Low-cost, Low Power, Highly Integrated Single-chip Power System Design

This article start with the actual design requirements of power circuit in MCU chip development, the main technical problems are three points:high integration that cap-less structure, very low standby current in low power consumption mode, and low cost in chip area. Base on that judgment, the power circuit structure of the mainstream had a full analysis and argument, their strengths and weaknesses were compared, then made trade-offs to construct the schematic structure.Power supply circuit can be divided into two types of switching power supply and linear power. According to the different energy storage devices, switching power supply divided into PWM of PFM circuits depend on inductor device of charge pump circuit depend on capacitor device. Linear power supply circuit can also divided into several forms according to the error amplifier forms. Their respective advantages and disadvantages are different, such as PWM circuits has a good current conversion efficiency in high-power loading case, and linear circuits has the excellent EMI characteristics. In this article design requirements face the limit that wide voltage swing input, and without the constraints of external devices, it is difficult to complete circuit design just using a single structure. Therefore, a composite circuit structure must be used in the final power system.Based on full discussion of the characteristics of each type of power supply circuit and find their advantages, the final power supply circuit structure is decided as the linear power with charge pump circuit to expand it's input voltage swing, it's output stage used source follower to improve the AC dynamic characteristics, in low power mode, hysteretic control mode is used to make strictly control of the standby current.When objectives and structure of the circuit system are established, thesis futher clarify the definition of each block circuit design and do the simulation, finally get the complete power system designAfter design and layout, the chip tapped out, samples were verified proved that design goals successfully achieved.