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|Power Dissipation:||1365 MW||Supply Voltage:||25V|
|Voltage On Output Drivers:||25V||Input Signal Overvoltage (Note 4):||±35V|
|Divider Voltage:||−100 MV To V+|
►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
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.
Absolute Maximum Ratings
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Power Dissipation (Note 6)
Molded DIP (N) 1365 mW
Supply Voltage 25V
Voltage on Output Drivers 25V
Input Signal Overvoltage (Note 4) ±35V
Divider Voltage −100 mV to V+
Reference Load Current 10 mA
Storage Temperature Range −55˚C to +150˚C
Soldering Information Dual-In-Line Package Soldering (10 seconds) 260˚C
Plastic Chip Carrier Package Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C