SA555 Fairchild Semiconductor, SA555 Datasheet - Page 7
SA555
Manufacturer Part Number
SA555
Description
Timers & Support Products
Manufacturer
Fairchild Semiconductor
Type
Standardr
Datasheet
1.SA555.pdf
(14 pages)
Specifications of SA555
Number Of Internal Timers
1
Supply Voltage (max)
16 V
Supply Voltage (min)
4.5 V
Maximum Power Dissipation
600 mW
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Mounting Style
Through Hole
Package / Case
PDIP-8
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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Company
Part Number
Manufacturer
Quantity
Price
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Manufacturer:
S
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Company:
Part Number:
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Manufacturer:
Texas Instruments
Quantity:
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Part Number:
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Manufacturer:
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Manufacturer:
S
Quantity:
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The equivalent circuit for discharging capacitor C1, when timer output is low is, as follows:
Since the duration of the timer output low state(
Since R
t
Consequently, if the timer operates in astable, the period is the same with
'T=t
time. And since frequency is the reciprocal of the period, the following applies.
3. Frequency divider
3. Frequency divider
3. Frequency divider
3. Frequency divider
By adjusting the length of the timing cycle, the basic circuit of Figure 1 can be made to operate as a frequency divider. Figure
8. illustrates a divide-by-three circuit that makes use of the fact that retriggering cannot occur during the timing cycle.
L
=0.693R
t
V
L
frequency,
H
V C1 t
t
C 1
C1
H
+t
=
C1
L
D
dv
--------------
=
C
=0.693(RA+R
t
dt
1
is normally R
C
C1
B
1
-- - V
3
=
1
R
C
=
V
1
CC
B
+
2
-- - V
3
R
2
-- - V
3
C1
---------------------- - V
R
+
A
(0-)=2Vcc/3
CC
CC
A
R
+
=
D
1
+
R
2
-- - V
3
R
e
f
=
R
B
B
-
In2
=
------------------------------------ -
B
B
CC
V
B
R A
In2
)C
CC
>>R
-- -
T
1
=
C1
+
e
1
=
R D
-
t
+0.693R
0.693 R
=
------------------------------------ -
1
D
R A
=
--------------------------------------- -
0.693 R
R
–
C1
0
although related to the size of discharging Tr.,
+
A
2
-- - e
3
t L
R D
+
1.44
-
B
2R
B
–
C1
------------------------------------
C
A
+
R A
B
6
1
7
R
+
=0.693(R
+
D
C
R
t H
R B
1
B
C
8
C1
1
C
t
L
1
R
) is the amount of time it takes for the V
D
A
11
+2R
9
5
B
4
)C
(10)
1
' because the period is the sum of the charge time and discharge
C1
(t) to reach Vcc/3,
LM555/NE555/SA555
7 7 7 7