Design Of Low Capacitance TVS Diodes For CAN Bus Electrostatic Protection

CAN is a kind of serial communication protocol,which is mainly used to connect sensors and electronic modules of cars and trucks at the beginning of development.Due to the high reliability of data transmission of CAN bus,it has been applied more and more widely in various electrical fields.External electrical transients such as lightning strike and ESD will bring unpredictable damage to the data transmission and hardware of CAN bus.Therefore,a series of protection measures need to be given for CAN bus,such as adding TVS protection device to the port.Based on this,the design and analysis of a TVS diode to protect CAN bus are mainly carried out in this paper.The main work is as follows:1.According to the characteristics of CAN bus and the characteristics of TVS for CAN bus protection,the structure of TVS is proposed and the performance parameters of TVS are determined.Combined with the common capacitance scheme,the series capacitance downdraft scheme and the integrated low capacitance scheme,the design of the low capacitance TVS diode was proposed by combining the general capacitance TVS diode and the integrated capacitance downdraft scheme.After putting forward the structural design scheme,the process scheme of the TVS diode and the integrated capacitance downducter is designed,which lays the foundation for the subsequent simulation and optimization.2.With the help of simulation software,the structure and process of proposed schemes are simulated and the simulation of let TVS diode and integration drop tube's basic parameters,on the volume resistivity of TVS diode and epitaxial layer thickness,diffusion condition,dose and integration drop tube of resistivity and thickness of the epitaxial layer optimization simulation,determine appropriate process adjustment window,Finally,A general capacitance TVS diode with A breakdown voltage of 25.3V,A capacitance of 17.2p F and A leakage of less than 0.1?A were obtained through simulation,as well as an integrated capacitance downdraft with A capacitance of less than3 p F,which met the design requirements as A whole.The layout of the device was also drawn.Finally,the layout plan and process plan are imported to the foundry.3.After the experiment,the chip samples were encapsulated and sampled for testing.Finally,A dual-channel bi-directional low capacitance TVS device with capacitance less than 3p F,breakdown voltage between 28.35 V and 28.67 V,leakage current less than0.005?A,maximum peak pulse current more than 5A,residual voltage less than 40 V,and ESD contact discharge capacity more than ±30k V was realized.In line with the design indicators.The work done in this paper has laid a solid foundation for the production of TVS for CAN bus protection.Meanwhile,we hope to realize the domestic replacement of low capacitance TVS products as soon as possible.