LM555J/883/NOPB National Semiconductor, LM555J/883/NOPB Datasheet - Page 6

• Manufacturer Part Number: LM555J/883/NOPB
• Manufacturer: National Semiconductor
• Type: Standardr

Specifications of LM555J/883/NOPB

• # Internal Timers: 1
• Power Dissipation: 1.18W
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (typ): 5/9/12/15V
• Operating Supply Voltage (max): 18V
• Package Type: CDIP
• High Level Output Current: -200mA
• Low Level Output Current: 200mA
• Pin Count: 8
• Operating Temp Range: -55C to 125C
• Operating Temperature Classification: Military
• Mounting: Through Hole
• Lead Free Status / RoHS Status: Compliant

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Applications Information
ASTABLE OPERATION
If the circuit is connected as shown in Figure 4 (pins 2 and 6
connected) it will trigger itself and free run as a multivibrator.
The external capacitor charges through R
charges through R
set by the ratio of these two resistors.
In this mode of operation, the capacitor charges and dis-
charges between 1/3 V
mode, the charge and discharge times, and therefore the fre-
quency are independent of the supply voltage.
Figure 5 shows the waveforms generated in this mode of
operation.
FIGURE 3. Time Delay
B
FIGURE 4. Astable
. Thus the duty cycle may be precisely
CC
and 2/3 V
CC
. As in the triggered
(Continued)
A
+ R
B
and dis-
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6
V
TIME = 20 µs/DIV.
R
R
C = 0.01 µF
The charge time (output high) is given by:
And the discharge time (output low) by:
Thus the total period is:
The frequency of oscillation is:
Figure 6 may be used for quick determination of these RC
values.
The duty cycle is:
FREQUENCY DIVIDER
The monostable circuit of Figure 1 can be used as a fre-
quency divider by adjusting the length of the timing cycle.
Figure 7 shows the waveforms generated in a divide by three
circuit.
CC
A
B
= 3.9 k
= 3 k
= 5V
FIGURE 6. Free Running Frequency
FIGURE 5. Astable Waveforms
T = t
t
Top Trace: Output 5V/Div.
Bottom Trace: Capacitor Voltage 1V/Div.
1
1
+ t
= 0.693 (R
t
2
2
= 0.693 (R
= 0.693 (R
A
+ R
B
) C
A
B
+2R
) C
B
) C
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