Specification Sheet

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, P, PS, and PW packages.
4 8
3
7
6
2
5
Output
NA555 , NE555 , SA555 , SE555
SLFS022I –SEPTEMBER 1973–REVISED SEPTEMBER 2014 www.ti.com
Typical Applications (continued)
Figure 20. Circuit for Pulse-Position Modulation
9.2.3.1 Design Requirements
Both DC and AC coupled modulation input will change the upper and lower voltage thresholds for the timing
capacitor. Both frequency and duty cycle will vary with the modulation voltage.
9.2.3.2 Detailed Design Procedure
The nominal output frequency and duty cycle can be determined using formulas in A-stable Operation section. R
L
improves V
OH
, but it is not required for TTL compatibility.
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