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MIC39100-3.3BS 参数 Datasheet PDF下载

MIC39100-3.3BS图片预览
型号: MIC39100-3.3BS
PDF下载: 下载PDF文件 查看货源
内容描述: 1A低压低压降稳压器 [1A Low-Voltage Low-Dropout Regulator]
分类和应用: 线性稳压器IC调节器电源电路光电二极管输出元件
文件页数/大小: 12 页 / 104 K
品牌: MICREL [ MICREL SEMICONDUCTOR ]
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MIC39100/39101/39102  
Micrel  
Input Capacitor  
Applications Information  
An input capacitor of 1µF or greater is recommended when  
thedeviceismorethan4inchesawayfromthebulkacsupply  
capacitance or when the supply is a battery. Small, surface  
mount, ceramic chip capacitors can be used for bypassing.  
Larger values will help to improve ripple rejection by bypass-  
ing the input to the regulator, further improving the integrity of  
the output voltage.  
The MIC39100/1/2 is a high-performance low-dropout volt-  
age regulator suitable for moderate to high-current voltage  
regulator applications. Its 630mV dropout voltage at full load  
and overtemperature makes it especially valuable in battery-  
powered systems and as high-efficiency noise filters in post-  
regulator applications. Unlike older NPN-pass transistor de-  
signs, where the minimum dropout voltage is limited by the  
base-to-emitter voltage drop and collector-to-emitter satura-  
tion voltage, dropout performance of the PNP output of these  
Error Flag  
The MIC39101 features an error flag (FLG), which monitors  
the output voltage and signals an error condition when this  
voltage drops 5% below its expected value. The error flag is  
an open-collector output that pulls low under fault conditions  
and may sink up to 10mA. Low output voltage signifies a  
number of possible problems, including an overcurrent fault  
(the device is in current limit) or low input voltage. The flag  
output is inoperative during overtemperature conditions. A  
devices is limited only by the low V saturation voltage.  
CE  
A trade-off for the low dropout voltage is a varying base drive  
requirement. Micrels Super βeta PNPprocess reduces  
this drive requirement to only 2% of the load current.  
The MIC39100/1/2 regulator is fully protected from damage  
due to fault conditions. Linear current limiting is provided.  
Output current during overload conditions is constant. Ther-  
mal shutdown disables the device when the die temperature  
exceeds the maximum safe operating temperature. Tran-  
sient protection allows device (and load) survival even when  
the input voltage spikes above and below nominal. The  
outputstructureoftheseregulatorsallowsvoltagesinexcess  
of the desired output voltage to be applied without reverse  
current flow.  
pull-up resistor from FLG to either V or V  
is required for  
IN  
OUT  
properoperation.Forinformationregardingtheminimumand  
maximum values of pull-up resistance, refer to the graph in  
the typical characteristics section of the data sheet.  
Enable Input  
The MIC39101 and MIC39102 versions feature an active-  
high enable input (EN) that allows on-off control of the  
regulator. Current drain reduces to zerowhen the device is  
shutdown, with only microamperes of leakage current. The  
EN input has TTL/CMOS compatible thresholds for simple  
MIC39100-x.x  
VIN  
VOUT  
IN  
OUT  
GND  
logic interfacing. EN may be directly tied to V and pulled up  
CIN  
COUT  
IN  
to the maximum supply voltage  
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V  
Conversion  
Figure 1. Capacitor Requirements  
Output Capacitor  
The MIC39100/1/2 has excellent transient response to varia-  
tions in input voltage and load current. The device has been  
designed to respond quickly to load current variations and  
input voltage variations. Large output capacitors are not  
required to obtain this performance. A standard 10µF output  
capacitor, preferably tantalum, is all that is required. Larger  
values help to improve performance even further.  
The MIC39100/1/2 requires an output capacitor to maintain  
stability and improve transient response. Proper capacitor  
selection is important to ensure proper operation. The  
MIC39100/1/2 output capacitor selection is dependent upon  
theESR(equivalentseriesresistance)oftheoutputcapacitor  
to maintain stability. When the output capacitor is 10µF or  
greater, the output capacitor should have an ESR less than  
2. This will improve transient response as well as promote  
stability. Ultra-low-ESR capacitors (<100m), such as ce-  
ramic chip capacitors, may promote instability. These very  
low ESR levels may cause an oscillation and/or underdamp-  
ed transient response. A low-ESR solid tantalum capacitor  
works extremely well and provides good transient response  
and stability over temperature. Aluminum electrolytics can  
also be used, as long as the ESR of the capacitor is <2.  
By virtue of its low-dropout voltage, this device does not  
saturate into dropout as readily as similar NPN-based de-  
signs. Whenconvertingfrom3.3Vto2.5Vor2.5Vto1.8V, the  
NPN based regulators are already operating in dropout, with  
typical dropout requirements of 1.2V or greater. To convert  
down to 2.5V or 1.8V without operating in dropout, NPN-  
based regulators require an input voltage of 3.7V at the very  
least. The MIC39100 regulator will provide excellent perfor-  
mance with an input as low as 3.0V or 2.5V respectively. This  
gives the PNP based regulators a distinct advantage over  
older, NPN based linear regulators.  
The value of the output capacitor can be increased without  
limit. Higher capacitance values help to improve transient  
response and ripple rejection and reduce output noise.  
Minimum Load Current  
TheMIC39100/1/2regulatorisspecifiedbetweenfiniteloads.  
If the output current is too small, leakage currents dominate  
and the output voltage rises. A 10mA minimum load current  
is necessary for proper regulation.  
June 2000  
9
MIC39100/39101/39102