PRECISION TIMERS
SLFS022F – SEPTEMBER 1973 – REVISED JUNE 2006
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APPLICATION INFORMATION (continued)
Pulse-Position Modulation
As shown in
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.
shows a
triangular-wave modulation signal for such a circuit; however, any wave shape could be used.
V
CC
(5 V to 15 V)
4
RESET
2
TRIG
8
V
CC
OUT
R
L
3
R
A
Output
Voltage − 2 V/div
DISCH
Modulation
Input 5
(see Note A)
CONT
GND
THRES
7
R
B
6
C
Pin numbers shown are for the D, JG, P, PS, and PW packages.
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.
Figure 20. Circuit for Pulse-Position Modulation
14
ÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎÎÎÎÎÎ
ÎÎ
ÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
R
A
= 3 kΩ
R
B
= 500 Ω
R
L
= 1 kΩ
See Figure 20
Modulation Input Voltage
Output Voltage
Capacitor Voltage
Time − 0.1 ms/div
Figure 21. Pulse-Position-Modulation Waveforms
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