Abstract:It is well known that continuous-time Delta-Sigma modulators are very sensitive to clock jitter effects. In literature, a number of techniques have been proposed to cope with them. In this brief, we present a detailed review and comparison of the reported techniques. While the effectiveness to reduce clock jitter effects may be of most importance in this comparison, we also consider other performance metrics such as circuit complexity and overhead to implement the technique, power consumption overhead of technique, synthesis complexity incurred in system-level design, extensibility of the technique from single-bit to multi-bit operation, and robustness to process variation. When clock jitter is relatively large, the fixed-width pulse feedback technique is most effective to reduce clock jitter effects among all techniques at high sampling frequency, while switched-capacitor-resistor and switched-shaped current techniques have best performance at medium frequency or below.

A recently proposed method to reduce clock jitter effects in continuous-time Delta-Sigma modulators is to generate a return-to-zero feedback with a fixed-width pulse for active feedback. In practice, the pulse width is subject to noise effects causing jitter of the pulse width itself. Therefore, jitter of the pulse width, though not the clock, may still degrade the performance of Delta-Sigma modulators. In this brief, we investigate practical feasibility of the method. It is shown that jitter of the pulse width could be conditionally much smaller than that of the clock, which therefore reduces clock jitter effects.

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