Specification Sheet

Voltage − 2 V/div
Time − 0.1 ms/div
Capacitor Voltage
Output Voltage
Input Voltage
V
CC
= 5 V
R
A
= 1250 Ω
C = 0.02 µF
See Figure 9
f − Free-Running Frequency − Hz
C − Capacitance − µF
100 k
10 k
1 k
100
10
1
1001010.10.01
0.1
0.001
R
A
+ 2 R
B
= 10 MΩ
R
A
+ 2 R
B
= 1 MΩ
R
A
+ 2 R
B
= 100 kΩ
R
A
+ 2 R
B
= 10 kΩ
R
A
+ 2 R
B
= 1 kΩ
NA555 , NE555 , SA555 , SE555
SLFS022I –SEPTEMBER 1973–REVISED SEPTEMBER 2014 www.ti.com
Feature Description (continued)
Figure 14. Free-Running Frequency
8.3.3 Frequency Divider
By adjusting the length of the timing cycle, the basic circuit of Figure 9 can be made to operate as a frequency
divider. Figure 15 shows a divide-by-three circuit that makes use of the fact that re-triggering cannot occur during
the timing cycle.
Figure 15. Divide-by-Three Circuit Waveforms
8.4 Device Functional Modes
Table 1. Function Table
RESET TRIGGER VOLTAGE
(1)
THRESHOLD VOLTAGE
(1)
OUTPUT DISCHARGE SWITCH
Low Irrelevant Irrelevant Low On
High <1/3 V
CC
Irrelevant High Off
High >1/3 V
CC
>2/3 V
CC
Low On
High >1/3 V
CC
<2/3 V
CC
As previously established
(1) Voltage levels shown are nominal.
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