Investigating Crosstalk in Sub-Threshold Circuits

Mini Nanua1 and David Blaauw2
1Sun Microsystems Inc., 2University of Michigan


Ultra-low power designs are increasingly exploiting the subthreshold region of operation of CMOS circuits. In order to ensure correct functionality in a design, it is necessary to guarantee signal integrity. We evaluate crosstalk in an industrial microprocessor core designed in 65nm Bulk CMOS technology as the operating voltage is reduced from nominal to subthreshold. We partition the problem into categories dictated by crosstalk analysis: crosstalk induction, crosstalk propagation and failure criterion (noise rejection curve of msff). We develop testbench circuits to study these analysis components individually. We also selected 2500 noise sensitive interconnects from the industrial microprocessor design and simulated them for crosstalk with varying operating voltages. We observe that although crosstalk injection increases in sub-threshold operation, the propagation does not, resulting in overall less crosstalk sensitive design.