The NTE1508 is a monolithic integrated circuit in an 18鈥揕ead DIP type package that senses analog
voltage levels and drives 10 LEDs, providing a linear analog display. A single pin changes the display
from a moving dot to a bar graph. Current drive to the LEDs is regulated and programmable, eliminating
the need for resistors. This feature is one that allows operation of the whole system from less than 3V.
The circuit contains its own adjustable reference and accurate 10鈥搒tep voltage divider. The low鈥?/div>
bias鈥揷urrent input buffer accepts signals down to GND, or V鈥? yet needs no protection against inputs
of 35V above or below GND. The buffer drives 10 individual comparators referenced to the precision
divider. Indication non鈥搇inearity can thus be held typically to 1/2%, even over a wide temperature
range.
Versatility was designed into the NTE1508 so that controller, visual alarm, and expanded scale functions
are easily added on to the display system. The circuit can drive LEDs of many color, or low鈥揷urrent
incandescent lamps. Many NTE1508s can be 鈥渃hained鈥?to form displays of 20 to over 100 segments.
Both ends of the voltage divider are externally available so that 2 drivers can be made into a zero鈥揷enter
meter.
The NTE1508 is very easy to apply as an analog meter circuit. A 1.2V full鈥搒cale meter requires only
1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1 resistor is a pot,
it becomes the LED brightness control
When in the dot mode, there is a small amount of overlap or 鈥渇ade鈥?(about 1mV) between segments.
This assures that at no time will all LEDs be 鈥淥FF鈥? and thus any ambiguous display is avoided. Vari-
ous novel displays are possible.
Much of the display flexibility derives from the fact that all outputs are individual, DC regulated cur-
rents. Various effects can be achieved by modulating these currents. The individual outputs can drive
a transistor as well as a LED at the same time, so controller functions including 鈥渟taging鈥?control can
be performed. The NTE1508 can also act as a programmer, or sequencer.
Features:
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Drives LEDs, LCDs or vacuum fluorescents
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Bar or dot display mode externally selectable
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by user
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Expandable to displays of 100 steps
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Internal voltage reference from 1.2V to 12V
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Operates with single supply of less than 3V
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Inputs operate down to GND
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Output current programmable from 2 to 30mA
No multiplex switching or interaction between
outputs
Input withstands
鹵35V
without damage or false
outputs
LED driver outputs are current regulated,
open鈥揷ollectors
Outputs can interfere with TTL or CMOS logic
The internal 10鈥搒tep divider is floating and can
be referenced to a wide range of voltages
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2
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