A VCO Linearization Technique Using Dual-VCO and Interpolation for Time-Based ADCs

A VCO linearization technique for time-based ADCs increases the input range by interpolating the VCO's V-F transfer characteristic. Utilizing a dual-VCO and exploiting the intrinsic expansive and compressive regions of the transfer characteristic, the proposed technique reduces the nonlinearity after quantization in the digital domain. A detailed study reveals the optimal regions of operation and contrasts the linearity with that from the conventional single-VCO topology. Simulations show the proposed technique increases the input amplitude to 120% of the supply voltage and improves the ADC SNDR by 30.6 dB and SFDR by 32.7dB compared to the conventional design.