ADC Scaling

Turn raw ADC counts into engineering voltage with firmware constants.

Formulas

k = R2 / (R1 + R2); D = 2ᴺ or 2ᴺ − 1

Vpin = raw × Vref / D

Vmeasured = (Vpin − Voffset) / (k × G)

Input volts per count = Vref / (D × k × G)

Maximum reconstructed input = [(2ᴺ − 1) × Vref / D − Voffset] / (k × G)

Model & assumptions

Signal chain: input → divider → amplifier → offset → ADC. Maximum measurable input is defined here as the value reconstructed at the highest code.

The full-scale pin boundary maps to (Vref − offset) / (k × G). ADC transition locations, noise, INL, and device-specific coding are excluded.

Example with default inputs

Reconstructed measured voltage

9.15 V

ADC pin voltage

1.65 V

Input voltage per count

4.46777 mV

Maximum measurable input

18.2955 V

Minimum measurable input

0 V

Nominal full-scale boundary

18.3 V