Tags: ADC, education, LSB, least significant bit, theory


          For an ADC, a value of the LSB is calculated as follows:


LSB equation


where N is a number of bits. “Input voltage range” is the difference between maximum and minimum voltage values that ADC is able to convert. “Input voltage range” may be rail-to-rail and equal to VDD – VGND.


          Fig. 37 presents the transfer response of an ideal 3-bit ADC. Using the given definition of LSB, the LSB for the ADC is equal to:


LSB - 3-bit example


          Thus, one least significant bit LSB is equal to an analog value of 0.5 V:


1 LSB  =  0.5 V


LSB 3-bit plot

Figure 37: Transfer curve of an ideal 3-bit ADC, where power supply VDD is equal to 4V.