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参数资料
| 型号： | MIC2238-GFHYML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 0.8A DL 12MLF |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 2 |
| 输出电压： | 1.58V，1.8V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 2.5MHz |
| 电流 - 输出： | 800mA |
| 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： | 12-VFDFN 裸露焊盘，12-MLF? |
| 包装： | 标准包装 |
| 供应商设备封装： | 12-MLF?（4x4） |
| 产品目录页面： | 1095 (CN2011-ZH PDF) |
| 其它名称： | 576-2122-6 576-2122-6-ND 576-2972-6 |
Efficiency _Loss = ? 1 ? ? ?
? ? × 100
? V OUT × I OUT + L_Pd ? ? ?
? ?
Micrel, Inc.
battery powered applications. Reduced current draw
from a battery increases the devices operating time and
is critical in hand held devices.
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I 2 R. Power is dissipated in the
high side switch during the on cycle. Power loss is equal
to the high side MOSFET R DSON multiplied by the Switch
Current 2 . During the off cycle, the low side N-channel
MOSFET conducts, also dissipating power. Device
operating current also reduces efficiency. The product of
the quiescent (operating) current and the supply voltage
is another DC loss. The current required driving the
gates on and off at a constant 2.5MHz frequency and the
switching transitions make up the switching losses.
The Figure above shows an efficiency curve. From no
load to 100mA, efficiency losses are dominated by
quiescent current losses, gate drive and transition
losses. By Forcing the MIC2238 into Trickle Mode
(/FPWM=High), the buck regulator significantly reduces
the required switching current by entering into a PFM
(Pulse Frequency Modulation) mode. This significantly
increases efficiency at low output currents.
Over 100mA, efficiency loss is dominated by MOSFET
RDSON and inductor losses. Higher input supply
voltages will increase the Gate to Source threshold on
the internal MOSFETs, reducing the internal RDSON.
MIC2238
This improves efficiency by reducing DC losses in the
device. All but the inductor losses are inherent to the
device. In which case, inductor selection becomes
increasingly critical in efficiency calculations. As the
inductors are reduced in size, the DC resistance (DCR)
can become quite significant. The DCR losses can be
calculated as follows;
L_Pd = Iout 2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows;
? ? V OUT × I OUT ? ?
?
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
Trickle Mode Operation
Trickle Mode operation is achieved by clamping the
minimum peak current to approximately 150mA. This
forces a PFM mode by comparing the output voltage to
the internal reference. If the voltage is less than 0.8V,
the MIC2238 turns on the high side until the peak
inductor current reaches approximately 150mA. A
separate comparator then monitors the output voltage. If
the feedback voltage is greater than 0.8V, the high side
switch is used as a 10μA current source, never turning
completely off. This creates a highly efficient light load
mode by increasing the time it takes for the output
capacitor to discharge, delaying the amount of switching
required and increasing light load efficiency. When the
load current is greater than approximately 100mA, the
MIC2238 automatically switches to PWM mode.
FPWM Operation
In Forced PWM Mode (/FPWM=LOW) the MIC2238 is
forced to provides constant switching at 2.5MHz with
synchronous internal MOSFETs throughout the load
current.
April 2010
12
M9999-040810-A
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2238-GSYML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2.5MHz Dual Phase PWM Buck Regulator |
| MIC2238-GSYML TR | 功能描述:直流/直流开关调节器 High Efficiency Dual 800/800mA Buck 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 |
| MIC2238-GSYML-TR | 功能描述:Buck Switching Regulator IC Positive Fixed 1.8V, 3.3V 2 Output 800mA 12-VFDFN Exposed Pad, 12-MLF? 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:固定 输出数:2 电压 - 输入（最小值）:2.5V 电压 - 输入（最大值）:5.5V 电压 - 输出（最小值/固定）:1.8V，3.3V 电压 - 输出（最大值）:- 电流 - 输出:800mA 频率 - 开关:2.5MHz 同步整流器:是 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:12-VFDFN 裸焊盘，12-MLF? 供应商器件封装:12-MLF?（4x4） 标准包装:1 |
| MIC2238-GWYML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2.5MHz Dual Phase PWM Buck Regulator |
| MIC2238-J4YML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2.5MHz Dual Phase PWM Buck Regulator |
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