High-voltage circuits for power management on 65 nm CMOS

Abstract

This paper presents two high-voltage circuits used in power management, a switching driver for buck converter with optimized on-resistance and a low dropout (LDO) voltage regulator with 2-stacked pMOS pass devices. The circuit design is based on stacked MOSFETs, thus the circuits are technology independent. High-voltage drivers with stacked devices suffer from slow switching characteristics. In this paper, a new concept to adjust gate voltages of stacked transistors is introduced for reduction of on-resistance. According to the theory, a circuit is proposed that drives 2 stacked transistors of a driver. Simulation results show a reduction of the on-resistance between 27 and 86 % and a reduction of rise and fall times between 16 and 83 % with a load capacitance of 150 pF at various supply voltages, compared to previous work. The concept can be applied to each high-voltage driver that is based on a number (N) of stacked transistors. The high voltage compatibility of the low drop-out voltage regulator (LDO) is established by a 2-stacked pMOS transistors as pass device controlled by two regulators: an error amplifier and a 2nd amplifier adjusting the division of the voltages between the two pass transistors. A high GBW and good DC accuracy in line and load regulation is achieved by using 3-stage error amplifiers. To improve stability, two feedback loops are utilized. In this paper, the 2.5 V I/O transistors of the TSMC 65 nm CMOS technology are used for the circuit design.