FREMONT, Calif. - Dec. 14, 1999 -- Cirrus Logic Inc. (NASDAQ:CRUS) confirmed today that it is continuing to seek a preliminary injunction against SigmaTel Inc. from using the intellectual property protected by U.S. Patent No. 4,851,841(‘841) issued to Crystal Semiconductor. Cirrus Logic anticipates the matter to be heard by the U.S. District Court, Western District of Texas.

Cirrus Logic alleges that certain of SigmaTel’s AC ’97 audio products are infringing upon the ‘841 patent, which was recently determined by the same court to be valid and infringed by two other companies. Cirrus Logic is also seeking damages and a permanent injunction against SigmaTel.

Cirrus Logic has retained the highly experienced patent litigation firm of Vinson & Elkins LLP after the law firm of Brobeck, Phleger & Harrison LLP, which filed the case for Cirrus Logic, was disqualified based on work it had performed for SigmaTel several years ago. “While this development has caused a minor delay in the formal court proceedings, our internal preparations to seek a preliminary injunction early next year are continuing without interruption,” asserted J.P. Violette, Cirrus Logic’s vice president, intellectual property counsel.

Violette noted that the disqualification of Brobeck, Phleger & Harrison LLP does not affect in any way his company’s long-standing relationship with members of the Brobeck firm, nor the substantive claims that his company has made against SigmaTel. “We expect the Brobeck firm to continue working with us on other unrelated litigation proceedings,” said Violette.

Cirrus Logic is a premier supplier of high-performance analog circuits and advanced mixed-signal chip solutions. The company's products, sold under its own name and the Crystal product brand, enable system-level applications in audio, optical storage, and industrial markets. Additional information about Cirrus Logic is available at www.cirrus.com.