CMOS-interfaceable ECL integrated circuit with tri-state and adjustable amplitude outputs

摘要

An improved ECL circuit, based upon an ECL circuit of conventional design, functions as the required transceiver for the bi-directional data transmission between a computer and an electronic device with a specific interface of USB 2.0. The value of an emitter resistor within an emitter resistance network in the conventional ECL circuit is adjusted till its output voltage amplitude meets the USB 2.0 specification. A number of voltage level shifting and capacitive coupling circuits are added to both the input and output sections of the conventional ECL circuit making it directly interfaceable with the popular CMOS logic family. A collector electrode switch network is also added to the conventional ECL circuit to make its output terminals tri-statable thus compatible with the communication scheme of half duplexing under the USB 2.0 specification.