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
The XD3915 is Rated for Operation from 0°C to
+70°C.

DESCRIPTION
The XD3915 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 XD3915 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 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 XD3915 is extremely easy to apply. A 1.2V fullscale
meter requires only one resistor in addition to
the ten LEDs. One more resistor programs the fullscale
anywhere from 1.2V to 12V independent of
supply voltage. LED brightness is easily controlled
with a single pot.
The XD3915 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. XD3915 can also be cascaded with
XD3914 for a linear/log display or with XD3916 for
an extended-range VU meter.