ts555 STMicroelectronics, ts555 Datasheet - Page 9

• Manufacturer Part Number: ts555
• Description: Low Power Single Cmos Timers
• Manufacturer: STMicroelectronics

ASTABLE OPERATION
When the circuit is connected as shown in figure 4
(pin 2 and 6 connected) it triggers itself and free
runs as a multivibrator. The external capacitor
charges through R
through R
cisely set by the ratio of these two resistors.
In the astable mode of operation, C charges and
discharges between 1/3 V
the triggered mode, the charge and discharge
times and therefore frequency, are independent of
the supply voltage.
Figure 4:
Voltage
0.01 F
Control
V
CC
Out
B
only. Thus the duty cycle may be pre-
5
Reset
3
A
1
4
TS555
and R
CC
8
and 2/3 V
B
2
and discharges
7
6
CC
R
R
. As in
C
B
A
Figure 5 shows actual waveforms generated in
this mode of operation.
The charge time (output HIGH) is given by :
t1 = 0.693 (R
and the discharge time (output LOW) by :
t2 = 0.693 x R
Thus the total period T is given by :
T = t1 + t2 = 0.693 (R
The frequency of oscillation is then :
The duty cycle is given by :
Figure 5:
D =
f =
-- - =
T
1
---------------------------
R A
RB
------------------------------------- -
( RA
+
R = R = 4.8 k , C = 0.1 F , R = 1.0k
2 RB
A
t = 0.5 ms / div
OUTPUT VOLTAGE = 5.0V/div
CAPACITOR VOLTAGE = 1.0V/div
A
+
1.44
B
+ R
B
2 R B C
x C
B
) C
A
+ 2R
B
) C
L
TS555
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