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| 型号： | MIC2179BSM |
| 厂商： | Micrel Inc |
| 文件页数： | 7/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1.5A 20SSOP |
| 标准包装： | 67 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.25 V ~ 16.5 V |
| 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： | 1.5A |
| 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-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 20-SSOP |
Micrel, Inc.
Functional Description
Micrel’s MIC2179 is a synchronous buck regulator that oper-
ates from an input voltage of 4.5V to 16.5V and provides a
regulated output voltage of 1.25V to 16.5V. Its has internal
power MOSFETs that supply up to 1.5A load current and
operates with up to 100% duty cycle to allow low-dropout
operation. To optimize efficiency, the MIC2179 operates in
PWM and skip mode. Skip mode provides the best efficiency
when load current is less than 150mA, while PWM mode is
more efficient at higher current. PWM or skip-mode opera -
tion is selected externally, allowing an intelligent system (i.e.
microprocessor controlled) to select the correct operating
mode for efficiency and noise requirements.
During PWM operation, the MIC2179 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, under-
voltage lockout, and thermal shutdown. See the following
sections for more detail.
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 150mΩ when
the MIC2179 operates from a 12V supply. Antishoot-through
circuitry prevents the P-channel and N-channel from turning
on at the same time.
Current Limit
The MIC2179 uses pulse-by-pulse current limiting to protect
the output. During each switching period, a current limit com-
parator detects if the P-Channel current exceeds 4.3A. 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 to 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 MIC2179
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.
Shutdown Mode
The MIC2179 has a low-current shutdown mode that is con-
trolled by the enable input (EN). When a logic 0 is applied
to EN, the MIC2179 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 MIC2179
control circuits. This internal supply is brought out to the BIAS
pin for bypassing by an external 0.01μF capacitor. Do not
MIC2179
connect an external load to the BIAS pin. It is not designed
to provide an external supply voltage.
Frequency Synchronization
The MIC2179 operates at a preset switching frequency of
200kHz. It can be synchronized to a higher frequency by con-
necting 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 to 300kHz, and can operate with a minimum pulse
width of 500ns. If synchronization is not required, connect
SYNC to ground.
Power Good Flag
The power good flag (PWRGD) is an error flag that alerts a
system when the output is not in regulation. When the output
voltage is 10% below its nominal value, PWRGD is logic low,
signaling that V OUT is to low. PWRGD is an open-drain output
that can sink 1mA from a pull-up resistor connected to V IN .
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 simpli-
fied block diagram of the MIC2179 operating in PWM mode
and 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 ampli-
fier (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 sawtooth waveform (corrective
ramp) generated by the oscillator, creating a composite wave-
form 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 discharged from the induc-
tor and I L1 decreases until the next switching cycle begins.
By varying the P-channel on-time (duty cycle), the average
inductor current is adjusted to whatever value is required to
regulate the output voltage.
The MIC2179 uses current-mode control to adjust the duty
cycle and regulate the output voltage. Current-mode control
has two signal loops that determine the duty cycle. One is an
outer loop that senses the output voltage, and the other is
a faster inner loop that senses the inductor current. Signals
from these two loops control the duty cycle in the following
way: V OUT is fed back to the error amplifier which compares
the feedback voltage (V FB ) to an internal reference voltage
June 2009
7
M9999-063009
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2179BSM TR | 功能描述:直流/直流开关调节器 1.5A 200kHz Synchronous Switcher in SSOP Pkg 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 |
| MIC2179SYM | 制造商:RF Micro Devices Inc 功能描述: |
| MIC2179YSM | 功能描述:直流/直流开关调节器 1.5A 200kHz Synchronous Switcher in SSOP Pkg (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 |
| MIC2179YSM TR | 功能描述:直流/直流开关调节器 1.5A 200kHz Synchronous Switcher in SSOP Pkg (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 |
| MIC2179YSM-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 1.245V 1 Output 1.5A 20-SSOP (0.209", 5.30mm Width) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 功能:降压 输出配置:正 拓扑:降压 输出类型:可调式 输出数:1 电压 - 输入（最小值）:4.5V 电压 - 输入（最大值）:16.5V 电压 - 输出（最小值/固定）:1.245V 电压 - 输出（最大值）:16.5V 电流 - 输出:1.5A 频率 - 开关:200kHz 同步整流器:无 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:20-SSOP（0.209"，5.30mm 宽） 供应商器件封装:20-SSOP 标准包装:1 |
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