A switching regulator and lightning protector for a subscriber line interface circuit

Two monolithic ICs, a switching regulator and a crowbar protector circuit fabricated in a 90-V complementary bipolar technology are described. These devices enhance the performance of a basic subscriber-line interface circuit (SLIC) by extending the range to the customer so that 20-mA DC feed current can be supplied to a 2800-/spl Omega/ loop without the need for a -72-V office battery. The power dissipation of the entire SLIC subsystem is at most 1.5 W for any length of subscriber loop. All circuitry is robustly protected from foreign 60-Hz and lightning voltages.