Subscriber line interface circuit with reduced on-chip power dis

Details Subscriber line interface circuit with reduced on-chip power dis Subscriber line interface circuit with reduced on-chip power dis

1993-03-12

1995-06-27

Dwyer, James L.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379398, 379399, H04M 1900

Patent

active

054286824

ABSTRACT:
A subscriber line interface circuit is provided that includes an output stage having a pair of differential transconductance amplifiers to drive the tip and ring lines of a telephone exchange. The output stage includes circuitry that advantageously reduces the power dissipated within the integrated circuit when the subscriber loop impedance is relatively low. As a result, heat generation within the integrated circuit is reduced. Circuit reliability may therefore be enhanced and fabrication and packaging costs may be reduced. In one embodiment, an off-chip resistor is coupled from an output line of the ring line amplifier to the negative voltage rail. When the loop impedance is low, a relatively large voltage drop is established across the resistor which therefore absorbs a greater percentage of the loop current. Since the resistor is provided off-chip and diverts current that would otherwise flow through the ring-line amplifier, the overall heat dissipated within the integrated circuit is reduced.

REFERENCES:
patent: 4677667 (1987-06-01), Burns
patent: 4677669 (1987-06-01), Kawami et al.
patent: 4866768 (1989-09-01), Sinberg
patent: 4879746 (1989-11-01), Young et al.
patent: 5046089 (1991-09-01), Pariani et al.
Electronic Design, Jul. 11, 1994 vol. 42, No. 14, article entitled "High-Voltage Bonded-Wafer ICs Create First SLIC to Switch The 93-V RMS Phone-Line Ring Voltage on-Chip, Eliminating PABX Relays", written by Frank Goodenough, pp. 55-64, Cover Page, Table of Contents.
HC-5506 Specification for Dual Subscriber Line Interface Circuit (DSLIC), Harris Semiconductor, Advance Information, Jun. 1994, 16 pages.

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