LM555C Harris Corporation, LM555C Datasheet - Page 4

• Manufacturer Part Number: LM555C
• Description: Timers for Timing Delays and Oscillator Application
• Manufacturer: Harris Corporation

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DataSheet
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NOTE: All resistance values are in ohms.
Since the charge rate and threshold level of the comparator
are both directly proportional to V+, the timing interval is rel-
atively independent of supply voltage variations. Typically,
the timing varies only 0.05% for a 1V change in V+.
Applying a negative pulse simultaneously to the reset termi-
nal (4) and the trigger terminal (2) during the timing cycle
discharges C
Momentarily closing only the reset switch during the timing
interval discharges C
Figure 2 shows the typical waveforms generated during this
mode of operation, and Figure 3 gives the family of time
delay curves with variations in R
VOLTAGE (TERMINALS 6, 7)
.com
FIGURE 1. RESET TIMER (MONOSTABLE OPERATION)
VOLTAGE (TERMINAL 2)
FIGURE 2. TYPICAL WAVEFORMS FOR RESET TIMER
(TERMINAL 3)
3.3V
CAPACITOR
R
VOLTAGE
3V
C
5V
OUTPUT
1
INPUT
T
0
0
0
SWITCH S
SWITCH S
T
RESET
START
4.7K
7
6
and causes the timing cycle to restart.
S
1
CA555
T
1
4
2
, but the timing cycle does not restart.
“CLOSED”
1
“OPEN”
1
8
5
EO
0.01 F
1
3
CA555, CA555C, LM555, LM555C, NE555
and C
t
D
680
10K
680
T
.
RELAY
COIL
1N4001
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5V
V+
8-6
Repeat Cycle Timer (Astable Operation)
Figure 4 shows the CA555 connected as a repeat cycle
timer. In this mode of operation, the total period is a function
of both R
the duty cycle is:
Typical waveforms generated during this mode of operation
are shown in Figure 5. Figure 6 gives the family of curves of
free running frequency with variations in the value of
(R
--------------- - =
t
FIGURE 3. TIME DELAY vs RESISTANCE AND CAPACITANCE
where t
1
FIGURE 4. REPEAT CYCLE TIMER (ASTABLE OPERATION)
t
+
1
0.001
1
and t
0.01
100
t
+ 2R
0.1
2
10
1
10
T = 0.693 (R
1
2
-5
----------------------- -
R
R
2
1
T
V+ = 5V
R
R
C
= 0.693 (R
= 0.693 (R
1
) and C
A
1
1
2
and R
T
+
+
= 25
2R
R
10
2
o
2
7
6
C
-4
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2.
T
R
.
1
1
1
2
CA555
4
2
= 1k
) C
+ 2R
+ R
10
1
T
-3
2
) C
TIME DELAY(s)
2
8
5
10k
) C
EO
0.01 F
T
T
10
3
100k
= t
-2
1
RELAY
COIL
+ t
1M
10
2
-1
10M
5V
1
V+
10