Datasheet

NE555, NE555Y, SA555, SE555, SE555C
PRECISION TIMERS
SLFS022A – SEPTEMBER 1973 – REVISED SEPTEMBER 2000
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
THRES
GND
C
R
A
R
L
V
CC
(5 V to 15 V)
Outpu
t
DISCH
OUT
V
CC
RESET
TRIG
CONT
Modulation
Input
(see Note A)
Clock
Input
NOTE A: The modulating signal can be direct or capacitively coupled
to CONT. For direct coupling, the effects of modulation
source voltage and impedance on the bias of the timer
should be considered.
48
3
7
6
2
5
Pin numbers shown are for the D, JG, and P packages.
1
Figure 18. Circuit for Pulse-Width Modulation
Voltage – 2 V/div
Time – 0.5 ms/div
Capacitor Voltage
Output Voltage
Clock Input Voltage
R
A
= 3 kΩ
C = 0.02 µF
R
L
= 1 kΩ
See Figure 18
Modulation Input Voltage
Figure 19. Pulse-Width Modulation Waveforms
pulse-position modulation
As shown in Figure 20, any of these timers can be used as a pulse-position modulator. This application
modulates the threshold voltage, and, thereby, the time delay, of a free-running oscillator. Figure 21 shows a
triangular-wave modulation signal for such a circuit; however, any wave shape could be used.
R
B
Modulation
Input
(see Note A)
CONT
TRIG
RESET V
CC
OUT
DISCH
V
CC
(5 V to 15 V)
R
L
R
A
C
GND
THRES
NOTE A: The modulating signal can be direct or capacitively coupled
to CONT. For direct coupling, the effects of modulation
source voltage and impedance on the bias of the timer
should be considered.
Pin numbers shown are for the D, JG, and P packages.
48
3
7
6
2
5
Output
Figure 20. Circuit for Pulse-Position Modulation
Figure 21. Pulse-Position-Modulation Waveforms
Voltage – 2 V/div
R
A
= 3 kΩ
R
B
= 500 Ω
R
L
= 1 kΩ
See Figure 20
Capacitor Voltage
Output Voltage
Modulation Input Voltage
Time – 0.1 ms/div