Billionaire Al Mann has agreed to sell his Valencia medical device maker, Advanced Bionics Corp., to a large Swiss hearing aid firm for $489 million in cash, the companies announced Monday.

Sonova Holding AG, of Staefa, Switzerland, which currently has a 24 percent share of the world’s hearing aid market, will buy Advanced Bionics, a leading developer of cochlear implants. The electronic devices, which Sonova does not make, are surgically implanted inside the ear to stimulate auditory nerves, thus allowing some deaf people to hear sounds.

Mann founded Advanced Bionics in 1993 and sold it Boston Scientific Co. in 2004. After years of litigation over how Boston Scientific was fulfilling terms of the deal, Mann bought back the company in 2007. It now has 660 employees and in fiscal 2008 had sales totaling more than $117 million. It has an 18 percent share of the worldwide cochlear implant market, which is estimated to be more than $750 million.

“Sonova was attracted to our company for our advanced technology, commitment to our patients and our potential for expansion,” Chief Executive Jeffrey Greiner said in a statement. “Not only will we continue to grow under the leadership of Sonova, but we have taken an enormous step toward ensuring that AB remains the industry’s performance leader, now and in the future.”

Sonova, which markets the Phonak line of micro hearing systems, said it plans run its new acquisition as an independent division and keep operations in California. This fall Advanced Bionics moved its corporate headquarters out of Mann Biomedical Park and into a larger 144,000-square-foot facility in the Summit Oaks complex, also in Valencia.

Manufacturing operations, now in Sylmar, are expected to be consolidated at Summit Oaks by 2012, pending regulatory approval.