Electrical retimer tackles challenges in designing chip-to-chip links

May 30, 2013 // By Graham Prophet
Agilent Technologies has introduced the latest addition to its repeater model library, in its Advanced Design System 2013, for quickly and accurately solving the challenge posed by signal distortion in the multigigabit-per-second regime.

Transient Convolution Element and SystemVue 2013 AMI Modelling Kit, is used for designing electrical retimers in chip-to-chip, high-speed digital links. Before the multigigabit era, chip-to-chip digital signals propagated across entire printed circuit boards with little distortion. However, at today’s speeds, rising and falling edges degrade after travelling only a few inches on production board materials such as FR4. In digital applications, it is cost-prohibitive to use high-frequency laminate board materials to solve the problem. A more economical solution is to insert a mid-channel retimer circuit.

Up to now, simulation tools used to design in these nonlinear devices have used computationally expensive SPICE techniques like Newton-Raphson iteration on modified nodal analysis of Kirchoff’s current law. With this latest breakthrough, Agilent offers a quick solution based on bit-by-bit channel simulation and the IBIS AMI flow to retimer applications. Unlike SPICE, these techniques include computationally efficient algorithms like superposition.

Using a prestandard, novel extension to the industry-standard IBIS AMI flow, SystemVue 2013 now offers model builders (typically integrated circuit vendors) a tool to build retimer models. The models run in ADS, the tool that IC consumers (typically data center and telecoms equipment manufacturers) use to design these chips into their systems.

“With our previous repeater model library release we added a simpler class of repeater models called redrivers,” said Colin Warwick, product manager for High-Speed Digital Design at Agilent EEsof EDA. “In general, retimers are more complex because they include additional circuitry for clock/data recovery. Our new retimer models join the existing redriver models to form a complete library of repeaters. We’re working with leading retimer and redriver IC vendors to make these models available to mutual customers.”

Agilent will submit a proposed enhancement to the IBIS Open Forum later this year. The intent is to incorporate the new techniques into a future version of the IBIS standard. This will ensure retimer model portability across EDA tools in future.

In addition, ADS 2013