Get rid of the noise, keynoter advises

Get rid of the noise, keynoter advises
BOXBOROUGH, Mass. — Signal integrity has become designers' No. 1 hurdle as chips, boards and systems approach transfer rates of 10 Gbits/second, keynoter Henri Merkelo told the PCB East conference here Wednesday (Oct. 16). Designers have got to turn down that noise, and need algorithms that "simulate everything from circuits to connectors to solder bumps," said Merkelo, chief executive officer at atSpeed Technologies Corp. (Harrisburg, Pa.).

"At the gigabit transfer rates you need to design out what was originally designed in," said Merkelo. Anomalies that could be ignored at lower operating frequencies, and compensated for later in the design, must be attacked up front when designing circuits that operate at 10 Gbits/s, he said.

In his keynote address Merkelo showed examples of what simulations of passive and active compensation circuits can do in the early phases of design. As printed-circuit board traces increased from 6-mil to 10-mil thickness and trace lengths went from 600 mm to 1 meter, the typical "open-eye" waveforms appeared without a hitch. Merkelo tried this kind of simulation at various frequencies up to 12.4 Gbits/s — an especially sensitive frequency for compensating electromagnetic properties of circuit components. He emphasized that circuits being simulated and compensated were real circuits, and said he has worked with developers at Agilent Technologies, Meritec and Erni Components.

"Ten years ago I wrote a paper on noise compensation where I claimed that noise is not noise, and there are no parasitics," said Merkelo. His notion is that all the noise generated by circuits is originally designed into them inadvertently. If designers paid more attention to that phenomenon in the first place, they would not have to spend sleepless nights designing out crosstalk and other noise after the fact, he argued. Because this is especially true at high frequencies, simulations that can expose the proper compensation circuitry before the circuit is built would ensure better results.

Merkelo said that at these high frequencies, the technologies being applied to ICs, boards, connectors and even systems are merging and the same noise-induced problems call for similar answers. "Together we can meet the tough challenges by looking at analog concepts that will make digital circuits better than they seem," he said.

Merkelo expects that at the DesignCon 2003 event in March, there will be a call to develop some standardized ways that ICs can talk to one another without the influence of noise characteristics.

"I think that semiconductor companies are ready to develop some parameters under which their chips can find common ground on the traces of printed-circuit boards and not be hampered by high-frequency anomalies that affect all parts of a system design," he said.