参数资料
型号: MIC5331-PPYMT TR
厂商: Micrel Inc
文件页数: 7/10页
文件大小: 0K
描述: IC REG LDO 3V .3A 8TMLF
标准包装: 1
稳压器拓扑结构: 正,固定式
输出电压: 3V
输入电压: 2.3 V ~ 5.5 V
电压 - 压降(标准): 0.12V @ 300mA
稳压器数量: 2
电流 - 输出: 300mA
电流 - 限制(最小): 350mA
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 8-VFDFN 裸露焊盘,8-MLF?
供应商设备封装: 8-MLF?(2x2)
包装: 标准包装
产品目录页面: 1104 (CN2011-ZH PDF)
其它名称: 576-3156-6
P D(MAX) = ? ?
? T J(MAX) ? T A ?
?
Micrel, Inc.
Application Information
MIC5331 is a tiny dual low quiescent current 300mA
LDO. The MIC5331 regulator is fully protected from
damage due to fault conditions, offering linear current
limiting and thermal shutdown.
Input Capacitor
The MIC5331 is a high-performance, high bandwidth
device. Therefore, it requires a well-bypassed input
supply for optimal performance. A 1μF capacitor is
required from the input to ground to provide stability.
Low-ESR ceramic capacitors provide optimal
performance at a minimum of space. Additional high-
frequency capacitors, such as small-valued NPO
dielectric-type capacitors, help filter out high-frequency
noise and are good practice in any RF-based circuit.
X5R or X7R dielectrics are recommended for the input
capacitor. Y5V dielectrics lose most of their capacitance
over temperature and are therefore, not recommended.
Output Capacitor
The MIC5331 requires an output capacitor of 1μF or
greater to maintain stability. The design is optimized for
use with low-ESR ceramic chip capacitors. High ESR
capacitors may cause high frequency oscillation. The
output capacitor can be increased, but performance has
been optimized for a 1μF ceramic output capacitor and
does not improve significantly with larger capacitance.
X7R/X5R dielectric-type ceramic capacitors are
recommended because of their temperature
performance. X7R-type capacitors change capacitance
by 15% over their operating temperature range and are
the most stable type of ceramic capacitors. Z5U and
Y5V dielectric capacitors change value by as much as
50% and 60%, respectively, over their operating
temperature ranges. To use a ceramic chip capacitor
with Y5V dielectric, the value must be much higher than
an X7R ceramic capacitor to ensure the same minimum
capacitance over the equivalent operating temperature
range.
No-Load Stability
Unlike many other voltage regulators, the MIC5331 will
remain stable and in regulation with no load. This is
especially important in CMOS RAM keep-alive
applications.
Enable/Shutdown
The MIC5331 comes with dual active-high enable pins
that allow each regulator to be disabled independently.
Forcing the enable pin low disables the regulator and
sends it into a “zero” off-mode-current state. In this state,
current consumed by the regulator goes nearly to zero.
Forcing the enable pin high enables the output voltage.
The active-high enable pin uses CMOS technology and
MIC5331
the enable pin cannot be left floating; a floating enable
pin may cause an indeterminate state on the output.
Thermal Considerations
The MIC5331 is designed to provide 300mA of
continuous current for both outputs in a very small
package. Maximum ambient operating temperature can
be calculated based on the output current and the
voltage drop across the part. For example if the input
voltage is 3.6V, the output voltage is 3.0V for V OUT1 , 2.8V
for V OUT2 and the output current = 300mA. The actual
power dissipation of the regulator circuit can be
determined using the equation:
P D = (V IN – V OUT1 ) I OUT1 + (V IN – V OUT2 ) I OUT2 + V IN I GND
Because this device is CMOS and the ground current is
typically <100μA over the load range, the power
dissipation contributed by the ground current is < 1%
and can be ignored for this calculation.
P D = (3.6V – 3.0V) × 300mA + (3.6V -2.8) × 300mA
P D = 0.42W
To determine the maximum ambient operating
temperature of the package, use the junction-to-ambient
thermal resistance of the device and the following basic
equation:
?
? θ JA ?
T J(max) = 125°C, and the maximum junction temperature
of the die, θ JA , thermal resistance = 90°C/W.
Substituting P D for P D(max) and solving for the ambient
operating temperature will give the maximum operating
conditions for the regulator circuit. The junction-to-
ambient thermal resistance for the minimum footprint is
90°C/W.
The maximum power dissipation must not be exceeded
for proper operation.
For example, when operating the MIC5331-PMYMT at
an input voltage of 3.6V and 300mA loads at each output
with a minimum footprint layout, the maximum ambient
operating temperature T A can be determined as follows:
0.42W = (125°C – T A )/(90°C/W)
T A = 87.2°C
Therefore, a 3.0V/2.8V application with 300mA at each
output current can accept an ambient operating
temperature of 87°C in a 2mm x 2mm MLF ? package.
For a full discussion of heat sinking and thermal effects
on voltage regulators, refer to the “Regulator Thermals”
section of Micrel’s Designing with Low-Dropout Voltage
Regulators handbook. This information can be found on
Micrel's website at:
http://www.micrel.com/_PDF/other/LDOBk_ds.pdf
February 2008
7
M9999-021408-A
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