TISP6L7591

The TISP6L7591 is a dual forward-conducting buffered p-gate overvoltage protector. It is designed to protect monolithic SLICs (Subscriber Line Interface Circuits) against overvoltages on the
elephone line caused by lightning, a.c. power contact and induction. The TISP6L7591 limits voltages that exceed the SLIC supply rail voltage.

The SLIC line driver section TISP6L7591 is typically powered from 0 V (ground) and a negative voltage, V_S, in the region of -20 V to -80 V. The protector gate is connected to this negative supply. This references the protection (clipping) voltage to the negative supply voltage. The negative protection voltage will then track the negative supply voltage and the overvoltage stress on the SLIC is minimized.

Positive overvoltages are clipped to ground by diode forward conduction. Negative overvoltages are initially clipped close to the SLIC negative supply rail value. If sufficient current is available from the overvoltage, then the protector will switch into a low voltage on-state condition. As the overvoltage subsides the high holding current of TISP6L7591 crowbar prevents d.c. latchup.

These monolithic protection devices are fabricated in ion-implanted planar vertical power structures for high reliability and in normal systemoperation they are virtually transparent. The TISP6L7591 is available in 8-pin plastic small-outline surface mount package.