参数资料
型号: MIC33050-SYHL TR
厂商: Micrel Inc
文件页数: 10/16页
文件大小: 0K
描述: IC REG BUCK SYNC 3.3V 0.6A 12MLF
产品培训模块: MIC23xxx HyperLight Load™ Regulators
标准包装: 1
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: 2.7 V ~ 5.5 V
PWM 型: 电流模式
频率 - 开关: 4MHz
电流 - 输出: 600mA
同步整流器:
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?(3x3)
产品目录页面: 1094 (CN2011-ZH PDF)
其它名称: 576-3353-6
Micrel, Inc.
Applications Information
MIC33050
Input Capacitor
A minimum of 2.2μF ceramic capacitor should be placed
close to the VIN pin and PGND pin for bypassing. X5R or
X7R dielectrics are recommended for the input capacitor.
Y5V dielectrics, aside from losing most of their
capacitance over temperature, they also become resistive
at high frequencies. This reduces their ability to filter out
100
90
80
Efficiency V OUT = 1.8V
V IN = 3.0V
70 V
high frequency noise.
Output Capacitor
60
IN
= 3.6V
V IN = 4.2V
The MIC33050 was designed for use with a 2.2μF or
1
greater ceramic output capacitor. A low equivalent series
resistance (ESR) ceramic output capacitor either X7R or
X5R is recommended. Y5V and Z5U dielectric capacitors,
aside from the undesirable effect of their wide variation in
50
10 100 1000
OUTPUT CURRENT (mA)
? ? ? 100
Efficiency (%) ? ? ? OUT
capacitance over temperature, become resistive at high
frequencies.
Compensation
The MIC33050 is designed to be stable with an internal
inductor with a minimum of 2.2μF ceramic (X5R) output
capacitor.
Efficiency Considerations
Efficiency is defined as the amount of useful output power,
divided by the amount of power supplied.
? V ? I OUT ?
? V IN ? I IN ?
Maintaining high efficiency serves two purposes. It
reduces power dissipation in the power supply, reducing
the need for heat sinks and thermal design considerations
and it reduces consumption of current for battery powered
applications. Reduced current draw from a battery
increases the devices operating time and is critical in hand
held devices.
The Figure above shows an efficiency curve. From 1μA to
100mA, efficiency losses are dominated by quiescent
current losses, gate drive and transition losses. By using
the HyperLight Load ? mode, the MIC33050 is able to
maintain high 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, thereby reducing the internal RDSON. 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 = I OUT2 × DCR
From that, the loss in efficiency due to inductor resistance
can be calculated as follows;
V OUT ? I OUT
Efficiency Loss (%) ? ? 1 ? ? ?
? ? ? ? 100
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
? ?
?
? ? V OUT ? I OUT ? L PD
? ?
? ? ?
high side MOSFET R DSON multiplied by the square of the
Switch Current. 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 4MHz frequency and the
switching transitions make up the switching losses.
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.
May 2012
10
M9999-050312-C
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