It's difficult to do any serious design or troubleshooting without an oscilloscope. But even with the best scopes, some problems are so elusive they defy solution. Intermittent problems are the worst. In some cases, it may be possible to sit and stare at the scope long enough to actually get a look at the glitch. But who has the time or patience to do that? Furthermore, some glitches are so subtle you may not recognize them without some serious examination.
Lecroy's solution to such problems, WaveScan, is built into the company's new WaveRunner Xi and WaveSurfer Xs scope models. While even the best scope trigger may not be able to find unusual events that are messing up your design or eluding a service tech or engineer, WaveScan lets users locate unusual events in a single capture or scan for an event in many acquisitions over a long period of time.
Designers can select from 20 special search modes such as pulse width, rise time, frequency, or duty cycle and apply a search condition like greater than, less than, within a range, outside a range, or a set value with limits. Next, the user starts the scan. WaveScan will then identify the event with a red box and list the values in a table. From there, users can zoom in to view or to apply additional analysis tools for further debugging.
The WaveRunner Xi and WaveSurfer Xs scopes are Lecroy's most popular models (Fig. 1). The new versions expand the bandwidth of each series, and the WaveScan feature is standard on both. The more powerful WaveRunner 104Xi includes four channels and 1-GHz bandwidth, and the Xi204 provides four channels with a bandwidth of 2 GHz. Both offer 5 Gsamples/s on four channels interleaved to 10 Gsamples/s.
The new WaveSurfer 104Xs brings the bandwidth of this series up to 1 GHz with a sample rate of 2.5 Gsamples/s on four channels interleaved to 5 Gsamples/s. Other WaveSurfer models have bandwidths of 400 and 600 MHz with either two or four channels. The 1-GHz model is only available with four channels.
WaveScan builds on Lecroy's strength in scope computing. A Lecroy scope can quickly calculate a measurement value for all instances of a measurement in an acquisition. As a result, hundreds or thousands of measurements can be made in a single acquisition and results returned in the same amount of time that other scopes require to deliver a single measurement value.
Lecroy uses that ability to go beyond just hardware triggering. In addition to being able to search for an unusual event in a single acquisition, WaveScan can search for an event over a period of hours or days and perform a number functions once the events are found.
Multiple scanning modes provide far more analysis power than a hardware trigger. If the mode is frequency, the scope will identify off-frequency conditions. It also will provide the option to continue scanning, save a screen image, or stop scanning.
Found events can be overlaid in a ScanOverlay view to provide a quick and simple comparison to one another. A ScanHistogram also can be created to show the statistical distribution of the found events. These analysis tools simplify the understanding of circuit operation and enable faster debugging.
The new WaveRunner Xi features a standard memory of 10 million sample points/channel. Mpts/Ch is a measure of how many data sampling points a digital scope is able to store on each input channel each time it is triggered. In effect, it's directly related to the amount of signal time that can be recorded at the scope's maximum sampling rate.
The 10 Mpts/Ch are interleaved to 20 Mpts/Ch. If a larger memory is needed, a 12.5-Mpt/Ch (interleaved to 25 Mpts/Ch) option is available. The WaveSurfer Xs scope also gets a new memory option. Its specification is 10 Mpts/Ch for two or four channels.
The new WaveRunner Xi and WaveSurfer Xs scopes have two new interface options, one for I2C, and one for a serial peripheral interface (SPI). Both of these interfaces are widely used in embedded design and test. These options let users look at the waveforms or decode the protocols and display them next to the data. Also, the scopes have search and zoom capability.
Best of all, these options give users wide latitude in selecting a trigger condition. Some scopes only allow an "equal" trigger condition, but these new options let users select other conditions, including data format. A controller-area network (CAN) interface option has been available for some time.
A high-frequency scope is only as good as its probes allow it to be. According to the company, Lecroy's latest high-impedance active probe better meets customer needs. Customers told Lecroy they wanted a 1-MΩ input impedance probe with a 1-pF capacitance max and a better grounding method—and Lecroy delivered.
The new XS models are single-ended active probes for 1 and 1.5 GHz (Fig. 2). The input capacitance is a low 0.9 pF. These probes also have a wide range of standard and optional probe tips and ground accessories for probing IC legs, surface-mount components, ball-grid arrays (BGAs), vias, square pins, and other tough probing challenges. And, these x10 attenuator probes have a dynamic range of ±8 V.
All of the new scopes and accessories are available, with delivery in four to eight weeks. The 104Xi costs $16,250, and the 204Xi costs $22,250. WaveSurfer for the 104Xs costs $12,890. Interface options cost $745 each. The XS1000 1-GHz probe costs $490, while the XS1500 1.5-GHz probe costs $1190.