The deadline for a proposed merger between Phoenix-based ON Semiconductor and Fairchild Semiconductor has been extended into May.

ON Semiconductor offered to buy San Jose-based Fairchild for $2.4 billion in November, but the deal is still seeking regulatory approval. According to the U.S. Securities and Exchange Commission, the parties on Friday requested an extension of the offer to May 12.

Fairchild operates a production facility in South Portland that employs more than 500 workers. The plant on Western Avenue is part of Fairchild’s Analog Power Signal and Solutions Division, and makes analog switches, USB, converters and other building blocks of digital circuitry. The company sells components used in cars, smartphones, appliances and other consumer products. It reported revenue of $1.37 billion in 2015.

Betsy Van Hees, a semiconductor analyst for Wedbush Securities, said these types of delays are not unusual in a merger where there are multiple regulatory hurdles to clear.

The deal was further complicated when a Chinese investment group made a bid for Fairchild, offering $21.70 per share, which topped ON’s offer of $20 per share. In February, Fairchild management declined the offer from China Resources Microelectronics Ltd. and Hua Capital Management Co. without specifying why, but analysts surmised it was because the deal wouldn’t receive U.S. regulators’ blessing.

Van Hees said there’s been a tremendous amount of movement in the worldwide semiconductor market as companies acquire one another rather than grow organically. Dealogic, a financial analysis firm, identified $104 billion in chip company deals in 2015 alone, compared with $38 billion in 2014.

“There’s been a lot of mergers and acquisitions in the sector,” Van Hees said, “and China wants to be part of that.”

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