Overcurrent and overvoltage protection method and architecture for a tip and ring subscriber line interface circuit

摘要

A circuit for protecting a plurality of tip/ring SLIC cards during over current or over voltage conditions. A diode pair corresponding to each tip/ring pair provides positive voltage over voltage protection in a negative powering scheme. Two thyristors provide negative over voltage protection. Tip conductors of half of the SLICs connect to the cathode of one of the thyristors. The ring conductors corresponding to each of these tips connects to the cathode of the other, or second, thyristor. The remaining tips are connected to the cathode of the second thyristor. The rings corresponding to these remaining tips connect to the cathode of the first thyristor. This alternating connection of tips and rings provides twice the current capacity of a single thyristor, while cutting in half the potential holding current through either of the thyristors, thus increasing the likelihood of automatic return to normal operation following cessation of negative over voltage.