An 18 V Input 10 MHz Buck Converter With 125 ps Mixed-Signal Dead Time Control

A highly integrated synchronous buck converter with a predictive dead time control for input voltages >18 V with 10 MHz switching frequency is presented. A high resolution dead time of ~125 ps allows to reduce dead time dependent losses without requiring body diode conduction to evaluate the dead time. High resolution is achieved by frequency compensated sampling of the switching node and by an 8 bit differential delay chain. Dead time parameters are derived in a comprehensive study of dead time depended losses. This way, the efficiency of fast switching DC-DC converters can be optimized by eliminating the body diode forward conduction losses, minimizing reverse recovery losses and by achieving zero voltage switching. High-speed circuit blocks for fast switching operation are presented including level shifter, gate driver, PWM generator. The converter has been implemented in a 180 nm high-voltage BiCMOS technology. The power losses were measured to be reduced by up to 31% by the proposed dead time control, which results in a 5.3% efficiency increase at VIN =18 V, VOUT =5 V, and 0.45 A load. At VIN =12 V, the peak efficiency is 81.2% with an efficiency improvement of 6% with dead time control.