Overview of vectorless/early power grid verification

The power distribution network of an integrated circuit must be checked throughout the design process to ensure that supply voltage fluctuations do not exceed certain critical thresholds. One way of doing this is by simulation, which requires knowledge of the circuit currents that load the grid. These currents are hard to specify. In many cases, and certainly during early power grid design, they may be simply unknown because the circuit itself may not yet be specified. Vector-less verification refers to the class of techniques, developed over the last 12 years, for verifying the grid in the absence of complete information about the circuit currents.