The Miami Dolphins will have to win voter approval of tax dollars for Sun Life Stadium, with team executives agreeing to a referendum on the controversial plan, sources close to the matter said Saturday. Sen. Oscar Braynon, the Miami Gardens Democrat sponsoring a bill to bring Sun Life new state and county subsidies, will change the proposed legislation to require a countywide vote on the plan, a source familiar with the Dolphins’ lobbying efforts said. The Dolphins and County Mayor Carlos Gimenez plan to announce the referendum agreement Monday, sources said. The Dolphins hope to get the issue before voters by May 22, when the NFL is expected to pick the host city for the 2016 Super Bowl. The Dolphins have cited that game, the 50th in NFL history, as the reason to push for a quick decision on tax dollars to pay for about half of a proposed $400 million renovation.