Specification Sheet

Voltage − 2 V/div
Time − 0.1 ms/div
Capacitor Voltage
Output Voltage
Input Voltage
R
A
= 9.1 kΩ
C
L
= 0.01 µF
R
L
= 1 kΩ
See Figure 9
− Output Pulse Duration − s
C − Capacitance − µF
10
1
10
−1
10
−2
10
−3
10
−4
1001010.10.01
10
−5
0.001
t
w
R
A
= 10 MΩ
R
A
= 10 kΩ
R
A
= 1 kΩ
R
A
= 100 kΩ
R
A
= 1 MΩ
V
CC
(5 V to 15 V)
R
A
R
L
Output
GND
OUT
V
CC
CONT
RESET
DISCH
THRES
TRIGInput
5
8
4
7
6
2
3
1
Pin numbers shown are for the D, JG, P, PS, and PW packages.
NA555 , NE555 , SA555 , SE555
SLFS022I –SEPTEMBER 1973–REVISED SEPTEMBER 2014 www.ti.com
Feature Description (continued)
Figure 9. Circuit for Monostable Operation
Monostable operation is initiated when TRIG voltage falls below the trigger threshold. Once initiated, the
sequence ends only if TRIG is high for at least 10 µs before the end of the timing interval. When the trigger is
grounded, the comparator storage time can be as long as 10 µs, which limits the minimum monostable pulse
width to 10 µs. Because of the threshold level and saturation voltage of Q1, the output pulse duration is
approximately t
w
= 1.1R
A
C. Figure 11 is a plot of the time constant for various values of R
A
and C. The threshold
levels and charge rates both are directly proportional to the supply voltage, V
CC
. The timing interval is, therefore,
independent of the supply voltage, so long as the supply voltage is constant during the time interval.
Applying a negative-going trigger pulse simultaneously to RESET and TRIG during the timing interval discharges
C and reinitiates the cycle, commencing on the positive edge of the reset pulse. The output is held low as long
as the reset pulse is low. To prevent false triggering, when RESET is not used, it should be connected to V
CC
.
Figure 10. Typical Monostable Waveforms Figure 11. Output Pulse Duration vs Capacitance
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