Vstep = Vref/2^n

where n is the number of bits in the digital word.

Eg.

Vref = 5V

n = 8-bits

5V/256 = 19.5mV

41(decimal) x 19.5mV = 800mV.

Is it OK to use this same procedure for ADC successive approximation circuit calculations?

Eg.

Vsig = 3.6V

8-bit, 5V ADC

5V/256 = 19.5mV

Vsig/19.5mV = 183(decimal)