Agilent Jitter Analysis Using Keysight 2527s InfiniiVision 6000 X-Series and Infiniium Series - Application free download

File name Jitter Analysis Using Keysight_2527s InfiniiVision 6000 X-Series and Infiniium Series - Application

Keysight Technologies Jitter Analysis Using InfiniiVision 6000 X-Series and Infiniium Series Oscilloscopes Application Note Introduction As data rates continue to increase in today's state-of-the-art high-speed digital designs, timing budgets are decreasing. Ensuring that serial data signals are valid and stable when receivers sample the data often requires an understanding of the effects of the various components of jitter that may contribute to decreased valid data windows. The primary measurement tool used today by hardware design engineers to capture and view waveform jitter is an oscilloscope. Many of today's higher performance oscilloscopes also provide optional jitter analysis measurement capabilities that can not only be used to view jitter in different display formats, but they can also quantize the various components of jitter. This application note begins with a discussion of various display formats that can be used to view jitter, including horizontal waveform histograms, TIE histograms, TIE trend waveforms, and jitter spectrum waveforms. Also discussed are various clock recovery algorithms, real-time eye displays, jitter separation, and total jitter extrapolation. This application note wraps up with a comparison of how both the Keysight Technologies, Inc. 6000 X-Series and Infiniium Series oscilloscopes address these challenges. Composite views of jitter and clock recovery Let's begin by defining jitter. Jitter is the deviation of a timing event of a signal from its ideal position. This is often times referred to as Time Interval Error (TIE). Engineers often think of jitter as a "bouncing edge" relative to a reference (trigger point) as shown in Figure 1. In this measurement example, we are repetitively capturing an edge of a clock signal multiple cycles after a trigger reference edge on the same signal. One critical factor that enhances the scope's ability to quickly capture and display extremes of jitter such as this is fast waveform update rate. Also shown in Figure 1 is a waveform histogram plot of the jitter based on a narrow slice of waveform data around the 50% amplitude level. A horizontal waveform histogram plot displays the probability distribution function (PDF) of the composite jitter time-correlated to the captured waveforms. In this example we can see that the jitter has a bi-modal distribution. Waveform histogram measurements, which are the simplest type of jitter measurements and are one of the key measurement capabilities found in most of today's higher performance scopes, including Keysight's InfiniiVision 6000 X-Series and Infiniium Series oscilloscopes. Although capturing and viewing jitter on a repetitive clock signal is relatively straight forward, capturing and viewing jitter on a serial data signal is a bit more complex, especially if an explicit clock signal for triggering on is not available. Most