Epson Insights

Why Measuring Power Supply Noise on Oscillators Matters

EpsonAugust 31, 2020

Jitter negatively influences the Bit-Error-Rate performance of digital communication systems. Sometimes expressed as phase noise, it’s a common specification applied to clocks and frequency sources and describes variable fluctuations in what should be a steady, unvarying signal. Component manufacturers generally measure phase noise under ideal conditions when developing product specifications. However, in real-world use cases, phase noise is often higher than what is published in the manufacturer’s specifications and rarely can be determined from component specifications alone.

When attempting to isolate these problems, common phase noise sources are the power supply and ground. These contributions are often not included in product specifications and vary widely between products. Without this information, it can be challenging to select the best performing oscillator from a product datasheet alone. By using the Power Supply Noise Rejection test outlined in this paper, you can account for phase noise when the specifications don’t.