Description:
The NTE1549 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs, or vacuum fluorescent displays, providing an electronic version of the popular VU meter. 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 3V or as high as 25V.
This 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 0.2dB.
Audio applications include average or peak level indicators, and power 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 NTE1549 is extremely easy to apply. A 12V full–scale meter requires only one resistor in addition to the ten LEDs. One more resistor program in addition to the full–scale anywhere from 1.2V to 12V independent of supply voltage. LED brightness is easily controlled with a single pot.
The NTE1549 is very versatile. The outputs can drive LCDs, vacuum fluorescents and incandescent bulb as well as LEDs of any color. Multiple devices can be cascaded for a dot or bar mode display for increased range and/or resolution.

FEATUREs:
• Fast responding electronic VU meter
• Drives LEDs, LCDs, or vacuum fluorescents
• Bar or dot display mode externally selectable by user
• Expandable to displays of 70dB
• Internal voltage reference from 1.2V to 12V
• Operates with a single supply of 3V to 25V
• Inputs operate down to ground
• Output current programmable from 1mA to 30mA
• Input withstands ±35V without damabe 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.