Switching Frequency Calculator — InnovChip

Switching Frequency Calculator

Convert between switching frequency and period, and dimension a 555-style astable oscillator from R1, R2 and C for PWM/clock generation.

Calculator

About This Calculator

Frequency and period are reciprocal; this tool converts either direction, then goes further to dimension a classic 555 astable multivibrator. In the astable configuration the charge path is R1+R2, the discharge path is R2, and the timing constant is ln(2) ≈ 0.693 per RC segment. The 555 can drive simple PWM or clock generation for switching regulators and logic.

How to Use

  1. Enter the switching frequency to see its period in µs (or reverse by computing f = 1/T).
  2. Enter R1, R2 and C of your 555 astable.
  3. Read the frequency, on/off times and duty cycle.
  4. Note the 555 duty is always > 50% (charge includes R1); use a comparator/buffer stage for outputs near 50%.

Formulas

Period ↔ frequencyT = 1 / f (µs = 1000 / f(kHz))
555 frequencyf = 1.44 / ((R1 + 2·R2) × C)
Timing constantt(on) = 0.693(R1+R2)C, t(off) = 0.693·R2·C

Design Notes

Units: R in kΩ and C in nF as entered — the constant 1.44 already accounts for the scale.

For high-stability clocking prefer a crystal/PLL; the 555 frequency drifts with supply and temperature.