Edinburgh, 16 November 2004: Wolfson Microelectronics plc (“Wolfson or “the Company”), a leading supplier of high performance mixed signal semiconductors, has been notified of the findings of an Initial Determination made by an Administrative Law Judge (ALJ) of the U.S. International Trade Commission (ITC) regarding patent infringement allegations made by Cirrus Logic, Inc. (Cirrus).

The Initial Determination has found that Cirrus’ US Patent No 6,492, 928 (the ’928 patent) is unenforceable because highly material prior art was not disclosed to the United States Patent and Trademark Office. Accordingly, there is no restriction on the sale of the allegedly infringing products into the US.

The Initial Determination has found that three Wolfson audio digital-to-analogue converter products infringe Cirrus’ US Patent No 6,011,501 (the ’501 patent). In this case, the ALJ has recommended a limited exclusion order against the importation of these products into the US. The order is limited to “standalone” products and specifically does not extend to end products that incorporate the Wolfson devices.

The findings of the Initial Determination on the ‘501 patent will have no effect on Wolfson’s business. Two of the three affected products were made obsolete in early 2004 due to a lack of market demand. The third product was modified to remove the disputed feature.

The Initial Determination is subject to review by the full Commission of the ITC which is expected to issue its final decision on 14 February 2005.

The Company is maintaining its revenue guidance provided on 11 October 2004 concerning the current financial year.

David Milne, CEO of Wolfson, said: “The initial findings are an endorsement of Wolfson’s stance that the ‘928 patent is unenforceable. Since the Company no longer markets any products affected by the ‘501 patent allegations, the decision will have no effect on our business.”