ADC Resolution
It shows into how many separate steps the analog reference voltage is divided when converted to digital; 8 bits means 256, 10 bits 1024 and 12 bits 4096 steps. On a 5 V scale, 10-bit resolution gives about 4.9 mV per step and 12-bit about 1.2 mV, and this determines how finely the speed can be set.
The driver's microcontroller cannot use the potentiometer or analog input voltage directly; it first converts it to a number. The more steps there are, the more stepless the speed reference feels.
- Practical limit: 10-bit resolution, with 1024 steps, provides a distribution in the speed setting finer than the human eye and ear can distinguish. That is why an expensive 12-bit converter is not needed in most applications.
- Noise floor: if there is 10 mV of interference on the board, the 1.2 mV steps of a 12-bit converter are meaningless; the last 3 bits keep moving. Before increasing resolution, the filtering must be fixed.
- Range used: if the pot uses only the 0–3 V band of the 5 V scale, you actually get about 614 steps rather than 1024.
When converting the raw reading into an output duty ratio, the driver is limited by its own PWM resolution; the ADC's 1024 steps come down to 256 in practice if the PWM is 8-bit.
Context where this term is used: DC Motor Driver Selection Guide