| Power management is an essential part of the electronic system and is moving in the direction of high integration with the continuously shrinking of the feature size and the rapid development of system-on-chip (SoC). Integrating the power management circuitry and the blocks needing regulated supply voltage on a single chip can not only reduce the chip area and pins and lower the cost of system, but also reduce the crosstalk between them and improve the performance of the system.In this thesis, the advantages and drawbacks of different power circuits are compared and the scheme of power system suitable for MCU application is proposed. Power system designed here consists of two parts, namely, standby mode power circuitry and active mode power circuitry respectively. The former is an ultra-low power quasi-voltage-reference with an output buffer stage, mainly used to guarantee part of memories and the low-frequency oscillator of the chip to work normally in standby mode; the latter is a low dropout regulator (LDO), primarily used to ensure MCU, kinds of memories, high-frequency oscillator and I/O ports to work normally in active mode. When the chip is in active mode, LDO is aroused to provide the internal supply voltage for the chip; when the chip is in standby mode, LDO stops working and the quasi-voltage-reference provides the internal supply voltage for the chip; this can lead to lower average power consumption of the chip.Based on HEJIAN 0.25μm CMOS technology, the two circuits have been designed and simulated. The quiescent current, the maximum output current, output voltage, accuracy and the maximum temperature coefficient of the power circuitry used for the standby mode is 240nA, 100μA,2.1V,±0.15V and 110ppm/℃respectively. Its line regulation and load regulation are 13mV/V and 2.2mV/μA, and its power supply rejection ration (PSRR) is -44dB at low frequency. The quiescent current, the maximum output current, output voltage, accuracy and the maximum temperature coefficient of the power circuitry used for the active mode is 135μA, 20mA,2.4V,±0.1V and 36ppm/℃respectively. Its line regulation and load regulation are 8.3mV/V and -0.24mV/mA, and its PSRR is -56dB at low frequency and -34dB at 1MHz. |
