A mixed EFL I2L digital telecommunication integrated circuit

A bipolar digital telecommunications circuit has been designed in the OXIL technology as part of a VLSI upgrade of an existing digital switching circuit. The chip is unique in its exploitation of the OXIL oxide isolated process which allows both high gain "up" and "down" devices used for I²L and EFL (emitter function logic), respectively. This allowed the circuit designers to tailor power consumption, circuit speed, and gate density as needed. In particular, the high speed properties of EFL were utilized in the control section to provide accurate timing signals and satisfy tight propagation delay requirements in the register section. I²L, because of its greater density and low power, was used in the gate intensive register sections. Another novel feature of this device was the treatment of bus lines (up to 250 fanout) such as clock, clear, etc., in the I²L sections. The common multiline I²L drive problem has been overcome here by using high drive translators from EFL circuitry and a single pullup resistor per bus line to provide switched currents to all gates on that line.