TISP61512P

The TISP61511D and TISP61512P are dual forward-conducting buffered p-gate overvoltage protectors. They are designed to protect monolithic Subscriber Line Interface Circuits,SLICs, against overvoltages on the telephone line caused by lightning, ac power contact and induction. The TISP61511D and TISP61512P limit voltages that exceed the SLIC supply rail voltage.

The SLIC line driver section TISP61511D and TISP61512P is typically poweredfrom 0 V (ground) and a negative voltage in the region of -10 V to -70 V. The protector gate is connected tothis negative supply. This references the protection (clipping) voltage to the negative supply voltage. As theprotection voltage will track the negative supply voltage the overvoltage stress on the SLIC is minimised.

Positive overvoltages TISP61511D and TISP61512P 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 crowbar into a low voltage on-state condition. As the current subsides the high holdingcurrent of the crowbar prevents d.c.latchup.

These monolithic protection devices TISP61511D and TISP61512P are fabricated in ion-implanted planar vertical power structures for high reliability and in normal system operation they are virtually transparent. The buffered gate design reduces the loading on the SLIC supply during overvoltages caused by power cross and induction.