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| 型号： | MIC4681-5.0BM |
| 厂商： | Micrel Inc |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 1A 8SOIC |
| 标准包装： | 380 |
| 系列： | SuperSwitcher™ |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 4 V ~ 30 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 1A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°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 |
MIC4681
Functional Description
The MIC4681 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
Supply Voltage
The MIC4681 operates from a +4V to +30V unregulated
input. Highest efficiency operation is from a supply voltage
around +12V. See the efficiency curves on page 6.
Enable/Shutdown
The shutdown ( SHDN ) input is TTL compatible. Ground the
input if unused. A logic-low enables the regulator. A logic-
high shuts down the internal regulator which reduces the
current to typically 35 μ A when V SHDN = V IN = 12V and 6 μ A
when V SHDN = 5V. See “ Shutdown Input Behavior: Shutdown
Hysteresis. ”
Feedback
Require an external resistive voltage divider from the output
voltage to ground, center tapped to the FB pin. See Figure 1b
for recommended resistor values.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 200kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.
A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.23V feedback signal. Rec-
ommended voltage-divider resistor values for common out-
Micrel
inverting input) causes the comparator to detect only the
peaks of the sawtooth, reducing the duty cycle of the com-
parator output. A lower feedback voltage increases the duty
cycle. The MIC4681 uses a voltage-mode control architec-
ture.
Output Switching
When the internal switch is ON, an increasing current flows
from the supply V IN, through external storage inductor L1, to
output capacitor C OUT and the load. Energy is stored in the
inductor as the current increases with time.
When the internal switch is turned OFF, the collapse of the
magnetic field in L1 forces current to flow through fast
recovery diode D1, charging C OUT .
Output Capacitor
External output capacitor C OUT provides stabilization and
reduces ripple. See “ Bode Plots ” for additional information.
Return Paths
During the ON portion of the cycle, the output capacitor and
load currents return to the supply ground. During the OFF
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.
put voltages are included in Figure 1b.
For other voltages, the resistor values can be determined
using the following formulas:
SHUTDOWN
ENABLE
V IN
C IN
2
1
MIC4681BM
IN SW
SHDN FB
3
4
L1
R1
V OUT
C OUT
V OUT = V REF ?
+ 1 ?
? R1
? R2
?
?
GND
5 – 8
D1
R2
R1 = R2 ? OUT ? 1 ?
? V ?
? V REF ?
V REF = 1.23V
Figure 1a. Adjustable Regulator Circuit
V O U T
R 1 *
R 2 *
C I N
D 1
L 1
C O U T
1 . 8 V 3 . 0 1 k 6 . 4 9 k
2 . 5 V 3 . 0 1 k 2 . 9 4 k
3 . 3 V 3 . 0 1 k 1 . 7 8 k
2 2 μ F 3 5 V
V i s h a y D a l e
3 A 4 0 V S c h o t t k y
B 3 4 0 A V i s h a y - D i o d e , I n c . * * *
6 8 μ H 2 . 0 A
C o i l t r o n i c s U P 3 B - 6 8 0
2 2 0 μ F 1 0 V
V i s h a y D a l e
5 . 0 V 3 . 0 1 k 9 7 6 ?
6 . 0 V 3 . 0 1 k 7 8 7 ?
5 9 3 D 2 2 6 X 0 3 5 E 2 T
o r o r
S S 3 6 G e n e r a l S e m i c o n d u c t o r S u m i d a C D R H 1 2 7 - 6 8 0 M C * *
5 9 4 D 2 2 7 X 0 0 1 0 D 2
* A l l r e s i s t o r s 1 %
* * s h i e l d e d m a g n e t i c s f o r l o w R F I a p p l i c a t i o n s
* * * V i s h a y - D i o d e , I n c . ( 8 0 5 ) 4 4 6 - 4 8 0 0
Figure 1b. Recommended Components for Common Ouput Voltages
April 2005
11
MIC4681
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC4681BM | 功能描述:IC REG BUCK ADJ 1A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:SuperSwitcher™ 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
| MIC4681BM TR | 功能描述:IC REG BUCK ADJ 1A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:SuperSwitcher™ 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
| MIC4681YM | 功能描述:直流/直流开关调节器 2A Peak SuperSwitcher in SO-8 (Lead Free) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC4681YM TR | 功能描述:直流/直流开关调节器 2A Peak SuperSwitcher in SO-8 (Lead Free) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC4682 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:PRECISION CURRENT LIMIT SO-8 SUPERSWITCHER BUCK REGULATOR |
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