Improving the low temperature lightning surge performance of thyristor overvoltage protectors

Protectors used at the subscriber´s end of the telephone line need even functionality down to -40°C. Characteristically, the surge capability of thyristors decreases with decreasing temperature. Factors which determine simulated lightning surge performance at reduced temperatures are identified. A protector design capable of surviving 100 A, 10/1000 μs at -40°C is shown to be viable. There is a design compromise between the surge performance and the value of V_(BO) relative to V_DRM; those factors that increase surge generally degrade (increase) V_(BO). The optimum design used high dot density, buried breakdown pad, and planar junction termination