LM3914 Dot/Bar Display Driver
1FEATURES Versatility was designed into the LM3914 so that
controller, visual alarm, and expanded scale functions
2• Drives LEDs, LCDs or Vacuum Fluorescents are easily added on to the display system. The circuit
• Bar or Dot Display Mode Externally Selectable can drive LEDs of many colors, or low-current
by User incandescent lamps. Many LM3914s can be
“chained” to form displays of 20 to over 100 • Expandable to Displays of 100 Steps
segments. Both ends of the voltage divider are
• Internal Voltage Reference from 1.2V to 12V externally available so that 2 drivers can be made
• Operates with Single Supply of Less than 3V into a zero-center meter.
• Inputs Operate Down to Ground The LM3914 is very easy to apply as an analog
• Output Current Programmable from 2 mA to 30 meter circuit. A 1.2V full-scale meter requires only 1
mA resistor and a single 3V to 15V supply in addition to
the 10 display LEDs. If the 1 resistor is a pot, it • No Multiplex Switching or Interaction Between becomes the LED brightness control. The simplified Outputs block diagram illustrates this extremely simple
• Input Withstands ±35V without Damage or external circuitry.
When in the dot mode, there is a small amount of
• LED Driver Outputs are Current Regulated, overlap or “fade” (about 1 mV) between segments.
Open-collectors This assures that at no time will all LEDs be “OFF”,
• Outputs can Interface with TTL or CMOS Logic and thus any ambiguous display is avoided. Various
novel displays are possible. • The Internal 10-step Divider is Floating and
can be Referenced to a Wide Range of Much of the display flexibility derives from the fact
Voltages that all outputs are individual, DC regulated currents.
Various effects can be achieved by modulating these
DESCRIPTION currents. The individual outputs can drive a transistor
as well as a LED at the same time, so controller The LM3914 is a monolithic integrated circuit that functions including “staging” control can be senses analog voltage levels and drives 10 LEDs, performed. The LM3914 can also act as a providing a linear analog display. A single pin
programmer, or sequencer. changes the display from a moving dot to a bar
graph. Current drive to the LEDs is regulated and The LM3914 is rated for operation from 0°C to +70°C.
programmable, eliminating the need for resistors. The LM3914N-1 is available in an 18-lead PDIP
This feature is one that allows operation of the whole (NFK) package.
system from less than 3V.
The following typical application illustrates adjusting
The circuit contains its own adjustable reference and of the reference to a desired value, and proper
accurate 10-step voltage divider. The low-bias-current grounding for accurate operation, and avoiding
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
½%, even over a wide temperature range.
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