Power-Supply Noise Reduction Using Active Inductors in Mixed-Signal Systems

Power-supply noise is a significant problem in mixed-signal systems on a chip. This is due to the impulse like current drawn by digital CMOS gates which couples to the sensitive analog circuits through supplies and the substrate. A noise-localization technique using on-chip active inductors is proposed. This would make the noise current generated by the digital gates to remain local in the region of the digital gates. This active inductor is designed to have minimum overhead in terms of voltage headroom and area. Simulations of benchmark digital gates, frequency dividers, and buffers demonstrate about 30-dB reduction of noise with this technique. Measured results from a test-chip carrying this design further demonstrate the functionality of this inductor.