LM3915N National Semiconductor, LM3915N Datasheet - Page 11

• Manufacturer Part Number: LM3915N
• Description: IC DRIVER DOT BAR DISPLAY 18-DIP
• Manufacturer: National Semiconductor

Specifications of LM3915N

• Display Type: LED, LCD, Vacuum Fluorescent
• Configuration: Dot/Bar Display
• Digits Or Characters: 10 Steps
• Current - Supply: 6.1mA
• Voltage - Supply: 3 V ~ 25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 18-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Other names: *LM3915N; LM3915

Application Hints
The scheme in Figure 10 is useful when the reference and
LED intensity must be adjusted independently over a wide
range The R
with no effect on LED current Since the internal divider here
does not load down the reference minimum LED current is
much lower At the minimum recommended reference load
of 80 A LED current is about 0 8 mA The resistor values
shown give a LED current range from 1 5 mA to 20 mA
At the low end of the intensity adjustment the voltage drop
across the 510
chip to chip variation in reference voltage may yield a visible
variation in LED intensity The optional approach shown of
connecting the bottom end of the intensity control pot to a
negative supply overcomes this problem by allowing a larger
voltage drop across the (larger) current-sharing resistors
Typical Applications
Optional circuit for improved intensity
matching at low currents See text
FIGURE 10 Wide-Range Adjustment of Reference Voltage and LED Intensity for Multiple LM3915s
FIGURE 9 Independent Adjustment of Reference Voltage and LED Intensity for Multiple LM3915s
HI
voltage can be adjusted from 1 2V to 10V
current-sharing resistors is so small that
(Continued)
11
Other Applications
For increased resolution it’s possible to obtain a display
with a smooth transition between LEDs This is accom-
plished by varying the reference level at pin 6 by 3 dBp-p as
shown in Figure 11 The signal can be a triangle sawtooth
or sine wave from 60 Hz to 1 kHz The display can be run in
either dot or bar mode
When an exponentially decaying RC discharge waveform is
applied to pin 5 the LM3915’s outputs will switch at equal
intervals This makes a simple timer or sequencer Each
time interval is equal to RC 3 The output may be used to
drive logic opto-couplers relays or PNP transistors for ex-
ample
TL H 5104 – 17
TL H 5104 – 18