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參數(shù)資料
| 型號： | mic5205 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | 150mA Low-Noise LDO Regulator(輸出電流150mA低噪聲低壓差穩(wěn)壓器) |
| 中文描述： | 150mA低噪聲LDO穩(wěn)壓器（輸出電流為150mA低噪聲低壓差穩(wěn)壓器） |
| 文件頁數(shù)： | 7/12頁 |
| 文件大小： | 81K |
| 代理商： | MIC5205 |
MIC5205
Micrel
June 2000
7
MIC5205
Applications Information
Enable/Shutdown
Forcing EN (enable/shutdown) high (> 2V) enables the regu-
lator. EN is compatible with CMOS logic gates.
If the enable/shutdown feature is not required, connect EN
Input Capacitor
A 1
μ
F capacitor should be placed from IN to GND if there is
more than 10 inches of wire between the input and the ac filter
capacitor or if a battery is used as the input.
Reference Bypass Capacitor
BYP (reference bypass) is connected to the internal voltage
reference. A 470pF capacitor (C
BYP
) connected from BYP to
GND quiets this reference, providing a significant reduction in
output noise. C
BYP
reduces the regulator phase margin;
when using C
BYP
, output capacitors of 2.2
μ
F or greater are
generally required to maintain stability.
The start-up speed of the MIC5205 is inversely proportional
to the size of the reference bypass capacitor. Applications
requiring a slow ramp-up of output voltage should consider
larger values of C
BYP
. Likewise, if rapid turn-on is necessary,
consider omitting C
BYP
.
If output noise is not a major concern, omit C
BYP
and leave
BYP open.
Output Capacitor
An output capacitor is required between OUT and GND to
prevent oscillation. The minimum size of the output capacitor
is dependent upon whether a reference bypass capacitor is
used. 1.0
μ
F minimum is recommended when C
BYP
is not
used (see Figure 2). 2.2
μ
F minimum is recommended when
C
BYP
is 470pF (see Figure 1). Larger values improve the
regulator
’
s transient response. The output capacitor value
may be increased without limit.
The output capacitor should have an ESR (effective series
resistance) of about 5
or less and a resonant frequency
above 1MHz. Ultra-low-ESR capacitors can cause a low
amplitude oscillation on the output and/or underdamped
transient response. Most tantalum or aluminum electrolytic
capacitors are adequate; film types will work, but are more
expensive. Since many aluminum electrolytics have electro-
lytes that freeze at about
–
30
°
C, solid tantalums are recom-
mended for operation below
–
25
°
C.
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.47
μ
F for current below 10mA or 0.33
μ
F for currents below
1mA.
No-Load Stability
The MIC5205 will remain stable and in regulation with no load
(other than the internal voltage divider) unlike many other
voltage regulators. This is especially important in CMOS
RAM keep-alive applications.
Thermal Considerations
The MIC5205 is designed to provide 150mA of continuous
current in a very small package. Maximum power dissipation
can be calculated based on the output current and the voltage
drop across the part. To determine the maximum power
dissipation of the package, use the junction-to-ambient ther-
mal resistance of the device and the following basic equation:
(
θ
P
=
T
–
T
D(max)
J(max)
A
JA
)
T
J(max)
is the maximum junction temperature of the die,
125
°
C, and T
A
is the ambient operating temperature.
θ
JA
is
layout dependent; Table 1 shows examples of junction-to-
ambient thermal resistance for the MIC5205.
Package
θ
JA
Recommended
Minimum Footprint
θ
JA
1" Square
Copper Clad
θ
JC
SOT-23-5 (M5)
220
°
C/W
170
°
C/W
130
°
C/W
Table 1. SOT-23-5 Thermal Resistance
The actual power dissipation of the regulator circuit can be
determined using the equation:
P
D
= (V
IN
–
V
OUT
) I
OUT
+ V
IN
I
GND
Substituting P
D(max)
for P
D
and solving for the operating
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit. For
example, when operating the MIC5205-3.3BM5 at room
temperature with a minimum footprint layout, the maximum
input voltage for a set output current can be determined as
follows:
°
220
P
D(max)
= 455mW
The junction-to-ambient thermal resistance for the minimum
footprint is 220
°
C/W, from Table 1. The maximum power
dissipation must not be exceeded for proper operation. Using
the output voltage of 3.3V and an output current of 150mA,
the maximum input voltage can be determined. From the
Electrical Characteristics table, the maximum ground current
for 150mA output current is 2500
μ
A or 2.5mA.
455mW = (V
IN
–
3.3V) 150mA + V
IN
·
2.5mA
455mW = V
IN
·
150mA
–
495mW + V
IN
·
2.5mA
950mW = V
IN
·
152.5mA
V
IN(max)
= 6.23V
Therefore, a 3.3V application at 150mA of output current can
accept a maximum input voltage of 6.2V in a SOT-23-5
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 Regu-
latorshandbook.
P
= 125 C
–
25 C
C/W
D(max)
°
)
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相關代理商/技術參數(shù) |
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|---|---|
| MIC5205_06 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:150mA Low-Noise LDO Regulator |
| MIC5205-1.5BM5 | 制造商:Exar Corporation 功能描述:VOLTAGE REGULATOR |
| MIC5205-1.88BM5TR | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel 制造商:RF Micro Devices Inc 功能描述: 制造商:Micrel Inc 功能描述: |
| MIC5205-1.8BM5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MIC5205-2.5BM5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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