Apparatus for reducing power supply noise in an integrated circuit

Abstract

A main power supply continuously provides a current to a power input terminal of an integrated circuit device under test (DUT). The DUT's demand for current at the power input terminal temporarily increases during state changes in synchronous logic circuits implemented within the DUT. To limit variation (noise) in voltage at the power input terminal arising from these temporary increases in current demand, a charged capacitor is connected to the power input terminal during each DUT state change. The capacitor discharges into the power input terminal to supply additional current to meet the DUT's increased demand. Following each DUT state change the capacitor is disconnected from the power input terminal and charged to a level sufficient to meet a predicted increase in current demand during a next DUT state change.

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