A Charge-Injection-Based Active-Decoupling Technique for Inductive-Supply-Noise Suppression

We demonstrate an active circuit to detect and suppress excessive supply-voltage undershoots and overshoots caused by large current transients or by excitation of supply resonance. A nominal-voltage active supply, V_DDA, is used to inject extra charge into the power grid during excessive undershoots. The use of a nominal-voltage V_DDA eliminates the need for any high-voltage supplies and enables use of decaps and transistors with nominal oxide thickness. Furthermore, this method has the advantage that the active decap bank, C_alpha, behaves as a passive decap when the supply voltage is within safety margins.