PCB calculators / Power
Free tool · PreBuild Engineering
Buck and boost converter calculator
Size the inductor and capacitors for a buck or boost converter, and check peak currents against part ratings.
Inputs
V
Buck: use max Vin. Boost: use min Vin.
V
A
kHz
%
mV
%
Result
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Why it matters
Most converter failures on first prototypes come from inductors that saturate at peak current, output capacitors that lose most of their value at DC bias, and input capacitors that cannot handle the RMS current.
Formula
Buck (TI SLVA477): D = Vout/(Vin·η), L = Vout·(Vin − Vout) / (Vin·f·ΔI), ΔI = ripple % × Iout, Cout = ΔI / (8·f·ΔV)
Boost (TI SLVA372): D = 1 − Vin·η/Vout, L = Vin·(Vout − Vin) / (Vout·f·ΔI), ΔI = ripple % × Iout·Vout/(Vin·η), Cout = Iout·D / (f·ΔV)
Design tips
- Always check the controller datasheet's own equations and compensation requirements: they take precedence.
- Size Cout using effective capacitance at the output voltage (see the MLCC DC bias calculator).
- Keep the hot loop (input cap, switch, diode/sync FET) as small as possible.
Results are engineering estimates from standard formulas and published approximations. Always confirm against component datasheets, your fabricator's capabilities and, for critical designs, simulation or measurement.