Federal antitrust regulators have declined to review the proposed $489 million acquisition of Camarillo’s Vitesse Semiconductor by Orange County competitor Microsemi Corp. A 15-day waiting period required under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 before a deal can close expired on Tuesday without the Federal Trade Commission or antitrust division of the Justice Department making any move to block the merger. Typically regulators seek more information about deals from the companies involved during this period if there are any antitrust questions. Microsemi, in Aliso Viejo, announced March 18 it would acquire Vitesse in an all-cash transaction valued at $5.28 a share. The deal is expected to close before June 28. Vitesse supplies integrated circuits for the telecommunications carriers, Internet providers and corporations. In the past year the company has made moves to supply wireless connection between devices in both industrial and consumer applications, the so-called “Internet of Things.” It has about 350 employees. Microsemi supplies integrated circuits to telecommunications, defense, security, aerospace and industrial markets. The company has more than 3,000 employees. However, it seemed unlikely regulators would take much interest in the deal. Both companies are a fraction of the size of rivals such as Broadcom Corp. in Irvine, which had revenue of $8.4 billion last year. By comparison, Microsemi and Vitesse had combined revenue of about $1.2 billion. Shares of Microsemi closed up 86 cents, or about 2.5 percent, to $35.81. Vitesse shares closed down a penny to $5.26. Both trade on the Nasdaq.