LM3914N-1 Datasheet, PDF (1/29 Pages) Texas Instruments – LM3914 Dot/Bar Display Driver

LM3914
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SNVS761B – JANUARY 2000 – REVISED MARCH 2013
LM3914 Dot/Bar Display Driver
Check for Samples: LM3914
FEATURES
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•2 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 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
• Outputs can Interface with TTL or CMOS Logic
• The Internal 10-step Divider is Floating and
can be Referenced to a Wide Range of
Voltages
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 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
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 held typically to
½%, 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 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 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.
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 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 PDIP
(NFK) package.
The following typical application illustrates adjusting
of the reference to a desired value, and proper
grounding for accurate operation, and avoiding
oscillations.
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2
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