[PDF] USB Hardware Design Guide - silabs The USB peripheral embedded on these devices include the USB PHY and an internal voltage regulator, thus requiring only a minimum number of external components. The on-chip voltage regulator's primary purpose is to power the EFM32 USB PHY. But as it can deliver USB Charger Schematic Design - ieeeeley USB Charger Schematic Design. USB car chargers convert an automobile's 12V DC outlet (originally for lighting cigarettes!) into a regulated 5V DC supply that can charge USB devices, like smartphones and tablets. These chargers are available online for under $10; you can often find them for even less.