555 IC Formulas

## Astable waveforms

Charge time (output high)

t1 = 0.693(Ra+Rb)C

Discharge time (output low)

t2 = 0.693(Rb)C

Total period

T = t1+t2 = 0.693(Ra+2Rb)C

Frequency of oscillation

f = 1/T = 1.44/(Ra+2Rb)C

Duty cycle

D = Rb/Ra+2Rb

## Monostable

Timeout Delay in secs

t3 = 1.1 * R1 * C1