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LM3914

LM3914 Dot/Bar Display Driver

Literature Number: SNVS761A

LM3914 Dot/Bar Display Driver

February 2003

LM3914 Dot/Bar Display Driver
General Description
The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display. A single pin changes the display from a moving dot to a bar graph. Current drive to theLEDs is regulated and programmable, eliminating the need for resistors. This feature is one that allows operation of the whole system from less than 3V. The circuit contains its own adjustable reference and accurate 10-step voltage divider. The low-bias-current input buffer accepts signals down to ground, or V−, yet needs no protection against inputs of 35V above or below ground. The bufferdrives 10 individual comparators referenced to the precision divider. Indication non-linearity can thus be held typically to 1⁄2%, even over a wide temperature range. Versatility was designed into the LM3914 so that controller, visual alarm, and expanded scale functions are easily added on to the display system. The circuit can drive LEDs of many colors, or low-current incandescent lamps. Many LM3914scan be “chained” to form displays of 20 to over 100 segments. Both ends of the voltage divider are externally available so that 2 drivers can be made into a zero-center meter. The LM3914 is very easy to apply as an analog meter circuit. A 1.2V full-scale meter requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1 resistor is a pot, it becomes the LEDbrightness control. The simplified block diagram illustrates this extremely simple external circuitry. When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is avoided. Various novel displays are possible. Much of the display flexibility derives from the fact that alloutputs are individual, DC regulated currents. Various effects can be achieved by modulating these currents. The individual outputs can drive a transistor as well as a LED at the same time, so controller functions including “staging” control can be performed. The LM3914 can also act as a programmer, or sequencer. The LM3914 is rated for operation from 0˚C to +70˚C. The LM3914N-1 is available in an18-lead molded (N) package. The following typical application illustrates adjusting of the reference to a desired value, and proper grounding for accurate operation, and avoiding oscillations.

Features
Drives LEDs, LCDs or vacuum fluorescents Bar or dot display mode externally selectable by user Expandable to displays of 100 steps Internal voltage reference from 1.2V to 12V Operates with singlesupply of less than 3V Inputs operate down to ground Output current programmable from 2 mA to 30 mA No multiplex switching or interaction between outputs Input withstands ± 35V without damage or false outputs LED driver outputs are current regulated, open-collectors n Outputs can interface with TTL or CMOS logic n The internal 10-step divider is floating and can be referenced to a wide range ofvoltages n n n n n n n n n n

© 2004 National Semiconductor Corporation

DS007970

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LM3914

Typical Applications
0V to 5V Bar Graph Meter

00797001

Note: Grounding method is typical of all uses. The 2.2µF tantalum or 10 µF aluminum electrolytic capacitor is needed if leads to the LED supply are 6" or longer.

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LM3914

Absolute MaximumRatings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Power Dissipation (Note 6) Molded DIP (N) Supply Voltage Voltage on Output Drivers Input Signal Overvoltage (Note 4) Divider Voltage Reference Load Current 1365 mW 25V 25V

Storage Temperature Range Soldering Information...