Power supply noise in a 22nm z13™ microprocessor
Successful power supply noise mitigation requires a system-level approach that includes design and modeling of the mitigation circuits with the power delivery network (PDN) on the chip, the chip module, the backplane, and the voltage regulator module (VRM). Traditionally, periodic square-wave activity patterns with all cores in sync, which yield low-frequency (LF) or mid-frequency (MF) impedance peaks associated with the backplane and chip/module, respectively, are considered to give rise to the worst case power supply noise. However, voltage droops that are both deeper and faster at a single victim core are created when cores change activity in more complicated patterns, termed as perfect storms in this work. These patterns excite high-frequency (HF) modes that are not stimulated when all cores switch simultaneously, and require an accurate model of the packaged chip, including effective core-to-core inductances due to currents traveling between cores through low-resistance module planes.