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| 型号： | LTC1474CS8-3.3 |
| 厂商： | Linear Technology |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 3.3V 0.75A 8SOIC |
| 标准包装： | 100 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 3.3V |
| 输入电压： | 3 V ~ 18 V |
| PWM 型： | Burst Mode? |
| 电流 - 输出： | 750mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-SOIC |
LTC1474/LTC1475
APPLICATIO N S I N FOR M ATIO N
OUTPUT DIVIDER REQUIRED WITH
ADJUSTABLE VERSION ONLY
10pF
LTC1474
V OUT
R2
R1
1
2
V FB
LBO
8
RUN
V IN 7
100k
L
+
C OUT
3
4
LBI
GND
SENSE
SW
6
5
1000pF
R SENSE
1474/75 F09
0.1 μ F
D1
C IN
+
V IN
BOLD LINES INDICATE HIGH PATH CURRENTS
Figure 9. LTC1474/LTC1475 Layout Diagram (See Board Layout Checklist)
0 . 75 ( 3 . 3 + 0 . 4 )( 4 . 75 μ s ) = 264 μ H
L MIN =
R 2 = ? OUT ? 1 ? ? R 1 = 1 . 43 M
5. Are the signal and power grounds segregated? The
signal ground consists of the (–) plate of C OUT , Pin 4 of
the LTC1474/LTC1475 and the resistive divider. The
power ground consists of the Schottky diode anode,
the (–) plate of C IN and the 0.1 μ F decoupling capacitor.
6. Is a 100k resistor connected in series between RUN
(Pin 8) and the RUN control voltage? The resistor
should be as close as possible to Pin 8.
Design Example (Refer to R SENSE and Inductor
Selection)
As a design example, assume V IN = 10V, V OUT = 3V, and
a maximum average output current I MAX = 100mA. With
this information, we can easily calculate all the important
components:
From the equation (1),
R SENSE = (0.067/0.1) – 0.25 = 0.42 ?
Using the standard resistors (1 ? , 1 ? and 2 ? ) in parallel
provides 0.4 ? without having to use a more expensive
low value current shunt type resistor (see R SENSE Selec-
tion section).
With R SENSE = 0.4 ? , the peak inductor current I PEAK is
calculated from (2), neglecting the second term, to be
150mA. The minimum inductance is, therefore, from the
equation (3) and assuming V D = 0.4V,
0 . 15 ? 0 . 1
From Figure 3, an inductance of 270 μ H is chosen from the
recommended region. The CDRH73-271 or CD54-271 is a
good choice for space limited applications.
For the feedback resistors, choose R1 = 1M to minimize
supply current. R2 can then be calculated from the equa-
tion (4) to be:
? V ?
? 1 . 23 ?
For the catch diode, the MBR0530 will work well in this
application.
For the input and output capacitors, AVX 4.7 μ F and 100 μ F,
respectively, low ESR TPS series work well and meet the
RMS current requirement of 100mA/2 = 50mA. They are
available in small “C” case sizes with 0.15 ? ESR. The
0.15 ? output capacitor ESR will result in 25mV of output
voltage ripple.
Figure 10 shows the complete circuit for this example.
13
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相关代理商/技术参数 |
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| LTC1474CS8-5 | 功能描述:IC REG BUCK 5V 0.75A 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CS8-5#PBF | 功能描述:IC REG BUCK 5V 0.75A 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 |
| LTC1474CS8-5#TR | 功能描述:IC REG BUCK 5V 0.75A 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CS8-5#TRPBF | 功能描述:IC REG BUCK 5V 0.75A 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1474CS8PBF | 制造商:Linear Technology 功能描述:LTC1474CS8PBF |
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