In this paper, we propose a dual-calibration technique to improve the matching accuracy of digital-to-analog converter (DAC) elements and improve nonlinearity induced static errors in a current-steering thermometer DAC. The novelty of the proposed dual-calibration scheme lies in obtaining best samples from the error distribution using redundancy for improved matching followed by adaptively reordering these samples to reduce error accumulation. This technique exploits the 2-D nature of the DAC to achieve lower calibration time. We consider the statistical basis for each of these methods and demonstrate statistical modeling of the proposed technique. We demonstrate a 38% reduction in differential nonlinearity (DNL) and 55% reduction in integral nonlinearity (INL) through simulations. We fabricated an 8-bit current steering thermometer DAC in Taiwan Semiconductor Manufacturing Company 65-nm CMOS process. With only 2 redundant cells per row, we show an improvement of 36% in DNL and 50% in INL from the measurement of 16 chips over the baseline DAC.

In this paper, a global clock network that incorporates standing waves and coupled oscillators to distribute a high-frequency clock signal with low skew and low jitter is described. The key design issues involved in generating standing waves on a chip are discussed, including minimizing wire loss within an available technology. A standing-wave oscillator, a distributed oscillator that sustains ideal standing waves on lossy wires, is introduced. A clock grid architecture comprised of coupled, standing-wave oscillators and differential, low-swing clock buffers is presented. The measured results for a prototyped standing-wave clock grid operating at 10GHz and fabricated in a 0.18μm 6M CMOS logic process are presented. A technique is proposed for on-chip skew measurements with sub-picosecond precision.