A 3GHz Switching DC-DC Converter Using Clock-Tree Charge-Recycling in 90nm CMOS with Integrated Output Filter

A 90nm buck converter is intended for complex multi-core ICs. Using the 3GHz system clock for switching reduces the area to 0.27mm² and allows the output filter to be integrated. Efficiency is increased by recycling clock charge and delivering it to the load instead of ground. A dedicated 3GHz clock circuit driving 12pF consumes 39.9mW. In contrast, a combined clock and converter circuit consumes 56.2mW and delivers 25.7mW at the converter output. Regulation is achieved through PWM of the clock. The circuit converts 1.0V to between 0.5 to 0.7V at 40 to 100mA.