Feedforward active substrate noise cancelling technique using power supply di/dt detector

This paper demonstrates a feedforward active substrate noise cancelling technique using a power supply di/dt detector. Since the substrate is tied to the ground line, the substrate noise is closely related to the ground bounce which is caused by di/dt when inductance is dominant on the ground line impedance. The active cancelling technique detects the di/dt of the power supply current and injects an anti-phase signal into the substrate so that the di/dt proportional substrate noise is cancelled out. 34% of the substrate noise reduction was achieved in a test circuit for the first trial. It is theoretically shown that the optimized canceller design will enhance the suppression ratio up to 56%.