HTCSEMI HT3915ANZ

The HT3915 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 display. LED current drive is regulated and pro-grammable, eliminating the need for current limiting resis-tors. 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 ac-curate 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-parators referenced to the precision divider. Accuracy is typically better than 1 dB. The HT3915’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 HT3915 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 HT3915 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. HT3915s can also be cascaded with LM3914s for a linear/ log display or with LM3916s for an extended-range VU meter.

• 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

• Audio average or peak level indicator
• Power meter
• RF signal strength meter