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LT1513CR 参数 Datasheet PDF下载

LT1513CR图片预览
型号: LT1513CR
PDF下载: 下载PDF文件 查看货源
内容描述: SEPIC Constant-或可编程电流/恒定电压电池充电器 [SEPIC Constant- or Programmable-Current/ Constant-Voltage Battery Charger]
分类和应用: 稳压器开关式稳压器或控制器电源电路电池开关式控制器
文件页数/大小: 16 页 / 303 K
品牌: Linear [ Linear ]
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LT1513/LT1513-2  
U
W U U  
APPLICATIONS INFORMATION  
vary depending on the mounting technique (copper area,  
airflow, etc.).  
current Schottky diodes have relatively high leakage cur-  
rents (5µA to 500µA) even at room temperature. The latest  
very-low-forward devices have especially high leakage cur-  
rents.Ithasbeennotedthatsurfacemountversionsofsome  
Schottky diodes have as much as ten times the leakage of  
their through-hole counterparts. This may be because a low  
forwardvoltageprocessisusedtoreducepowerdissipation  
in the surface mount package. In any case, check leakage  
specifications carefully before making a final choice for the  
switching diode. Be aware that diode manufacturers want  
to specify a maximum leakage current that is ten times  
higher than the typical leakage. It is very difficult to get them  
to specify a low leakage current in high volume production.  
This is an on going problem for all battery charger circuits  
and most customers have to settle for a diode whose typical  
leakage is adequate, but theoretically has a worst-case  
condition of higher than desired battery drain.  
Average supply current (including driver current) is:  
(V )(I  
)(0.024)  
BAT CHRG  
I = 4mA +  
IN  
V
IN  
Switch power dissipation is given by:  
2
(I  
) (R )(V  
+ V )(V  
)
CHRG  
SW BAT  
IN BAT  
P
=
SW  
2
(V )  
IN  
RSW = Output switch ON resistance  
Total power dissipation of the die is equal to supply current  
times supply voltage, plus switch power:  
PD(TOTAL) = (IIN)(VIN) + PSW  
For VIN = 10V, VBAT = 8.2V, ICHRG = 1.2A, RSW = 0.3,  
IIN = 4mA + 24mA = 28mA  
Thermal Considerations  
Care should be taken to ensure that worst-case conditions  
do not cause excessive die temperatures. Typical thermal  
resistance is 30°C/W for the R package but this number will  
PSW = 0.64W  
PD = (10)(0.028) + 0.64 = 0.92W  
GROUND PLANE  
V
BAT  
+
+
C1  
C1  
D1  
LT1513 TAB AND GROUND  
PIN SOLDERED TO  
GROUND PLANE  
C2  
C5  
2 WINDING  
INDUCTOR  
L1A  
L1B  
+
R5  
C3  
R3  
C1,C3,C5 AND R3  
TIED DIRECTLY TO  
GROUND PLANE  
LT1513 • F04  
V
IN  
Figure 4. LT1513 Suggested Partial Layout for Critical Thermal and Electrical Paths  
9