1.5.2 Unsigned Mode

In unsigned mode the conversion result from the ADC is:

R E S = V I N P + Δ V V R E F × T O P

VINP is the single ended input and ΔV = VREF x 0.05. TOP is the top value given by the configured resolution. For 12-bit mode TOP is 4096 and 8-bit mode TOP is 256.

The positive offset given by ΔV is typically 0.05*VREF. This typically corresponds to a measurement result of approximately 200 when the input pin is connected to ground. In order to measure this offset accurately the ADC should be configured as it will be used in the application (i.e. voltages, speed, and other settings) and the input pin should be connected externally to ground.

This offset is not automatically compensated, and the software needs to subtract the measured offset from the conversion results.

With 12-bit resolution the range from GND to VREF – ΔV will be from approximately 200 to 4095 (0x00C8 - 0x0FFF).