LM3915 Datasheet, PDF (1/25 Pages) National Semiconductor (TI) – Dot/Bar Display Driver

February 2001
LM3915
Dot/Bar Display Driver
General Description
The LM3915 is a monolithic integrated circuit that senses
analog voltage levels and drives ten LEDs, LCDs or vacuum
fluorescent displays, providing a logarithmic 3 dB/step ana-
log display. One pin changes the display from a bar graph to
a moving dot display. LED current drive is regulated and
programmable, eliminating the need for current limiting re-
sistors. The whole display system can operate from a single
supply as low as 3V or as high as 25V.
The IC contains an adjustable voltage reference and an
accurate ten-step voltage divider. The high-impedance input
buffer accepts signals down to ground and up to within 1.5V
of the positive supply. Further, it needs no protection against
inputs of ±35V. The input buffer drives 10 individual com-
parators referenced to the precision divider. Accuracy is
typically better than 1 dB.
The LM3915’s 3 dB/step display is suited for signals with
wide dynamic range, such as audio level, power, light inten-
sity or vibration. Audio applications include average or peak
level indicators, power meters and RF signal strength
meters. Replacing conventional meters with an LED bar
graph results in a faster responding, more rugged display
with high visibility that retains the ease of interpretation of an
analog display.
The LM3915 is extremely easy to apply. A 1.2V full-scale
meter requires only one resistor in addition to the ten LEDs.
One more resistor programs the full-scale anywhere from
1.2V to 12V independent of supply voltage. LED brightness
is easily controlled with a single pot.
The LM3915 is very versatile. The outputs can drive LCDs,
vacuum fluorescents and incandescent bulbs as well as
LEDs of any color. Multiple devices can be cascaded for a
dot or bar mode display with a range of 60 or 90 dB.
LM3915s can also be cascaded with LM3914s for a linear/
log display or with LM3916s for an extended-range VU
meter.
Features
n 3 dB/step, 30 dB range
n Drives LEDs, LCDs, or vacuum fluorescents
n Bar or dot display mode externally selectable by user
n Expandable to displays of 90 dB
n Internal voltage reference from 1.2V to 12V
n Operates with single supply of 3V to 25V
n Inputs operate down to ground
n Output current programmable from 1 mA to 30 mA
n Input withstands ±35V without damage or false outputs
n Outputs are current regulated, open collectors
n Directly drives TTL or CMOS
n The internal 10-step divider is floating and can be
referenced to a wide range of voltages
The LM3915 is rated for operation from 0˚C to +70˚C. The
LM3915N-1 is available in an 18-lead molded DIP package.
© 2004 National Semiconductor Corporation DS005104
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