- 您现在的位置：买卖IC网 > PDF目录14463 > MIC2179-3.3YSM (Micrel Inc)IC REG BUCK SYNC 3.3V 20SSOP PDF资料下载
参数资料
| 型号： | MIC2179-3.3YSM |
| 厂商： | Micrel Inc |
| 文件页数： | 11/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC 3.3V 20SSOP |
| 标准包装： | 67 |
| 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： | 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 |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-1711-5 MIC2179-3.3YSM-ND |
R1 = R2 ((
) -1 )
?I L(max)
I RMS(max) =
I L(peak) = I LOAD(max) +
?I L(max) = V OUT ( 1 -
) x
Micrel, Inc.
Application Information
Feedback Resistor Selection (Adjustable Version)
The output voltage is programmed by connecting an external
resistive divider to the FB pin as shown in “MIC2179 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 20kΩ. However, to prevent feedback
error due to input bias current at the FB pin, R2 should not
be greater than 100kΩ. After selecting R2, calculate R1 with
the following formula:
V OUT
1.245V
Input Capacitor Selection
The input capacitor is selected for its RMS current and voltage
rating and should be a low ESR (equivalent 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 cur-
rent. A simple, worst case formula for calculating this RMS
current is:
I LOAD(max)
2
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 VIN
pin (within 0.2in, 5mm). Also, place a 0.1μF ceramic bypass
capacitor as close as possible to VIN.
Inductor Selection
The MIC2179 is a current-mode controller with internal slope
compensation. As a result, the inductor must be at least a
minimum value to prevent subharmonic oscillations. This
minimum value is calculated by the following formula:
L MIN = V OUT x 3.0 μH/V
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 satu-
rate, causing excessive current in the output switch. Also,
the inductor ’s core loss may increase significantly. Both of
these effects will degrade efficiency. The formula for peak
inductor current is:
?I L(max)
2
Where:
V OUT 1
V IN(max) L ? f
MIC2179
To maximize efficiency, the inductor ’s resistance must
be less than the output switch on-resistance (preferably,
50mΩ or less).
Output Capacitor Selection
Select an output capacitor that has a low value of ESR.
This parameter determines a regulator ’s output ripple volt-
age (V RIPPLE ) which is generated by ? I L × ESR. Therefore,
ESR must be equal or less than a maximum value calculated
for a specified V RIPPLE (typically less than 1% of the output
voltage) and ? I L(max) :
V RIPPLE
ESR MAX =
Typically, capacitors in the range of 100 to 220μF have ESR
less than this maximum value. The output capacitor can be
a low ESR electrolytic or tantalum capacitor, but tantalum is
a better choice for compact layout and operation at tempera-
tures below 0°C. The voltage rating of a tantalum capacitor
must be 2 × V OUT , and the voltage rating of an electrolytic
must be 1.4 × V OUT .
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 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 condi-
tions is a 1A diode with a reverse voltage rating greater than
V IN . It must be a schottky or ultrafast-recovery diode
(t R < 100ns) to minimize power dissipation from the diode’s
reverse-recovery charge.
Compensation
Compensation is provided by connecting a series RC load
to the COMP pin. This creates a pole-zero pair in the regu-
lator control loop, allowing the regulator to remain stable
with enough low frequency loop-gain for good load and line
regulation. At higher frequencies, the 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 to 10nF for the capacitor and 5kΩ to 20kΩ
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 the
MIC2179. A good design takes into consideration component
placement and routing of power traces.
The first thing to consider is the locations of the input ca -
pacitor, inductor, output diode, and output capacitor. The
input capacitor must be placed very close to the VIN pin,
the inductor and output diode very close to the SW pin, and
the output capacitor near the inductor. These components
pass large high-frequency current pulses, so they must use
short, wide power traces. In addition, their ground pins and
PGND are connected to a ground plane that is nearest the
power supply ground bus.
June 2009
11
M9999-063009
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3642IDD#PBF | IC REG BUCK SYNC ADJ 50MA 8DFN |
| RGM15DTMD-S189 | CONN EDGECARD 30POS R/A .156 SLD |
| LT3973IDD-5#PBF | IC REG BUCK 5V 0.75A 10DFN |
| LT1073CS8#PBF | IC REG BUCK BOOST INV ADJ 8SOIC |
| VE-BWD-EX-F2 | CONVERTER MOD DC/DC 85V 75W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2179-5.0BSM | 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 |
| MIC2179-5.0BSM 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 |
| MIC2179-5.0YSM | 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 |
| MIC2179-5.0YSM 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 |
| MIC2179-5.0YSMTR | 制造商:RF Micro Devices Inc 功能描述: |
发布紧急采购，3分钟左右您将得到回复。