• LM3914 DOT/BAR DISPLAY DRIVER

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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 Single Supply of Less than 3V

  • Inputs Operate Down to Ground

  • Output Current Programmable from 2 mA to 30mA

  • 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


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 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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LM3914 DOT/BAR DISPLAY DRIVER

  • Product Code: LM3914 DOT/BAR DISPLAY DRIVER - BA22
  • Availability: 7
  • R50.00