Generate pwm using ic 555

Introduction

IC 555

IC 555 is an astable multivibrator (oscillator).

Frequency: The ON time is defined by the time taken to its capacitor to charge to 1/e level through pin7 resistor, and the OFF time is the discharging time of the capacitor through pin7.

Method 1

${\begin{aligned}T_{\text{on}}&=0.693(R_{1}+R_{2})C\\T_{\text{off}}&=0.693R_{2}C\\f&={\frac {1.44}{(R_{1}+2R_{2})C}}\end{aligned}}$

555 internal design and theory

See https://www.electronicshub.org/555-timer-pwm/

and the internal circuit looks like below:

References

https://www.homemade-circuits.com/how-to-use-ic-555-for-generating-pwm/

https://www.electronicshub.org/555-timer-pwm/