As a developer of cutting edge integrated circuits (ICs), precision is absolutely essential. This includes the performance of the devices and the precise measurement of their performance. Being able to design and produce devices with jitter less than picoseconds is all very well, but if that cannot be accurately measured by the chip maker and by the customer, then there is a problem.

ON Semiconductor develops high performance ICs for high speed systems, particularly in telecommunications, and so is very aware of these requirements. Precise performance and measurement is particularly critical to the company's High Performance Analogue Business Unit, which develops Emitter-Coupled Logic (ECL) devices that are used to manage clock and data streams in electronic communications systems, networking products, and in automated test equipment.
Developing and testing ECL devices can be extremely challenging since they operate at very high speeds in the 3Gbit/s to 12Gbit/s range. ON Semiconductor has to support both clock and data signals in the same device meaning it must be able to acquire and measure the different types of jitter these signals produce. In addition, signal shifts in the realm of picoseconds (ps RMS) and femtoseconds (fs RMS) can disrupt TX/RX performance and cause critical issues when precision is the name of the game.
A similar challenge exists for ON Semiconductor's customers. With jitter being of utmost concern, precise jitter measurements and specifications are paramount.
ON Semiconductor's customers integrate components into more complete assemblies and products. They have the difficult task of meeting tight jitter budgets -- the total jitter is the sum of the individual jitter characteristics of each component -- to comply with stringent serial data standards such as Fibre Channel and SONET. As a result, the ICs that go into their products must produce the least possible jitter while delivering signal shifts that are lightning fast and unvarying over billions of cycles.
Therein lays the challenge for ON Semiconductor in the development of ECL devices: maintaining performance and lowering the specified jitter to reduce the burden on its customers' jitter budgets. Previously, ON Semiconductor could only measure its ECL devices down to a maximum jitter of 1psRMS. Test equipment that could practically and accurately measure below this limit simply did not exist.
"We knew our components were performing better and producing less than 1psRMS jitter, but we had no way of measuring it," said Bill Schromm, Vice President of ON Semiconductor's High Performance Analogue Business Unit. "That inability to quantify the true performance of our devices not only inhibited our capacity to validate and promote our competitive advantage, it also affected our customers who are working with extremely tight jitter budgets."
So ON Semiconductor used the Tektronix TDS8200 modular sampling oscilloscope. With configurations that provide bandwidth to 70GHz and both single-ended and differential clock recovery systems to cover all current and emerging serial data standards between 50Mbit/s and 12.6Gbit/s, the TDS8200 offers the a noise floor of 400uV with certain modules. Because of the TDS8200, ON Semiconductor can now test its ECL device jitter down below 200fs RMS, which is an improvement of five times over its previous measurement capabilities.
"As the speed of our designs increases, the eye closure associated with the 1psRMS system jitter of instruments currently in the market is becoming a significant issue," said William George, ON Semiconductor's Senior
Vice-President of Operations and Chief Manufacturing Officer. "The TDS8200 with the 82A04 phase reference module is the only measurement system that provides us with less than 200fsRMS system jitter and adequate bandwidth to characterise our new 6Gbit/s designs."
Designs with limited jitter budgets and tight timing margins require test equipment with the best signal fidelity and the ability to provide accurate and repeatable results. To handle differential signals, test equipment must be flexible enough to provide true differential acquisition and clock recovery across multiple data rates.
Using a customer supplied clock synchronous to the signal under the test, the 82A04 module can either e-jitter traditionally acquired samples, or dispense with the traditional trigger + timebase sample placing altogether and acquire in a free-run (random) mode. A key point is that the instrument can accept signal modules, clock recovery module, and a Phase Reference module all at the same time, so the clock recovery Clock Out signal can be used by the Phase Reference module to decrease the jitter of the acquired signal.
Using the TDS8200 eliminates false test failures and enables more accurate characterisation of design tolerances for increased component performance and reduced costs. Also, with the ability to trigger on embedded clocks and measure random and deterministic jitter, ON Semiconductor engineers are better able to perform accurate, repeatable compliance testing of igh-speed, low power differential signals.
Since ON Semiconductor can now measure and demonstrate the higher performance of its ECL devices, the company has been able to enhance their competitive advantage in the industry, streamline its own development processes and help its customers produce higher performance systems with lower design margins.
"The test process for ECL devices has been expedited and simplified using the TDS8200. In the past, we used two instruments and two set-ups to measure the different types of jitter produced by clock and data signals, and the results were imprecise. Now we have a single process with one powerful instrument," said Schromm.
The available electrical modules include a variety of modules with bandwidths up to 70GHz and specialised features such as Time Domain Reflectometry (TDR). For the TDR probing, the P8018 probe supports full TDR bandwidth, while the 80A02 module provides protection from the damage by electrostatic discharge. These features enable even measurements performed in manufacturing environment to achieve highly precise results, while protecting the TDR module itself.
An electrical clock recovery module covering most popular rates between 50Mbit/s and 12.6Gbit/s is available, and optical modules provide complete optical test solutions for both telecom (155Mbit/s to 43Gbit/s) and Datacom (Fibre Channel, InfiniBand and Gigabit Ethernet) applications, with clock recovery available as an option for most optical modules.

Hans-Peter Fleischheuer is European Marketing Manager for Oscilloscopes at Tektronix, Cologne, Germany www.tektronix.com