Touchscreen chipmaker Synaptics Inc said it would buy the sole supplier of display chips for the iPhone for $475 million, potentially winning back Apple Inc as a customer. Synaptics’s shares jumped 19 percent in extended trading after the company also raised its revenue forecast for the fourth quarter ending June 30. Reuters had reported last month that Apple had failed to make progress in talks to buy Renesas Electronics Corp’s majority stake in the Japanese chipmaker Renesas SP Drivers Inc, paving the way for Synaptics to strike a deal. Synaptics would integrate its touch technology with Renesas’ display drivers into one chip, saving manufacturing costs, Feltl & Co analyst Jeffrey Schreiner said.