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| 型号： | MIC2202YMM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 8/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.6A 10MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 0.5V |
| 输入电压： | 2.3 V ~ 5.5 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 2MHz |
| 电流 - 输出： | 600mA |
| 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-MSOP |
| 其它名称： | MIC2202YMMTR MIC2202YMMTR-ND |
V OUT × I OUT
Efficiency Loss = ? 1 ? ? ? ? × 100
V OUT × I OUT + L PD
? ?
? ? ?
?
R2 =
? ?
? 1 ? ?
Micrel, Inc.
The shaded region, 200mA to 500mA, efficiency loss is
dominated by MOSFET RDS (ON) and inductor DC losses.
Higher input supply voltages will increase the Gate-to-
Source threshold on the internal MOSFETs, reducing the
internal RDS (ON) . 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;
LPD = IOUT2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows:
? ? ? ?
?
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.
Alternatively, under lighter loads, the ripple current due
to the inductance becomes a significant factor. When
light load efficiencies become more critical, a larger
inductor value maybe desired. Larger inductances
reduce the peak-to-peak ripple current which minimize
losses. The following graph illustrates the effects of
inductance value at light load.
MIC2202
These values can be interchanged (i.e. 1μH inductor and
a 2.2μF capacitor). The trade off between changing
these values is that with a larger inductor, there is a
reduced peak-to-peak current which yields a greater
efficiency at lighter loads. A larger output capacitor will
improve transient response by providing a larger hold up
reservoir of energy to the output.
Feedback
The MIC2202 provides a feedback pin to adjust the
output voltage to the desired level. This pin connects
internally to an error amplifier. The error amplifier then
compares the voltage at the feedback to the internal
0.5V reference voltage and adjusts the output voltage to
maintain regulation. To calculate the resistor divider
network for the desired output is as follows:
R1
? V OUT ?
? V REF ?
Where V REF is 0.5V and V OUT is the desired output
voltage. A 10k ? or lower resistor value from the output
to the feedback is recommended. Larger resistor values
require an additional capacitor (feed-forward) from the
output to the feedback. The large high side resistor value
and the parasitic capacitance on the feedback pin
(~10pF) can cause an additional pole in the loop. The
additional pole can create a phase loss at high
frequency. This phase loss degrades transient response
100
80
Efficiency
vs. Inductance
4.7μH
by reducing phase margin. Adding feed-forward
capacitance negates the parasitic capacitive effects of
the feedback pin. A minimum 1000pF capacitor is
recommended for feed-forward capacitance.
Also, large feedback resistor values increase the
60
40
2.2μH
1μH
impedance, making the feedback node more susceptible
to noise pick-up. A feed-forward capacitor would also
reduce noise pick-up by providing a low impedance path
to the output.
20
0
0
1.8V OUT
25 50 75 100
OUTPUT CURRENT (mA)
PWM Operation
The MIC2202 is a pulse width modulation (PWM)
controller. By controlling the ratio of on-to-off time, or
duty cycle, a regulated DC output voltage is achieved.
Figure 3. Efficiency vs. Inductance
Compensation
The MIC2202 is an internally compensated, voltage
mode buck regulator. Voltage mode is achieved by
creating an internal 2MHz ramp signal and using the
output of the error amplifier to pulse width modulate the
switch node, maintaining output voltage regulation. With
a typical gain bandwidth of 200kHz, the MIC2202 is
capable of extremely fast transient responses.
The MIC2202 is designed to be stable with a 2.2μH
inductor and a 1μF ceramic (X5R) output capacitor.
As load or supply voltage changes, so does the duty
cycle to maintain a constant output voltage. In cases
where the input supply runs into a dropout condition, the
MIC2202 will run at 100% duty cycle.
The MIC2202 provides constant switching at 2MHz with
synchronous internal MOSFETs. The internal MOSFETs
include a high-side P-Channel MOSFET from the input
supply to the switch pin and an N-Channel MOSFET
from the switch pin to ground. Since the low-side N-
Channel MOSFET provides the current during the off
cycle, a free wheeling Schottky diode from the switch
node to ground is not required.
March 2007
8
M9999-031907
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相关代理商/技术参数 |
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| MIC2203 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:High Efficiency 1MHz Synchronous Buck Regulator |
| MIC2203BML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:High Efficiency 1MHz Synchronous Buck Regulator |
| MIC2203BML TR | 功能描述:IC REG BUCK ADJ 0.3A 10MLF RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 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 |
| MIC2203BMM | 功能描述:IC REG BUCK ADJ 0.3A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 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 |
| MIC2203BMM TR | 功能描述:IC REG BUCK ADJ 0.3A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 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 |
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