 功能描述:Standalone Linear Li-Ion Battery Charger and Dual Synchronous Buck Converter |
| LTC3552EDHC#PBF | 功能描述:IC CHARGER BATT LI-ION 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC3552EDHC#TRPBF | 功能描述:IC CHARGER BATT LI-ION 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
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