The design of DC-DC converter with DT-CMOS for portable terminal

The high efficiency power management IC (PMIC) with switching device is presented in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. Dynamic threshold voltage CMOS (DT-CMOS) with low on-resistance is designed to decrease conduction loss. The threshold voltage of DT-CMOS drops as the gate voltage increases, resulting in a much higher current handling capability than standard MOSFET. The control parts in buck converter, that is, PWM control circuits consist of a sawtooth generator, a band-gap reference circuit, an error amplifier and a comparator circuit as a block. The sawtooth generator is made to have 1.2 MHz oscillation voltage (VDD:3.3 V). The comparator is designed with two stage OP amplifier. And the error amplifier has 70 dB DC gain and 64° phase margin. DC-DC converter, based on voltage-mode PWM control circuits and low on-resistance switching device, achieved the high efficiency near 95% at 100 mA output current. And DC-DC converter is designed with low drop out regulator (LDO regulator) in stand-by mode which fewer than 1 mA for high efficiency.