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PDF LM3914 Data sheet ( Hoja de datos )
| Número de pieza | LM3914 | |
| Descripción | Dot/Bar Display Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM3914 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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January 2000
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 mov-
ing 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 of the whole system from
less than 3V.
The circuit contains its own adjustable reference and accu-
rate 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 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 LM3914s
can be “chained” to form displays of 20 to over 100 seg-
ments. Both ends of the voltage divider are externally avail-
able 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 ex-
ternal 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 dis-
play is avoided. Various novel displays are possible.
Much of the display flexibility derives from the fact that all
outputs are individual, DC regulated currents. Various effects
can be achieved by modulating these currents. The indi-
vidual 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 program-
mer, 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.
The following typical application illustrates adjusting of the
reference to a desired value, and proper grounding for accu-
rate operation, and avoiding oscillations.
Features
n Drives LEDs, LCDs or vacuum fluorescents
n Bar or dot display mode externally selectable by user
n Expandable to displays of 100 steps
n Internal voltage reference from 1.2V to 12V
n Operates with single supply of less than 3V
n Inputs operate down to ground
n Output current programmable from 2 mA to 30 mA
n No multiplex switching or interaction between outputs
n Input withstands ±35V without damage or false outputs
n 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 of voltages
© 2000 National Semiconductor Corporation DS007970
www.national.com
1 page  
Typical Performance Characteristics (Continued)
Reference Adjust Pin
Current vs Temperature
LED Current-Regulation
Dropout
LED Driver Saturation
Voltage
Input Current Beyond
Signal Range (Pin 5)
DS007970-22
LED Current vs
Reference Loading
DS007970-23
LED Driver Current
Regulation
DS007970-24
Total Divider Resistance
vs Temperature
DS007970-25
DS007970-26
Common-Mode Limits
Output Characteristics
DS007970-27
DS007970-28
DS007970-29
5
DS007970-30
www.national.com
5 Page 
Typical Applications (Continued)
“Exclamation Point” Display
DS007970-9
LEDs light up as illustrated with the upper lit LED indicating the actual input voltage. The display appears to increase resolution and provides an analog
indication of overrange.
Indicator and Alarm, Full-Scale Changes Display from Dot to Bar
DS007970-10
*The input to the Dot-Bar Switch may be taken from cathodes of other LEDs. Display will change to bar as soon as the LED so selected begins to light.
11 www.national.com
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet LM3914.PDF ] | |
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