AUSTIN, Texas--Sept. 10, 1999--Cirrus Logic Inc. (NASDAQ:CRUS) today announced that its Crystal Semiconductor Division has filed suit against SigmaTel Inc. for infringement of selected mixed-signal patents. The suit has been filed in the U.S. District Court for the Western District of Texas. Both Cirrus Logic's Crystal Division and SigmaTel have principal business offices in Austin, Texas.

One of the patents-in-suit (U.S. Patent 4,851,841 entitled "Gain Scaling of Oversampled Analog-to-Digital Converters'') was recently adjudicated as valid and infringed in the recent lawsuit against OPTi Inc. (Milpitas, Calif.), TriTech Microelectronics Pte Ltd. (Singapore) and TriTech Microelectronics International, Inc. (San Jose, Calif.).

In that action, a jury returned an award of $48.5 million, which was later reduced to $20M. Subsequently, Cirrus Logic was awarded an additional $3.8 million in attorney's fees directed at the TriTech companies. A permanent injunction imposed against Opti and the TriTech companies prohibits the sale of numerous infringing audio products in the United States.

Cirrus Logic holds seminal patents in mixed-signal technology and has successfully prosecuted companies who have infringed its audio patent portfolio in two separate court actions during the past six years. Among the SigmaTel products cited in the action are the STAC9704/07 audio codecs as well as the related family of codec and analog front-end modem chips (STAC9700, STAC9705, STAC9708/11, STAC9721/23).

Cirrus Logic is seeking a preliminary injunction to enjoin the infringing products from being manufactured, used, sold, or imported in the United States, as well as permanent injunctive relief and damages.

Cirrus Logic anticipates that its request for preliminary injunction will be heard within the next six months. In order to prevail in its request for preliminary injunctive relief, Cirrus Logic will need to show that there is a reasonable likelihood of success on the merits and that it is being irreparably harmed by SigmaTel's infringement.

Certain of the SigmaTel products that are cited to infringe are sold into the audio IC market where Cirrus Logic's Crystal Division has been an innovator since the mid-1980s and is currently the market leader. In a recent market research report published by Forward Concepts (Tempe, Arizona), Cirrus Logic was named the overall market leader in the $1.6 billion 1998 market for audio ICs.

Forward Concepts estimates this market which encompasses personal computer, consumer and professional segments -- will grow at a compounded annual rate of 18% to the $3.6 billion level by 2003.

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 mass storage, audio and precision data conversion. Additional information about Cirrus Logic is available at www.cirrus.com.

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