People familiar with the matter said that U.S. semiconductor company Cirrus Logic launched an unsolicited acquisition bid for Synaptics last month, seeking to disrupt the latter's previously announced merger with onsemi.

Sources said that the "Party A" mentioned in the shareholder proxy statement updated by Synaptics on Thursday is Cirrus Logic. The sources added that it is not yet clear whether Cirrus Logic still intends to pursue the acquisition.

Cirrus Logic's offer took the form of cash plus stock, prompting onsemi to revise the terms of its agreement with Synaptics last week. onsemi changed the deal structure from all-stock to all-cash and adjusted its per-share offer to $123.

In a statement, onsemi said the adjustment stemmed from a "competing unsolicited acquisition proposal" from a third party, but it did not disclose the identity of the bidder at the time. Representatives for Austin-based Cirrus Logic and Scottsdale, Arizona-based onsemi declined to comment. A spokesperson for San Jose, California-based Synaptics did not immediately respond to a request for comment.

The proxy statement shows that Synaptics' board carefully evaluated Cirrus Logic's acquisition offer and negotiated with it, ultimately concluding that onsemi's revised offer best served shareholder interests.

onsemi first announced the deal to acquire Synaptics in June, aiming to expand its semiconductor business for smart devices.

At Friday's close, Cirrus Logic shares fell about 6% to $106.87, giving it a market value of about $5.4 billion. onsemi shares fell about 2% to $77.53, giving it a market value of $30.2 billion. Synaptics shares rose 0.6% to $119.82, giving it a market value of $4.8 billion.