Stochastic Subranging ADC Using Variable Comparator Offset Technique

We propose a stochastic subranging analog-to-digital converter using a variable comparator offset technique. The variable comparator offset technique enables the same comparator group to be utilized in both coarse and fine conversion phases; therefore, high resolution can be obtained with a small number of comparators. The offset current injector is added to the comparator, resulting in a variable offset. Moreover, variable offset averaging is also introduced. These techniques can change the standard deviation of the comparator group from 130 to 5 mV. The simulation results show that an average effective number of bits of 10 can be obtained when 255 × 9 comparators are used.