Periodic noise is one of the most common interference sources in the power distribution network of integrated circuits. It is well known that this noise can deleteriously affect timing margins and limit the circuit performance. This paper presents a theory on the response of ring oscillators in presence of periodic interference on the power supply. The theory links the cycle time of ring oscillators to the probability density function of the interference. Various waveforms of interference are studied, such as sinusoidal, triangular, and square. In addition, symmetrical and asymmetrical interference waveforms are also considered. Both transistor level HSPICE simulations and real measurements are performed to validate the theory. The obtained results are suitable with the model over a wide range of interference frequency. The valid range of the model, multi-tone interference, and methods to reduce the sensitivity of ring oscillators are also discussed.

周期性噪声是集成电路配电网络中最常见的干扰源之一。众所周知，这种噪声会有害地影响时序裕度并限制电路性能。本文提出了一种在电源受到周期性干扰的情况下环形振荡器响应的理论。该理论将环形振荡器的循环时间与干扰的概率密度函数联系起来。研究了各种干扰波形，例如正弦波，三角形和正方形。另外，还考虑了对称和非对称干扰波形。晶体管级HSPICE仿真和实际测量都可以验证该理论。所获得的结果适用于该模型在较大干扰频率范围内的情况。