Enhancing the Tolerance to Power-Supply Instability in Digital Circuits

As IC technology scales down, power supply instability may dramatically contribute to signal integrity loss. In this paper, the authors propose a new methodology to enhance circuit tolerance to power-supply voltage (V_DD1) local variations, without degrading its performance. The underlying idea is to add additional tolerance to the edge trigger of the clock signal driving specific memory cells. The clock duty-cycle (CDC) is thus dynamically modulated according to V_DD. Two architectures are presented, and one of them is shown to be effective. The key module is a clock stretching logic (CSL) block, used to increase CDC according to V_DD-V_SS variations. Moreover, when clock frequency reduction is inevitable, circuit tolerance when disturbances start to occur is enhanced, allowing the clock generator to react and reduce its frequency. Experimental results based on SPICE simulations for simple combinational, pipeline and finite-state machine (FSM) circuits are used to demonstrate the usefulness of the proposed methodology.