LM3915N-1

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 displays. 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-

praetors 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.