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| 型号： | LT1777CS#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.7A 16SOIC |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.24 V ~ 30 V |
| 输入电压： | 12 V ~ 48 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz |
| 电流 - 输出： | 700mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 16-SOIC |
LT1777
TYPICAL APPLICATIO N S
Optional Input/Output Filtering
When minimum conducted noise is required, it is often
advantageous to add an explicit input and/or output filter
to the topology. This can be a cost-effective way to reduce
conducted noise on the input or output node by an order
of magnitude or more. The exact details involved are a bit
lengthy, so the user is referred to the thorough treatments
in Application Notes AN19 and AN44. However, an ex-
ample will be given to illustrate the principles involved.
Figure 12 shows the previous “Basic 5V Output Applica-
tion” modified with an additional input inductor and an
output L/C combination. The dramatic improvement in
noise performance is seen in the accompanying oscillo-
scope photos shown in Figures 13 and 14. Operating
conditions are V IN = 24V, I OUT = 400mA. The pair of scope
photos in Figure 13 show the response at the input node,
before and after the additional 33 μ H inductor is added. The
upper waveform shows an AC-coupled version of the
L3
33 μ H
output voltage at 50mV/DIV, and the lower waveform is a
DC-coupled representation of current into the node at
50mA/DIV. Input voltage ripple is seen to decrease from
100mV P-P to perhaps 10mV P-P . Ripple current is also seen
to decrease dramatically. (This improvement in AC ripple
current actually affects radiated magnetic noise.)
The next pair of scope photos in Figure 14 show an
AC-coupled version of the output node at 2mV/DIV.
Voltage ripple is seen to be originally about 12mV P-P , with
most of the energy in the lowest harmonics. After the
addition of a 4.7 μ H inductor and a second 100 μ F output
capacitor, ripple is about 200 μ V P-P .
These input and output inductor requirements are typically
not very difficult to achieve, and inexpensive open style
DO1608C types were used in this example. Once again,
more costly closed-construction style inductors may be
employed, but these are usually not necessary, as the AC
fields generated by these inductors are typically small.
V IN
+
10
3
V IN
SHDN
V CC
4
12
14
V C V D
LT1777
SYNC V SW
FB
6
5
13
D1
+
L4
4.7 μ H
+
V OUT
C8
100 μ F
10V
SGND
7
ADDITIONAL FILTER COMPONENTS
L3: COILCRAFT D01608C-333 OR SIMILAR
L4: COILCRAFT D01608C-472 OR SIMILAR
C8: AVX D CASE TPSD107M010R0080
1777 F12
Figure 12. Basic 5V Application with Optional Input/Output Filters
V IN NODE VOLTAGE
AC COUPLED
50mV/DIV
V IN NODE CURRENT
DC COUPLED
50mA/DIV
V IN NODE VOLTAGE
AC COUPLED
50mV/DIV
V IN NODE CURRENT
DC COUPLED
50mA/DIV
GND, CH2
2 μ s/DIV
1777 F13a
GND, CH2
2 μ s/DIV
1777 F13b
(a) Before Input Inductor
Figure 13. Input Node Ripple
(b) After Input Inductor
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1777I | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low Noise Step-Down Switching Regulator |
| LT1777IS | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC 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 |
| LT1777IS#PBF | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC 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 |
| LT1777IS#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LT1777IS#TR | 功能描述:IC REG BUCK ADJ 0.7A 16SOIC 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 |
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