SAN DIEGO, May 22 -- After four years at the helm of Cohu Inc. Charles A. Schwan, 61, will retire as the company's CEO on June 30 of this year. Schwan has served in a variety of management positions at Cohu since 1971 and will stay on as chairman of the company's board of directors. Cohu's current president and COO, James A. Donahue, will be named the company's president and CEO upon Schwan's retirement. Donahue has been Cohu's president and COO since 1999 after working for several years as president of the company's subsidiary Delta Design.