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| 型号： | MIC4685BR |
| 厂商： | Micrel Inc |
| 文件页数： | 10/17页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 3A SPAK-7 |
| 标准包装： | 48 |
| 系列： | SuperSwitcher™ |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 1.235V |
| 输入电压： | 4 V ~ 30 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 3A |
| 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： | SPak（7 引线 + 接片） |
| 包装： | 散装 |
| 供应商设备封装： | S-PAK-7 |
Micrel, Inc.
Functional Diagram
Bootstrap
Charger
V IN
IN
MIC4685
V OUT = V REF ?
+ 1 ?
Enable
Internal
Regulator
? R1
? R2
?
?
R1 = R2 ? OUT –1 ?
200kHz
Oscillator
Thermal
Shutdown
Current
Limit
? V ?
? V REF ?
V REF = 1.235V
Com-
parator
Reset
Driver
SW
V OUT
C OUT
R1
FB
Error
Amp
1.235V
Bandgap
Reference
R2
MIC4685
Figure 1. Adjustable Regulator
Functional Description
The MIC4685 is a variable duty cycle switch-mode
regulator with an internal power switch. Refer to the
above block diagram.
Supply Voltage
The MIC4685 operates from a +4V to +30V (34V
transient) unregulated input. Highest ef ? ciency operation
is from a supply voltage around +12V. See the ef ? ciency
curves in the “ Typical Characteristics ” section on page 5.
Enable/Shutdown
The enable (EN) input is TTL compatible. Tie the input
high if unused. A logic-high enables the regulator. A
logic-low shuts down the internal regulator which
reduces the current to typically 150μA when V EN = 0V.
Feedback
In the adjustable version, an external resistive voltage
divider is required from the output voltage to ground,
center tapped to the FB pin. See Table 1 and Table 2 for
recommended resistor values.
Duty Cycle Control
A ? xed-gain error ampli ? er compares the feedback
signal with a 1.235V bandgap voltage reference. The
resulting error ampli ? er 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 ampli ? er
output voltage. A higher error ampli ? er voltage
(comparator inverting input) causes the comparator to
detect only the peaks of the sawtooth, reducing the duty
cycle of the comparator output. A lower feedback voltage
increases the duty cycle. The MIC4685 uses a voltage-
mode control architecture.
Output Switching
When the internal switch is ON, an increasing current
? ows 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 ? eld in L1 forces current to ? ow through
fast recovery diode D1, charging C OUT .
Output Capacitor
External output capacitor C OUT provides stabilization and
reduces ripple.
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.
January 2010
10
M9999-012610
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| MIC4685BR TR | 功能描述:IC REG BUCK ADJ 3A SPAK-7 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 |
| MIC4685BRTR | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| MIC4685WR | 功能描述:直流/直流开关调节器 3A Buck Regulator in SPAK-7 (ROHS Compliant) 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 |
| MIC4685WR TR | 功能描述:直流/直流开关调节器 3A Buck Regulator in SPAK-7 (ROHS Compliant) 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 |
| MIC4685WREV | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:3A SPAK SuperSwitcher Buck Regulator |
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