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MIC29300-5.0BU 参数 Datasheet PDF下载

MIC29300-5.0BU图片预览
型号: MIC29300-5.0BU
PDF下载: 下载PDF文件 查看货源
内容描述: 高电流低压差稳压器 [High-Current Low-Dropout Regulators]
分类和应用: 线性稳压器IC调节器电源电路输出元件
文件页数/大小: 20 页 / 134 K
品牌: MICREL [ MICREL SEMICONDUCTOR ]
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MIC29150/29300/29500/29750  
Micrel  
First, we calculate the power dissipation of the regulator from  
thesenumbersandthedeviceparametersfromthisdatasheet.  
Applications Information  
The MIC29150/29300/29500/29750 are high performance  
low-dropout voltage regulators suitable for all moderate to  
high-current voltage regulator applications. Their 300mV to  
400mV dropout voltage at full load make them especially  
valuable in battery powered systems and as high efficiency  
noise filters in post-regulatorapplications. Unlike older  
NPN-pass transistor designs, where the minimum dropout  
voltage is limited by the base-emitter voltage drop and  
collector-emitter saturation voltage, dropout performance of  
the PNP output of these devices is limited merely by the low  
P = I  
1.01V V  
(
IN  
OUT  
)
D
OUT  
Where the ground current is approximated by 1% of I  
.
OUT  
Then the heat sink thermal resistance is determined with this  
formula:  
T
T  
A
J MAX  
θ
=
− θ + θ  
(
)
SA  
JC  
CS  
P
D
Where T  
125°C and θ is between 0 and 2°C/W.  
CS  
J MAX  
V
saturation voltage.  
CE  
The heat sink may be significantly reduced in applications  
where the minimum input voltage is known and is large  
compared with the dropout voltage. Use a series input  
resistor to drop excessive voltage and distribute the heat  
between this resistor and the regulator. The low dropout  
properties of Micrel Super ßeta PNP regulators allow very  
significant reductions in regulator power dissipation and the  
associated heat sink without compromising performance.  
When this technique is employed, a capacitor of at least  
0.1µF is needed directly between the input and regulator  
ground.  
A trade-off for the low dropout voltage is a varying base drive  
requirement. But Micrels Super ßeta PNPprocess re-  
ducesthisdriverequirementtomerely1%oftheloadcurrent.  
The MIC2915029750 family of regulators is fully protected  
from damage due to fault conditions. Current limiting is  
provided. Thislimitingislinear;outputcurrentunderoverload  
conditions is constant. Thermal shutdown disables the de-  
vice when the die temperature exceeds the 125°C maximum  
safe operating temperature. Transient protection allows de-  
vice (and load) survival even when the input voltage spikes  
between 20V and +60V. When the input voltage exceeds  
about 35V to 40V, the overvoltage sensor temporarily dis-  
ables the regulator. The output structure of these regulators  
allows voltages in excess of the desired output voltage to be  
appliedwithoutreversecurrentflow.MIC29xx1andMIC29xx2  
versions offer a logic level ON/OFF control: when disabled,  
the devices draw nearly zero current.  
Please refer to Application Note 9 and Application Hint 17 for  
further details and examples on thermal design and heat sink  
specification.  
Capacitor Requirements  
For stability and minimum output noise, a capacitor on the  
regulator output is necessary. The value of this capacitor is  
dependent upon the output current; lower currents allow  
smaller capacitors. MIC2915029750 regulators are stable  
with the following minimum capacitor values at full load:  
An additional feature of this regulator family is a common  
pinout: a designs current requirement may change up or  
downyetusethesameboardlayout,asalloftheseregulators  
have identical pinouts.  
Device  
Full Load Capacitor  
VOUT  
VIN  
OUT  
IN  
MIC29150.............................. 10µF  
MIC29300.............................. 10µF  
MIC29500.............................. 10µF  
MIC29750.............................. 22µF  
GND  
This capacitor need not be an expensive low ESR type:  
aluminum electrolytics are adequate. In fact, extremely low  
ESR capacitors may contribute to instability. Tantalum ca-  
pacitors are recommended for systems where fast load  
transient response is important.  
Figure 3. Linear regulators require only two capacitors  
for operation.  
Thermal Design  
Linear regulators are simple to use. The most complicated  
design parameters to consider are thermal characteristics.  
Thermal design requires the following application-specific  
parameters:  
Where the regulator is powered from a source with a high AC  
impedance, a 0.1µF capacitor connected between Input and  
GND is recommended. This capacitor should have good  
characteristics to above 250kHz.  
Maximum ambient temperature, T  
A
Output Current, I  
Minimum Load Current  
OUT  
Output Voltage, V  
The MIC2915029750 regulators are specified between fi-  
nite loads. If the output current is too small, leakage currents  
dominate and the output voltage rises. The following mini-  
mum load current swamps any expected leakage current  
across the operating temperature range:  
OUT  
Input Voltage, V  
IN  
MIC29150/29300/29500/29750  
14  
March 2000