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LT1763CS8-2.5#TRPBF 参数 Datasheet PDF下载

LT1763CS8-2.5#TRPBF图片预览
型号: LT1763CS8-2.5#TRPBF
PDF下载: 下载PDF文件 查看货源
内容描述: [LT1763 - 500mA, Low Noise, LDO Micropower Regulators; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C]
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: 16 页 / 280 K
品牌: Linear [ Linear ]
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LT1763 Series  
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PIN FUNCTIONS  
Note that the voltage drop across the external PC traces  
willaddtothedropoutvoltageoftheregulator. TheSENSE  
pin bias current is 10µA at the nominal rated output  
voltage. The SENSE pin can be pulled below ground (as in  
a dual supply system where the regulator load is returned  
to a negative supply) and still allow the device to start and  
operate.  
SHDN (Pin 5): Shutdown. The SHDN pin is used to put the  
LT1763 regulators into a low power shutdown state. The  
output will be off when the SHDN pin is pulled low. The  
SHDN pin can be driven either by 5V logic or open-  
collector logic with a pull-up resistor. The pull-up resistor  
is required to supply the pull-up current of the open-  
collector gate, normally several microamperes, and the  
SHDN pin current, typically 1µA. If unused, the SHDN pin  
must be connected to VIN. The device will be in the low  
power shutdown state if the SHDN pin is not connected.  
ADJ (Pin 2): Adjust. For the adjustable LT1763, this is the  
input to the error amplifier. This pin is internally clamped  
to ±7V. It has a bias current of 30nA which flows into the  
pin (see curve of ADJ Pin Bias Current vs Temperature in  
theTypicalPerformanceCharacteristicssection).TheADJ  
pin voltage is 1.22V referenced to ground and the output  
voltage range is 1.22V to 20V.  
IN (Pin 8): Input. Power is supplied to the device through  
the IN pin. A bypass capacitor is required on this pin if the  
device is more than six inches away from the main input  
filter capacitor. In general, the output impedance of a  
battery rises with frequency, so it is advisable to include a  
bypass capacitor in battery-powered circuits. A bypass  
capacitor in the range of 1µF to 10µF is sufficient. The  
LT1763 regulators are designed to withstand reverse  
voltages on the IN pin with respect to ground and the OUT  
pin. In the case of a reverse input, which can happen if a  
battery is plugged in backwards, the device will act as if  
there is a diode in series with its input. There will be no  
reverse current flow into the regulator and no reverse  
voltage will appear at the load. The device will protect both  
itself and the load.  
BYP (Pin 4): Bypass. The BYP pin is used to bypass the  
reference of the LT1763 regulators to achieve low noise  
performance from the regulator. The BYP pin is clamped  
internally to ±0.6V (one VBE). A small capacitor from the  
output to this pin will bypass the reference to lower the  
output voltage noise. A maximum value of 0.01µF can be  
usedforreducingoutputvoltagenoisetoatypical20µVRMS  
over a 10Hz to 100kHz bandwidth. If not used, this pin  
must be left unconnected.  
GND (Pins 3, 6, 7): Ground.  
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APPLICATIONS INFORMATION  
TheLT1763seriesare500mAlowdropoutregulatorswith  
micropowerquiescentcurrentandshutdown.Thedevices  
are capable of supplying 500mA at a dropout voltage of  
300mV. Output voltage noise can be lowered to 20µVRMS  
over a 10Hz to 100kHz bandwidth with the addition of a  
0.01µFreferencebypasscapacitor. Additionally, therefer-  
ence bypass capacitor will improve transient response of  
the regulator, lowering the settling time for transient load  
conditions. The low operating quiescent current (30µA)  
drops to less than 1µA in shutdown. In addition to the low  
quiescentcurrent, theLT1763regulatorsincorporatesev-  
eral protection features which make them ideal for use in  
battery-powered systems. The devices are protected  
against both reverse input and reverse output voltages. In  
battery backup applications where the output can be held  
up by a backup battery when the input is pulled to ground,  
the LT1763-X acts like it has a diode in series with its  
output and prevents reverse current flow. Additionally, in  
dual supply applications where the regulator load is re-  
turnedtoanegativesupply,theoutputcanbepulledbelow  
groundbyasmuchas20Vandstillallowthedevicetostart  
and operate.  
Adjustable Operation  
The adjustable version of the LT1763 has an output  
voltage range of 1.22V to 20V. The output voltage is set by  
theratiooftwoexternalresistorsasshowninFigure2.The  
device servos the output to maintain the ADJ pin voltage  
at 1.22V referenced to ground. The current in R1 is then  
equalto1.22V/R1andthecurrentinR2isthecurrentinR1  
1763fa  
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