LMC555

SNAS558J – FEBRUARY 2000 – REVISED MARCH 2013

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Top Trace: Output 5 V/Div.

TIME = 20 µs/Div.

Bottom Trace: Capacitor Voltage 1 V/Div.

C = 0.01 µF

Figure 9. Astable Waveforms

The charge time (output high) is given by

(1)

And the discharge time (output low) by:

(2)

Thus the total period is:

(3)

The frequency of oscillation is:

(4)

Figure 10 may be used for quick determination of these RC Values. The duty cycle, as a fraction of total period

that the output is low, is:

(5)

Figure 10. Free Running Frequency

8

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