Back-end Design And Implementation Of A High-power And High-integration PMIC

PMIC(Power Management Integrated Circuit)is a highly integrated power management solution for mobile devices.It integrates a number of separated traditional power management chips into a single power management unit to achieve higher efficiency and lower power consumption while supporting more functions.This paper based on a real project "A Multi-channel Power Management IC PMIC9***” which the author participated in.It includes the research and development of a new switch MOSFET,the protection ring technology,and the full custom analog layout technology etc.Eventually,the project has been completed successfully.In this paper,the author analyzed the LDNMOS from a standard BCD process in two ways of device structures and application environments.Due to LDNMOS natural drain structure,the HVNW acts as the drain and the isolation from P-substrate.For the application of BUCK circuit,the parasitic PNP can easily introduce the noise from the switch MOSFET into the P-substrate,which has a serious impact on the accuracy and stability of the analog part of the circuit.The author analyzed the working status of LDNMOS under different application conditions by numerical simulation,and reached the conclusion that the parasitic PNP structure introduces noise into the substrate.In order to overcome the drawbacks of LDNMOS for BUCK circuit,this paper presents a new type of double-gate MOSFET(DGMOS),which is independent of the device and avoids triggering the parasitic device.Based on the double-gate structure,the width of the drift area can be easily adjusted to get devices with different break-voltages,and the process of DGMVN is compatible with a standard BCD process.In this paper,the author systematically summarized the structures and functions of the conventional protection rings with fixed potentials,analyzed the various kinds of noise and its forming mechanism in detail,and pointed out that the conventional protection rings with fixed potentials can not meet the request of the high-power,high-integration and multi-channel power management IC.Based on the theoretical research of a floating protection ring from a paper,the author found a new type of floating ring structure with a balance between the area and performance after designing,testing and optimizing the layouts.The marked difference of the floating protection ring from the conventional protection rings is its active mode of collecting redundant carriers,instead of a passive mode for conventional protection rings.In the later chapter,this paper shows the layout work process.The author summarized the key points,work skills and related knowledge of layout design.As an engineering thesis,this paper aims to solve the issues encountered in practical work.The description of the relevant contents and solutions is based on BCD processes specialized,products which the author involved in,and applications of the kinds of PMIC.The conclusion does not have universal significance,but if reader suffers the similar issues,this thesis still has a certain reference value.