Datasheet

LM3914
SNVS761B –JANUARY 2000–REVISED MARCH 2013 www.ti.com
*The exact wiring arrangement of this schematic shows the need for Mode Select (pin 9) to sense the V
+
voltage
exactly as it appears on pin 3.
Programs LEDs to 10mA
Figure 24. 20-Segment Meter with Mode Switch
APPLICATION HINTS
Three of the most commonly needed precautions for using the LM3914 are shown in the first typical application
drawing showing a 0V–5V bar graph meter. The most difficult problem occurs when large LED currents are being
drawn, especially in bar graph mode. These currents flowing out of the ground pin cause voltage drops in
external wiring, and thus errors and oscillations. Bringing the return wires from signal sources, reference ground
and bottom of the resistor string (as illustrated) to a single point very near pin 2 is the best solution.
Long wires from V
LED
to LED anode common can cause oscillations. Depending on the severity of the problem
0.05μF to 2.2μF decoupling capacitors from LED anode common to pin 2 will damp the circuit. If LED anode line
wiring is inaccessible, often similar decoupling from pin 1 to pin 2 will be sufficient.
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