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| 型号： | LT1107CN8-5 |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK BST INV 5V 0.4A 8DIP |
| 标准包装： | 50 |
| 类型： | 降压（降压），升压（升压），反相 |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 2 V ~ 30 V |
| 频率 - 开关： | 63kHz |
| 电流 - 输出： | 400mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
| 供应商设备封装： | 8-PDIP |
LT1107
A PPLICATI
S I FOR ATIO
()
? ? R ′ t ?
? 1 ? e
?
t =
I L ( 15 )
R ′ ? ?
where DC = duty cycle (0.50 in step-down mode)
V SW = switch drop in step-down mode
V D = diode drop (0.5V for a 1N5818)
I OUT = output current
V OUT = output voltage
V IN = minimum input voltage
V SW is actually a function of switch current which is in turn
a function of V IN , L, time, and V OUT . To simplify, 1.5V can
be used for V SW as a very conservative value.
Once I PEAK is known, inductor value can be derived from:
In this mode the switch is arranged in common collector
or step-down mode. The switch drop can be modeled as
a 0.75V source in series with a 0.65 ? resistor. When the
switch closes, current in the inductor builds according to:
V L
L
? ?
where R ′ = 0.65 ? + DCR L
V L = V IN – 0.75V
As an example, suppose –5V at 50mA is to be generated
V IN ( MIN ) ? V SW OUT
L =
I PEAK
? V
× t ON
( 11 )
from a 4.5V to 5.5V input. Recalling Equation (14),
P L = ( ? 5 V + 0 . 5 V ) ( 50 mA ) = 275mW
(16 )
where t ON = switch ON time (7 μ s).
Energy required from the inductor is:
= = 4 . 4 μ J
Next, the current limit resistor R LIM is selected to give
I PEAK from the Maximum Switch Current vs R LIM curve.
The addition of this resistor keeps maximum switch cur-
P L
f OSC
275 mW
63 kHz
( 17 )
rent constant as the input voltage is increased.
Picking an inductor value of 100 μ H with 0.2 ? DCR results
2 ( 300 mA ) ? 5 + 0 . 5 ?
? ? 12 ? 1 . 5 + 0 . 5 ? ?
( 4 . 5 V ? 0 . 75 V )
(
)
? 1 ? e
As an example, suppose 5V at 300mA is to be generated
from a 12V to 24V input. Recalling Equation (10):
I PEAK = ? ? = 600 mA ( 12 )
0 . 50
in a peak switch current of:
I PEAK =
0 . 65 ? + 0 . 2 ?
= 325 mA
?
?
?
? 0.85 ? ? 9 μ s ?
100 μ H ?
?
?
( 18 )
Next, inductor value is calculated using Equation (11):
Substituting I PEAK into Equation (04) results in:
L =
12 ? 1.5 ? 5
600 mA
7 μ s = 64 μ H
( 13 )
E L =
1
2
( 100 μ H )( 0 . 325 A
) 2 = 5 . 28 μ J
( 19 )
Use the next lowest standard value (56 μ H).
Then pick R LIM from the curve. For I PEAK = 600mA, R LIM
= 56 ? .
Inductor Selection –– Positive-to-Negative Converter
Figure 4 shows hookup for positive-to-negative conver-
sion. All of the output power must come from the inductor.
In this case,
Since 5.28 μ J > 3.82 μ J, the 100 μ H inductor will work.
With this relatively small input range, R LIM is not usually
necessary and the I LIM pin can be tied directly to V IN . As in
the step-down case, peak switch current should be limited
to ~650mA.
Step-Up (Boost Mode) Operation
A step-up DC/DC converter delivers an output voltage
P L = ( V OUT D ) ( OUT )
+ V I
(14)
higher than the input voltage. Step-up converters are not
short-circuit protected since there is a DC path from input
to output.
1107fa
8
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相关代理商/技术参数 |
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| LT1107CN8-5#PBF | 功能描述:IC REG BUCK BST INV 5V 0.4A 8DIP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT1107CS8 | 制造商:Linear Technology 功能描述:Conv DC-DC Single Non-Inv/Inv/Step Up/Step Down 2V to 30V 8-Pin SOIC N |
| LT1107CS8#PBF | 功能描述:IC REG BUCK BOOST INV ADJ 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1107CS8#TR | 功能描述:IC REG BUCK BOOST INV ADJ 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT1107CS8#TRPBF | 功能描述:IC REG BUCK BOOST INV ADJ 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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