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.