https://www.theverge.com/2017/11/30/16719724/apple-power-management-chips-dialog-semiconductor

Apple is designing its own power management chips for iPhones, and plans to stop relying on its current supplier Dialog Semiconductor, anonymous sources told Nikkei Asian Review.

One anonymous source said: “Based on Apple's current plan, they are set to replace around half of its power management chips to go into iPhones by itself, starting next year.” Another person said the chips might not be ready until 2019.