Circuit and method for isolating circuit blocks for reducing power

Abstract

An integrated circuit is divided into functional blocks. The integrated circuit includes current source based circuitry such as Emitter Coupled Logic (ECL), Current Mode Logic (CML), or Source Coupled Logic (SCL) Isolation blocks (14-20) are placed in signal paths to and from each functional block. A multiple output bias driver circuit (13) couples to each functional block. The multiple output bias driver circuit (13) provides a signal for enabling and disabling current sources of a functional block. A bias control logic circuit (12) controls the isolation blocks (14-20) and the multiple output bias driver (13). A functional block that is idle in the operation of the integrated circuit is shut down by the bias control logic circuit (12) to conserve power. The multiple output bias driver circuit (13) receives control signals from the bias control logic circuit (12) to turn off current sources in the idle functional block. Isolation blocks (14-20) receive control signals from the bias control logic circuit (12) to isolate the idle functional block and to provide a predetermined logic level in the signal paths from the idle functional to prevent propagation of an erroneous signal.