Dot/Bar Display Driver
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 the LEDs is regulated
and programmable, eliminating the need for resistors. This
feature is one that allows operation ofthe 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
buffer drives 10 individual comparators referenced to the
precision divider. Indication non-linearity can thus be heldtypically 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 LM3914s
can be “chained” to form displays of 20 to over 100 segments. Both ends of the voltage divider areexternally 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 LED brightness 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.
© 2000 National Semiconductor Corporation
Much of the display flexibility derives from the fact that all
outputs are individual, DC regulatedcurrents. 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 an 18-lead molded (N) package.
Thefollowing typical application illustrates adjusting of the
reference to a desired value, and proper grounding for accurate operation, and avoiding oscillations.
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 single supply of less than 3VInputs 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,
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 of voltages
LM3914 Dot/Bar Display Driver
0V to 5V Bar Graph Meter
Note: Grounding method is typical of all uses. The 2.2 µF tantalum or 10 µF aluminum electrolytic capacitor is needed if leads to the LED supply are 6" or
Reference Load Current
−55˚C to +150˚C
Soldering (10 seconds)
Plastic Chip Carrier Package
Vapor Phase (60 seconds)
Infrared (15 seconds)
See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.
If Military/Aerospace specified devices are required,...
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