LM3915
LM3915 Dot/Bar Display Driver
Literature Number: SNVS740B
LM3915
Dot/Bar Display Driver General Description
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The LM3915is a monolithic integrated circuit that ns analog voltage levels and drives ten LEDs,LCDs or vacuum fluorescent displays,providing a logarithmic3dB/step ana-log display.One pin changes the display from a bar graph to a moving dot display.LED current drive is regulated and programmable,eliminating the need for current limiting re-sistors.The whole display system can operate from a single supply as low as3V or as high as25V.
The IC contains an adjustable voltage reference and an accurate ten-step voltage divider.The high-impedance input buffer accepts signals down to ground and up to within1.5V of the positive supply.Further,it needs no protection against inputs of±35V.The input buffer drives10individual com-parators referenced to the precision divider.Accuracy is typically better than1dB.
The LM3915’s3dB/step display is suited for signals with wide dynamic range,such as audio level,power,light inten-sity or vibration.Audio applications include average or peak level indicators,power meters and RF signal strength meters.Replacing conventional meters with an LED bar graph results in a faster responding,more rugged display with high visibility that retains the ea of interpretation of an analog display.
o型腿怎么矫正The LM3915is extremely easy to apply.A1.2V full-scale meter requires only one resistor in addition t
o the ten LEDs. One more resistor programs the full-scale anywhere from 1.2V to12V independent of supply voltage.LED brightness is easily controlled with a single pot.The LM3915is very versatile.The outputs can drive LCDs, vacuum fluorescents and incandescent bulbs as well as LEDs of any color.Multiple devices can be cascaded for a dot or bar mode display with a range of60or90dB. LM3915s can also be cascaded with LM3914s for a linear/ log display or with LM3916s for an extended-range VU meter.
Features
n3dB/step,30dB range
n Drives LEDs,LCDs,or vacuum fluorescents
n Bar or dot display mode externally lectable by ur
n Expandable to displays of90dB
n Internal voltage reference from1.2V to12V
n Operates with single supply of3V to25V
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n Inputs operate down to ground
n Output current programmable from1mA to30mA
n Input withstands±35V without damage or fal outputs n Outputs are current regulated,open collectors
n Directly drives TTL or CMOS
n The internal10-step divider is floating and can be referenced to a wide range of voltages
The LM3915is rated for operation from0˚C to+70˚C.The LM3915N-1is available in an18-lead molded DIP package.
©2004National Semiconductor Corporation
0V to10V Log Display
00510 Notes:Capacitor C1is required if leads to the LED supply are6"or longer.
Circuit as shown is wired for dot mode.For bar mode,connect pin9to pin3.V LED must be kept below7V or dropping resistor should be ud to limit I dissipation.
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plea contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Power Dissipation(Note6)
动物世界李易峰Molded DIP(N)1365mW Supply Voltage25V Voltage on Output Drivers25V Reference Load Current10mA Storage Temperature Range−55˚C to+150˚C Lead Temperature
(Soldering,10c.)260˚C
Electrical Characteristics(Notes2,4)
Parameter Conditions(Note2)Min Typ Max Units COMPARATOR
Offt Voltage,Buffer and First Comparator 0V≤V RLO=V RHI≤12V,
I LED=1mA
310mV
Offt Voltage,Buffer and Any Other Comparator 0V≤V RLO=V RHI≤12V,
I LED=1mA
315mV
Gain(∆I LED/∆V IN)I L(REF)=2mA,I LED=10mA38mA/mV Input Bias Current(at Pin5)0V≤V IN≤(V+−1.5V)25100nA Input Signal Overvoltage No Change in Display−3535V VOLTAGE-DIVIDER
Divider Resistance Total,Pin6to4162836kΩ
Relative Accuracy(Input Change Between Any Two Threshold Points)(Note3)
2.0
3.0
4.0dB
Absolute Accuracy at Each Threshold
Point
(Note3)
V IN=−3,−6dB−0.5+0.5dB
V IN=−9dB−0.5+0.65dB
V IN=−12,−15,−18dB−0.5+1.0dB
V IH=−21,−24,−27dB−0.5+1.5dB VOLTAGE REFERENCE
Output Voltage0.1mA≤I L(REF)≤4mA,
V+=V LED=5V
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1.2 1.28 1.34V Line Regulation3V≤V+≤18V0.010.03%/V Load Regulation0.1mA≤I L(REF)≤4mA,
V+=V LED=5V
0.42%
o2o闭环模式Output Voltage Change with Temperature 0˚C≤T A≤+70˚C,I L(REF)=1mA,
V+=V LED=5V
索虏1%
Adjust Pin Current75120µA OUTPUT DRIVERS
LED Current V+=V LED=5V,I L(REF)=1mA71013mA
LED Current Difference(Between Largest and Smallest LED Currents)V LED=5V,I LED=2mA
V LED=5V,I LED20mA
0.120.4
mA
1.23
LED Current Regulation2V≤V LED≤17V,I LED=2mA
I LED=20mA 0.10.25
mA 13
Dropout Voltage I LED(ON)=20mA,@V LED=5V,
∆I LED=2mA 1.5V Saturation Voltage I LED=2.0mA,I L(REF)=0.4mA0.150.4V Output Leakage,Each Collector(Bar Mode)(Note5)0.110µA
Output Leakage Pins10–18(Dot Mode)(Note5)
0.110µA
Pin160150450µA
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SUPPLY CURRENT
Standby Supply Current (All Outputs Off)V+=+5V,I L(REF)=0.2mA
V+=+20V,I L(REF)=1.0mA
辣木树
2.4 4.2
6.19.2
Note1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating Ratings indicate conditions for which the functional,but do not guarantee specific performance limits.Electrical Characteristics state DC and AC electrical specifications under particular test conditio guarantee specific performance limits.This assumes that the device is within the Operating Ratings.Specifications are not guaranteed for parameters where is given,however,the typical value is a good indication of device performance.
Note2:Unless otherwi stated,all specifications apply with the following conditions:
3V DC≤V+≤20V DC−0.015V≤V RLO≤12V DC T A=25˚C,I L(REF)=0.2mA,pin9connected to pin3(bar mode).
3V DC≤V LED≤V+V REF,V RHI,V RLO≤(V+−1.5V)For higher power dissipations,pul testing is ud.
−0.015V≤V RHI≤12V DC0V≤V IN≤V+−1.5V
Note3:Accuracy is measured referred to0dB=+10.000V DC at pin5,with+10.000V DC at pin6,and0.000V DC at pin4.At lower full scale voltages,b comparator offt voltage may add significant error.See table for threshold voltages.
Note4:Pin5input current must be limited to±3mA.The addition of a39k resistor in ries with pin5allows±100V signals without damage.
Note5:Bar mode results when pin9is within20mV of V+.Dot mode results when pin9is pulled at least200mV below V+.LED#10(pin10output cu disabled if pin9is pulled0.9V or more below V LED.
Note6:The maximum junction temperature of the LM3915is100˚C.Devices must be derated for operation at elevated temperatures.Junction to ambien resistance is55˚C/W for the molded DIP(N pa
ckage).
Threshold Voltage(Note3)
Output dB Min Typ Max Output dB Min Typ 1−270.4220.4470.5316−12 2.372 2.5122 2−240.5960.6310.7507−9 3.350 3.5483 3−210.8410.891 1.0598−6 4.732 5.0125 4−18 1.189 1.259 1.4139−3 6.6837.0797 5−15 1.679 1.778 1.9951009.985101
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