March 21 (Reuters) - Israeli advertising technology firm ironSource said on Sunday it has agreed to go public through a merger with a blank-check company backed by U.S. private equity firm Thoma Bravo, valuing the business at $11.1 billion.

The deal with Thoma Bravo Advantage, a special purpose acquisition company (SPAC), is expected to provide ironSource up to $2.3 billion in cash proceeds, including an oversubscribed PIPE (private investment in public equity) of $1.3 billion and $1 billion of cash held in the trust account of Thoma Bravo Advantage.

ironSource provides developers a platform to acquire users and display ads within mobile-phone games. The merger values ironSource at considerably more than the $1.56 billion the company was worth in its most recent private funding round in 2019.

Co-founder and Chief Executive Tomer Bar Zeev said ironSource had decided to pursue a traditional initial public offering (IPO) but changed course when a mutual friend asked him to take a call with Thoma Bravo Advantage Chairman Orlando Bravo.

"I immediately understood we shared the same views about how to build a company, how to run a company," Bar Zeev said in an interview.

This is the first SPAC deal for Thoma Bravo, which has around $73 billion in assets under management and focuses on investing in software and technology.

A SPAC is a shell company that raises funds in an IPO with the aim of acquiring a private company, which then becomes public as result of the merger.

Thoma Bravo Advantage, which completed its IPO on the New York Stock Exchange in January, was attracted to ironSource given the market it operates in, its management team and its business model, Bravo said in an interview.

"What these public equity vehicles provided us, is the ability to target companies that our private equity business is not targeting," said Bravo, who will join ironSource's board on the closing of the deal.

Goldman Sachs & Co. LLC, Jefferies LLC and Citigroup Global Markets Inc are financial advisers to ironSource. (Reporting by Noor Zainab Hussain and Aishwarya Nair in Bengaluru, and Joshua Franklin in Boston; Editing by Peter Cooney, Diane Craft and Daniel Wallis)