Design And Optimization Of Single-chip Lightning Protection Circuit

Lightning is an ancient phenomenon of electrostatic discharge.In the earth’s atmosphere,an average of 8 million lightning strikes occur every day,and there are nearly100 lightning strikes per second.An aircraft is struck by lightning on average once a year.The lightning protection module is a functional module that can safely shield huge surge signals without affecting any circuit.For general chips,external high-power TVS or varistors can be used for design.However,there are many kinds of complicated input and output ports in the aircraft.On the one hand,there are a large number of solder joints that cause unreliability,and the module is large in size.On the other hand,it is impossible to find all matching device models.Therefore,facing the trend of miniaturization,integrating a lightning protection circuit with a certain ability inside the chip is an important idea for the development of future aircraft.Aiming at lightning protection for high-speed systems,this article discusses and designs a new-architecture bidirectional TVS,which can be used on some high-speed interfaces or power supplies,such as USB3.0 and Type-C.The characteristics of leakage,interelectrode capacitance,and reverse conduction resistance between the I/O ports are studied through simulation to provide a simulation basis for the design.In this paper,through detailed analysis of the relationship between each current path and device failure,two layout structure layouts under single-layer metal wiring are proposed,and the advantages and disadvantages of the two layouts are analyzed.Based on a domestic 0.5μm process platform,with the support of simulation data,the pull-off and splitting parameters are determined,and the TLP characteristic curves,bidirectional symmetry,capacitance characteristics and system-level verification after packaging of three different parameter cells are analyzed experimentally.It shows the competitiveness of the device among similar products in high-speed lightning protection for small and medium-sized systems.Chapter 22 of the DO-160G standard simulates the transient voltage and current generated by the electromagnetic field generated by the aircraft fuselage by the direct lightning surge in the avionics equipment.It is divided into 5 levels and 4 types according to the installation of the airborne electronic equipment.Waveform.The typical interface lightning protection scheme is a three-level protection circuit.Generally,for integrated anti-lightning devices,the combination of TVS clamp and TBU/current limiting resistor for overcurrent protection becomes the first choice.However,when the voltage difference between the two ends of the TBU is less than 18V（maximum 18V）,it returns to normal.Therefore,the protection of 28V discrete interface chip cannot use TBU for current limiting.In this paper,the research on integrated lightning protection devices is carried out,and the preparation process of high-voltage polysilicon is proposed.The simulation results in a long polysilicon structure with a 2.2μm thick dielectric layer and double trench isolation,which reduces the terminal electric field to 5E16V/cm.This paper presents a design idea of 28V latch-up free SCR,experimentally tested 7.5V SCR devices with different areas,and obtained SCR devices with W=175μm,V_CL=12V,and I_t2=22A.It is planned to use SCR stacking to make it meet the discrete requirements.Standards for protection of input and output ports,and plans to carry out follow-up design and testing for this.Furthermore,this article discusses and designs a new type of bidirectional TVS for high-speed interface circuit lightning protection.It simulates the influence of trap concentration on various indicators and provides simulation basis for the design.In this paper,two layout layouts under single-layer metal wiring are designed.Based on a domestic 0.5μm process platform,a bidirectional SCR device with an inter-electrode capacitance of 0.55p F is obtained through experiments.The simulation has passed the eye diagram verification at 3.3Gbps,and the system-level ESD capability reaches±10k V,lightning surge capacity is greater than 5.26A(V_CL=11V).