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| 型号： | MIC2177-3.3YWM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 8/15页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 3.3V 20SOIC |
| 标准包装： | 1 |
| 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： | 4.5 V ~ 16.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 2.5A |
| 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： | 20-SOIC（0.295"，7.50mm 宽） |
| 包装： | 标准包装 |
| 供应商设备封装： | 20-SOIC（宽型） |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-1542-6 |
Micrel, Inc.
Functional Description
Micrel’s MIC2177 is a synchronous buck regulator that
operates from an input voltage of 4.5V to 16.5V and
provides a regulated output voltage of 1.25V to 16.5V. It
has internal power MOSFETs that supply up to 2.5A of
load current and operates with up to 100% duty cycle to
allow low-dropout operation. To optimize efficiency, the
MIC2177 operates in PWM and skip mode. Skip mode
provides the best efficiency when load current is less
than 200mA, while PWM mode is more efficient at higher
current. A patented technique allows the MIC2177 to
automatically select the correct operating mode as the
load current changes.
During PWM operation, the MIC2177 uses current-mode
control which provides superior line regulation and
makes the control loop easier to compensate. The PWM
switching frequency is set internally to 200kHz and can
be synchronized to an external clock frequency up to
300kHz. Other features include a low-current shutdown
mode, current limit, undervoltage lockout, and thermal
shutdown. See the following sections for details.
Switch Output
The switch output (SW) is a half H-bridge consisting of a
high-side P-channel and low-side N-channel power
MOSFET. These MOSFETs have a typical on-resistance
of 100m ? when the MIC2177 operates from a 12V
supply. Anti-shoot-through circuitry prevents the P-
channel and N-channel from turning on at the same
time.
Current Limit
The MIC2177 uses pulse-by-pulse current limiting to
protect the output. During each switching period, a
current limit comparator detects if the P-channel current
exceeds 4.7A. When it does, the P-channel is turned off
until the next switching period begins.
Undervoltage Lockout
Undervoltage lockout (UVLO) turns off the output when
the input voltage (V IN ) is too low to provide sufficient gate
drive for the output MOSFETs. It prevents the output
from turning on until V IN exceeds 4.3V. Once operating,
the output will not shut off until V IN drops below 4.2V.
Thermal Shutdown
Thermal shutdown turns off the output when the
MIC2177 junction temperature exceeds the maximum
value for safe operation. After thermal shutdown occurs,
the output will not turn on until the junction temperature
drops approximately 10°C.
MIC2177
Shutdown Mode
The MIC2177 has a low-current shutdown mode that is
controlled by the enable input (EN). When a logic 0 is
applied to EN, the MIC2177 is in shutdown mode and its
quiescent current drops to less than 5μA.
Internal Bias Regulator
An internal 3.3V regulator provides power to the
MIC2177 control circuits. This internal supply is brought
out to the BIAS pin for bypassing by an external 0.01μF
capacitor. Do not connect any external load to the BIAS
pin. It is not designed to provide an external supply
voltage.
Frequency Synchronization
The MIC2177 operates at a preset switching frequency
of 200kHz. It can be synchronized to a higher frequency
by connecting an external clock to the SYNC pin. The
SYNC pin is a logic level input that synchronizes the
oscillator to the rising edge of an external clock signal. It
has a frequency range of 220kHz–300kHz, and can
operate with a minimum pulse-width of 500ns. If
synchronization is not required, connect SYNC to
ground.
Low-Dropout Operation
Output regulation is maintained in PWM or skip mode
even when the difference between V IN and V OUT
decreases below 1V. As V IN – V OUT decreases, the duty
cycle increases until it reaches 100%. At this point, the
P-channel is kept on for several cycles at a time, and the
output stays in regulation until V IN – V OUT falls below the
dropout voltage (dropout voltage = P-channel on
resistance × load current).
PWM-Mode Operation
Refer to “PWM-Mode Functional Diagram” which is a
simplified block diagram of the MIC2177 operating in
PWM mode with its associated waveforms.
When operating in PWM mode, the output P-channel
and N-channel MOSFETs are alternately switched on at
a constant frequency and variable duty cycle. A
switching period begins when the oscillator generates a
reset pulse. This pulse resets the RS latch which turns
on the P-channel and turns off the N-channel. During
this time, inductor current (I L1 ) increases and energy is
stored in the inductor. The current sense amplifier (I SENSE
Amp) measures the P-channel drain-to-source voltage
and outputs a voltage proportional to I L1 . The output of
I SENSE Amp is added to a saw tooth waveform (corrective
ramp) generated by the oscillator, creating a composite
waveform labeled I SENSE on the timing diagram. When
I SENSE is greater than the error amplifier output, the PWM
comparator will set the RS latch which turns off the P-
channel and turns on the N-channel. Energy is then
April 2008
8
M9999-042108
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2177-5.0BWM | 功能描述:直流/直流开关调节器 2.5A 200kHz Synchronous Switcher 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 |
| MIC2177-5.0BWM TR | 功能描述:直流/直流开关调节器 2.5A 200kHz Synchronous Switcher 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 |
| MIC2177-5.0BWMTR | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| MIC2177-5.0YWM | 功能描述:直流/直流开关调节器 2.5A 200kHz Synchronous Switcher 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 |
| MIC2177-5.0YWM TR | 功能描述:直流/直流开关调节器 2.5A 200kHz Synchronous Switcher 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 |
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