LMC555
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SNAS558J –FEBRUARY 2000–REVISED MARCH 2013
Figure 7. Time Delay
ASTABLE OPERATION
If the circuit is connected as shown in Figure 8 (Trigger and Threshold terminals connected together) it will
trigger itself and free run as a multivibrator. The external capacitor charges through RA + RB and discharges
through RB. Thus the duty cycle may be precisely set by the ratio of these two resistors.
Figure 8. Astable (Variable Duty Cycle Oscillator)
In this mode of operation, the capacitor charges and discharges between 1/3 VS and 2/3 VS. As in the triggered
mode, the charge and discharge times, and therefore the frequency are independent of the supply voltage.
Figure 9 shows the waveform generated in this mode of operation.
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