Description
The TISP61089B is a dual forward-conducting buffered p-gate thyristor (SCR) overvoltage protector. It is designed to protect monolithic SLICs (Subscriber Line Interface Circuits) against overvoltages on the telephone line caused by lightning, a.c. power contact and induction. The TISP61089B limits voltages that exceed the SLIC supply rail voltage. The TISP61089B parameters are specified to allow equipment compliance with Bellcore GR-1089-CORE, Issue 2 and ITU-T recommendations K.20, K.21 and K.45.
The SLIC line driver section is typically powered from 0 V (ground) and a negative voltage in the region of -20 V to -150 V. The protector gate is connected to this negative supply. This references the protection (clipping) voltage to the negative supply voltage. The protection voltage will then track the negative supply voltage and the overvoltage stress on the SLIC is minimized.