A balanced rail-to-rail all digital comparator using only standard cells

An all-digital comparator with full input range is presented. It outperforms the nowaday all-digital comparators with its large rail-torail input range. This is achieved by the proposed “Yin-yang” balance mechanism between the two logic gates: NAND3 and OAI (Or-AndInvert). The important design considerations to achieve this balance are presented, such as the driving strength manipulation and the use of predistortion technique. Constructed only by commercially available digital standard cells, the layout of the proposed comparator is generated automatically by standard digital Place & Route routine within several minutes. The Verilog code for the proposed circuit is given, and the circuit is successfully implemented in 130nm CMOS technology with the power consumption of 0.176mW at the clock of 330MHz.