CA555 View Datasheet(PDF) - Harris Semiconductor
Part Name
Description
View to exact match
CA555
Timers for Timing Delays and Oscillator Application in Commercial, Industrial and Military Equipment
Harris Semiconductor
CA555 Datasheet PDF : 6 Pages
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CA555, CA555C, LM555, LM555C, NE555
Electrical Specifications TA = 25oC, V+ = 5V to 15V Unless Otherwise Specified (Continued)
CA555, LM555 CA555C, LM555C, NE555
PARAMETER
SYMBOL TEST CONDITIONS
MIN TYP MAX MIN TYP MAX UNITS
Output Rise Time
tR
-
100
-
-
100
-
ns
Output Fall Time
tF
-
100
-
-
100
-
ns
NOTES:
2. When the output is in a high state, the DC supply current is typically 1mA less than the low state value.
3. The threshold current will determine the sum of the values of R1 and R2 to be used in Figure 4 (astable operation); the maximum total
R1 + R2 = 20MΩ.
Schematic Diagram
V+
THRESHOLD
COMPARATOR
8
4.7K 830
4.7K
D1
D2
Q3 Q4
THRESHOLD
6
Q1
Q7
Q2 Q5
CONTROL
VOLTAGE
5
2
TRIGGER
4
RESET
7
DISCHARGE
1
V-
10K
RESET
Q8
Q6
DISCHARGE
NOTE: Resistance values are in ohms.
TRIGGER
COMPARATOR
1K
5K
Q10
FLIP-FLOP
6.8K
Q16
7K
OUTPUT
Q19
3.9K
Q20
OUTPUT
3
5K
Q11 Q12
Q9
Q13
5K
100K
4.7K
D3
D4
Q15
Q14
Q18
220
Q17
Q21
4.7K
100
Typical Applications
Reset Timer (Monostable Operation)
Figure 1 shows the CA555 connected as a reset timer. In this
mode of operation capacitor CT is initially held discharged by
a transistor on the integrated circuit. Upon closing the “start”
switch, or applying a negative trigger pulse to terminal 2, the
integral timer flip-flop is “set” and releases the short circuit
across CT which drives the output voltage “high” (relay ener-
gized). The action allows the voltage across the capacitor to
increase exponentially with the constant t = R1CT. When the
voltage across the capacitor equals 2/3 V+, the comparator
resets the flip-flop which in turn discharges the capacitor rap-
idly and drives the output to its low state.
8-5
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