NE555N/NE555D
Since RD is normally RB>>RD although related to the size of discharging Tr.,
Consequently, if the timer operates in astable, the period is the same with
'T=tH+tL=0.693(RA+RB)C1+0.693RBC1=0.693(RA+2RB)C1' because the period is the sum of
the charge time and discharge time. And since frequency is the reciprocal of the period, the
following applies.
3、 Frequency divider
By adjusting the length of the timing cycle, the basic circuit of Figure 1 can be made to
operate as a frequency divider. Figure8. illustrates a divide-by-three circuit that makes use
of the fact that retriggering cannot occur during the timing cycle.
4、 Pulse Width Modulation
The timer output waveform may be changed by modulating the control voltage applied
to the timer's pin 5 and changing the reference of the timer's internal comparators. Figure 9
modulation circuit. illustrates the pulse width
When the continuous trigger pulse train is applied in the monostable mode, the timer
output width is modulated according to the signal applied to the control terminal. Sine wave
as well as other waveforms may be applied as a signal to the control terminal. Figure 10
shows the example of pulse width modulation waveform.
8/11
TGS [ Tiger Electronic Co.,Ltd ]
