Flash ADC Utilizing Offset Voltage Variation With Order Statistics Based Comparator Selection

High-speed flash ADCs are required for wireless communication systems. However, the trade-off between area, power, and linearity suffers severely by offset voltage variation in sub-micron process. This paper proposes a flash ADC architecture that utilizes the offset voltage variation to reduce area and power consumption by eliminating reference generation. The proposed architecture utilizes offset voltages as references by selecting the appropriate comparators after an on-chip calibration. The on-chip calibration is performed based on order statistics that allows evaluating offset voltages in the time-domain. We verify our proposed architecture by HSPICE simulation based on a commercial 65 nm process. Our proposed architecture realizes a 5-bit ADC with the power consumption of less than 1 mW at 2 GS/s of operation, excluding the encoder.