SAN FRANCISCO -- Saying the proposed purchase price was too low, Altium today rejected an acquisition bid from rival Autodesk, but left the door open to future offers. 

Autodesk confirmed a nonbinding proposal to acquire all outstanding shares of common stock of Altium for AUD$38.50, a 41.5% premium over Altium's closing price on Jun. 4 and a premium of over 47.4% to the one-month volume-weighted average price. About one-fifth of Altium's stock is held by insiders. Based on 131 million shares outstanding, the value of the deal is just over AU$5 billion, or US$3.91 billion. Autodesk said it would finance the transaction using cash on hand and debt financing.

Altium rejected the proposal, however, saying the price significantly undervalues its prospects. Alitum said it will continue to review all potential strategic alternatives.

The acquisition of San Diego-based Altium would advance Autodesk's strategy to converge design and make through a unified design, engineering and manufacturing cloud platform that enables greater productivity and sustainability for its customers, the company said in a statement. Autodesk believes Altium's solutions would be complementary to its portfolio, creating unique opportunities for customers while delivering significant, certain and immediate value to Altium's shareholders.

Autodesk's proposal is subject to a number of conditions including, among them due diligence, unanimous approval by the Altium board, Altium shareholder approval and court approval, among others. the firm said it does not intend to make any additional comments, pending a definitive agreement between the EDA companies.

Autodesk is a smaller player in printed circuit board design, having acquired the Eagle PCB line from Cadsoft for about $26 million in June 2016. 

The last major deal in EDA was Siemens $4.5 billion acquisition of Mentor, which included semiconductor design and manufacturing tools in addition to its PCB software.

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