Parasitic capacitance reduction for a Bi-directional floating-base-PNP ESD device for CAN Bus

As the transmission rates increase on the communication buses, the parasitic capacitance induced by large Electro-Static Discharge (ESD) protection devices raises challenges for normal operation of these buses. This is further challenging for high voltage systems like the Controller Area Network (CAN) bus used in automotive electronics. In order to meet the requirements of higher speed communication bus ESD protection, this paper showcases techniques for parasitic capacitance reduction without degrading the ESD performance of the clamp. The bidirectional floating base PNP clamp is designed for CAN bus in 0.13 μm foundry technology. Optimized structures are proposed to reduce the parasitic capacitance while maintaining the ESD robustness of the clamp. Up to 49% reduction on metal capacitance was achieved by rerouting the metal layers, and junction capacitance was reduced by lowering the doping concentration in the floating base and emitter finger. The measured capacitance show a reduction of up to 24% reduction in total capacitance while maintaining the same ESD performance.