LM3915 Dot/Bar Display Driver
Features
♦ 3 dB/step, 30 dB range
♦ Drives LEDs, LCDs, or vacuum fluorescents
♦ Bar or dot display mode externally selectable by user
♦ Expandable to displays of 90 dB
♦ Internal voltage reference from 1.2V to 12V
♦ Operates with single supply of 3V to 25V
♦ Inputs operate down to ground
♦ Output current programmable from 1 mA to 30 mA
♦ Input withstands ±35V without damage or false outputs
♦ Outputs are current regulated, open collectors
♦ Directly drives TTL or CMOS
♦ The internal 10-step divider is floating and can be referenced to
a wide range of voltages
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 analog 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 resistors. 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 comparators 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 intensity or
vibration. Audio applications include average or peak level
indicators, power meters and RF signal streCM GROUPh 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.
Typical Applications
