According to Sina Finance, U.S. semiconductor company Cirrus Logic made an unsolicited takeover offer for Synaptics last month in an effort to disrupt Synaptics' previously announced merger deal with Onsemi. Synaptics' updated proxy filing on Thursday referred to the “party A” in the document as Cirrus Logic, and sources said it was still unclear whether Cirrus Logic remained interested in pursuing the acquisition.

The sources said Cirrus Logic's cash-and-stock offer prompted Onsemi to revise the terms of its agreement with Synaptics last week, changing the deal structure from all-stock to all-cash and lifting the per-share offer to $123. Onsemi said in a statement that the adjustment was driven by a third-party “competing unsolicited acquisition proposal,” but it did not disclose the bidder at the time.

The proxy filing showed Synaptics' board carefully evaluated Cirrus Logic's offer and negotiated with the company before concluding that Onsemi's revised bid was in the best interests of shareholders. Onsemi first announced the Synaptics acquisition in June to expand its semiconductor business for smart devices.

Cirrus Logic shares fell about 6% to $106.87 on Friday, giving it a market value of about $5.4 billion. Onsemi shares fell about 2% to $77.53, with a market value of $30.2 billion. Synaptics shares rose 0.6% to $119.82, giving it a market value of $4.8 billion.