An optically-coupled high-voltage p-n-p-n crosspoint array

A solid-state crosspoint array compatible with electromechanical switches has been developed in order to realize high-performance telephone exchange networks. The optically-coupled high breakover voltage crosspoint array discussed in this paper has achieved complete isolation of the speech path from the triggering circuit while it can be triggered directly by a transistor-transistor logic (TTL) level signal from the control circuit. The crosspoint array has a unique photo-coupling structure which allows four p-n-p-n elements to be triggered effectively by only one LED, maintaining up to 200 V/0.1 /spl mu/s dv/dt characteristics. It provides breakover voltage of up to 450 V, gate trigger LED current less than 20 mA, ON-state resistance within 4.5 /spl Omega/ and OFF-state capacitance less than 7 pF. The matrix arrangement is a 1/spl times/4 configuration; it is composed of a two wire bidirectional circuit and packaged in a 16-pin ceramic DIP. These device characteristics make possible the realization of solid-state crosspoint array practically compatible with the conventional electromechanical switch, particularly meeting requirements of miniaturization, low-power dissipation, and inexpensive construction. Accordingly, direct interface with conventional telephone sets is possible.