参数资料
| 型号： | MIC2177BWM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 13/15页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 2.5A 20SOIC |
| 标准包装： | 1,000 |
| 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： | 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： | 带卷 (TR) |
| 供应商设备封装： | 20-SOIC（宽型） |
| 其它名称： | MIC2177BWMTR MIC2177BWMTR-ND |
R1 = R2 ? ? ?
? ? ? 1 ?
Micrel, Inc.
Application Information
Feedback Resistor Selection (Adjustable Version)
The output voltage is configured by connecting an
external resistive divider to the FB pin as shown in
“MIC2177 Block Diagram.” The ratio of R1 to R2
determines the output voltage. To optimize efficiency
during low output current operation, R2 should not be
less than 20k ? . However, to prevent feedback error due
to input bias current at the FB pin, R2 should not be
greater than 100k ? . After selecting R2, calculate R1
using the following formula:
? ? V OUT ? ?
? ? 1.245V ? ?
MIC2177
increase significantly. Both of these effects will degrade
efficiency. The formula for peak inducto rcurrent is:
I L(peak) = I LOAD(max) + 300mA
To maximize efficiency, the inductor’s resistance must
be less than the output switch on-resistance (preferably
50m ? or less).
Output Capacitor Selection
Select an output capacitor that has a low value of ESR.
This parameter determines a regulator’s output ripple
voltage (V RIPPLE ) which is generated by ? I L × ESR. As
mentioned in “Inductor Selection,” the maximum value
for ? I L is 600mA.
Therefore, the maximum value of ESR is:
Input Capacitor Selection
The input capacitor is selected for its RMS current and
voltage rating and should be a low ESR (equivalent
Where:
ESR MAX =
600mA
V RIPPLE
series resistance) electrolytic or tantalum capacitor. As a
rule-of-thumb, the voltage rating for a tantalum capacitor
should be twice the value of V IN , and the voltage rating
for an electrolytic should be 40% higher than V IN . The
RMS current rating must be equal or greater than the
maximum RMS input ripple current. A simple, worst-case
formula for calculating this RMS current is:
V RIPPLE < 1% of V OUT
Typically, capacitors in the range of 100μF to 220μF
have ESR less than this maximum value. The output
capacitor can be either a low ESR electrolytic or
tantalum capacitor, but tantalum is a better choice for
compact layout and operation at temperatures below
0°C. The voltage rating of a tantalum capacitor must be
I RMS(max) =
I LOAD(max)
2
2 × V OUT , and the voltage rating of an electrolytic must
be 1.4 × V OUT .
Tantalum capacitors are a better choice for applications
that require the most compact layout or operation below
0°C. The input capacitor must be located very close to
the V IN pin (within 0.2 inches, 5mm). Also place a 0.1μF
ceramic bypass capacitor as close as possible to V IN .
Inductor Selection
The inductor must be at least a minimum value in order
for the MIC2177 to change from PWM to skip mode at
the correct value of output current. This minimum value
ensures the inductor ripple current never exceeds
600mA, and is calculated using the following formula:
Output Diode Selection
In PWM operation, inductor current flows through the
output diode approximately 50ns during the dead time
when one output MOSFET turns off and the other turns
on. In skip-mode, the inductor current flows through the
diode during the entire P-channel off time. The correct
diode for both of these conditions is a 1A diode with a
reverse voltage rating greater than V IN . It must be a
Schottky or ultra fast-recovery diode (t R <100ns) to
minimize power dissipation from the diode’s reverse-
recovery charge.
L MIN = V OUT ? 1 ?
?
? × 8.3 μ .3 μ
?
?
?
V OUT
V IN(max)
?
?
Compensation
Compensation is provided by connecting a series RC
load to the COMP pin. This creates a pole-zero pair in
Where:
V IN(max) = maximum input voltage
In general, a value at least 20% greater than L MIN should
be selected because inductor values have a tolerance of
±20%.
Two other parameters to consider in selecting an
inductor are winding resistance and peak current rating.
The inductor must have a peak current rating equal or
greater than the peak inductor current. Otherwise, the
inductor may saturate, causing excessive current in the
output switch. Also, the inductor’s core loss may
the regulator control loop, allowing the regulator to
remain stable with enough low frequency loop-gain for
good load and line regulation. At higher frequencies
pole-zero reduces loop-gain to a level referred to as the
mid-band gain. The mid-band gain is low enough so that
the loop gain crosses 0dB with sufficient phase margin.
Typical values for the RC load are 4.7nF – 10nF for the
capacitor and 5k ? – 20k ? for the resistor.
Printed Circuit Board Layout
A well designed PC board will prevent switching noise
and ground bounce from interfering with the operation of
April 2008
13
M9999-042108
相关PDF资料 |
PDF描述 |
|---|---|
| MIC2178BWM TR | IC REG BUCK SYNC ADJ 2.5A 20SOIC |
| MIC2179BSM TR | IC REG BUCK SYNC ADJ 1.5A 20SSOP |
| MIC2182-3.3YM | IC REG CTRLR BUCK PWM CM 16-SOIC |
| MIC2183BQS TR | IC REG CTRLR BUCK PWM CM 16-QSOP |
| MIC2184YQS | IC REG CTRLR BUCK PWM CM 16-QSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2177YWM | 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 |
| MIC2177YWM 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 |
| MIC2177YWM-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 1.245V 1 Output 2.5A 20-SOIC (0.295", 7.50mm 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:2.5A 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-SOIC（0.295"，7.50mm 宽） 供应商器件封装:20-SOIC W 标准包装:1 |
| MIC2178 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2.5A Synchronous Buck Regulator |
| MIC2178_05 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2.5A Synchronous Buck Regulator |
发布紧急采购，3分钟左右您将得到回复。