Design Of The ESD And EOS Protection For Isolated CAN Transceivers

Isolated controller area network(CAN)transceivers are widely used in automotive electronic communication and data transmission due to their advantages of high electromagnetic compatibility,high anti-interference and low radiation.However,isolated CAN transceivers easily suffer the risk of electrostatic discharge(ESD)and electrical overstress(EOS).It may fail in communication or data transmission,or even be damaged.Most of the existing isolated CAN transceivers often use external discrete ESD or EOS protection circuits,resulting in a large area,poor portability and low efficiency.For the ESD/EOS protection requirements of isolated CAN transceivers,a series of ESD/EOS protection devices are designed and fabricated in 0.18μm Standard CMOS Process.Furthermore,the working principles and electrical properties of the device are discussed by Sentaurus simulation software and a transmission line pulse(TLP)system.The main research contents of the thesis are as follows:Firstly,the internal circuit modules and working principles of isolated CAN transceivers are introduced.The common test standards,protection levels,design rules and process of ESD/EOS protection are described.The working principles,advantages and disadvantages of traditional diodes,field effect transistors(MOSFET,short name MOS)and silicon controlled rectifiers(SCR)as ESD/EOS protection units are analyzed.Secondly,ESD/EOS protection solutions are designed for the ports of single power domain in the isolated CAN transceiver.(1)For multiple ESD stress directions in 5 V logic circuits,the three-terminal bidirectional SCR(3TD-SCR)triggered by zener diode is proposed.3TD-SCR integrates three ports in the same structure with a special well segment layout.Compared with FN-DTSCR,3TD-SCR greatly reduces chip area and has a low clamping voltage of 6.5 V.(2)For the EOS protection requirements of 5 V bus power port,an embedded dual MOS-assitanted trigger SCR(GDSCR-EMOS)is designed.The introduced dual gate coupling technology is beneficial for narrowing the voltage snapback magnitude.Compared with conventional SCR,the trigger voltage of GDSCR-EMOS is reduced to 10.3 V,and the holding voltage is increased to 6.1 V.Finally,ESD/EOS co-design is proposed around ESD/EOS events between two power domains of isolated CAN transceivers.By introducing the gate coupling effect and special layout,a novel DTSCR with embedded MOS and island diodes(DTSCR-EMOS-ID)was designed and fabricated.Compared with ordinary DTSCR,the trigger voltage of DTSCREMOS-ID decreases about 20% because of the extra gate coupling effect.And it has multiple current discharge paths strongest discharge ability.The DTSCR-EMOS-ID shows much better ESD performance such as its turn-on time is about 1.6 times faster than conventional DTSCR and LVTSCR.The DTSCR-EMOS-ID also presents a small turn-on resistance of 8 mΩ/μm,a small parasitic capacitance of 43 f F and a low clamping voltage of 3.6V.The proposed DTSCREMOS-ID can be widely used as an effective ESD protection device for the isolated CAN transceiver,without the limitation of the fabrication process.