Data Sheet
October 1997
L7591 Subscriber Line Interface Circuit Protector
Features
Description
s
Shunts lightning pulses to ground
— Positive or negative 30 A, 10 x 1000 µs
— Positive or negative 40 A, 5 x 320 µs
— Positive or negative 80 A, 2 x 10 µs
s
Power-cross protection
— 3.5 APEAK, 50 Hz to 60 Hz, 1 s
— 5.0 APEAK, 50 Hz to 60 Hz, 10 ms
s
Gate trigger current, 15 mA max
s
Up to –80 V capability
s
Holding current, 150 mA min
The L7591 Subscriber Line Interface Circuit (SLIC)
Protector is designed to protect line-feed circuitry
from fault-induced lightning and power-cross surge
pulses. If a fault current forces TIP and/or RING to a
more negative voltage than VS, current is conducted
through the trip circuit. When the specified trip current level is reached, transistors PNPN1 and/or
PNPN2 will turn on and "crowbar" the majority of the
current to ground. If similar pulses force TIP and/or
RING to a more positive state than ground, diodes
D1 and/or D2 will conduct the pulse to ground. The
L7591 SLIC Protector is available in an 8-pin, plastic
DIP (L7591AB) and in an 8-pin, plastic SONB package (L7591AS).
Pin Information
Table 1. Pin Description
(Applies to DIP and SONB packages)
Pin
Symbol
1
2
TIP
VS
3
4
5
—
RING
PR
6
GND
7
GND
8
PT
TIP
TRIP
CIRCUIT
Name/Function
Tip signal from customer.
Supply voltage to gate
(–20 V to –80 V).
Test Point, do not use.
Ring signal from customer.
Protected ring signal to line-feedcircuitry.
Device ground/fault current
return.
Device ground/fault current
return.
Protected tip signal to line-feed
circuitry.
Note: Pins 1 and 4 must always be connected to the protection
resistors shown in Figures 4 and 5 (Line Feed Circuitry). The
SLIC can be connected either to the protected outputs (pins
5 and 8) or to the inputs (pins 1 and 4).
8 PT
1
D1
PNPN1
VS
2
TEST
POINT
3
7 GND
6 GND
PNPN2
TRIP
CIRCUIT
RING
D2
5 PR
4
12-1590 (C)
Figure 1. Functional and Pin Diagram
