ECL/CML pseudo-rail circuits, cutoff driver circuit, and latch circuit.

摘要

A pseudo-rail circuit is coupled between the differential output gate or buffer of an emitter coupled logic or current mode logic (ECL/CML) circuit and the high potential level power rail. The pseudo-rail circuit provides a pseudo-rail node (A). A first clamp circuit is coupled to the pseudo-rail node for clamping the pseudo-rail node at a first potential level (GND) in response to a first control signal. A second clamp circuit is coupled to the pseudo-rail node for clamping at a second potential level in response to a second control signal. A clamp switching circuit alternately applies the first and second clamp circuits to the pseudo-rail node in response to the control signals. As a cutoff driver circuit, the first clamp circuit of the pseudo-rail circuit applies the high potential level of the power rail to the pseudo-rail node. The second clamp circuit pulls down the pseudo-rail node to hold the output of the differential output gate in the cutoff state. An output enable (OE) differential gate or buffer provides the clamp switching circuit. The pseudo-rail circuit is incorporated directly in a latch circuit to initiate the cutoff state in response to an OE cutoff signal without losing latched data and without requiring an additional output buffer stage.