Chip-Package Resonance in Core Power Supply Structures for a High Power Microprocessor

摘要

Advanced microprocessors have high current demands at low voltage and require low impedance power across a broad frequency range. Silicon circuits want to look out from their power terminals and see a power supply impedance that is less than or equal to a target impedance. Decoupling capacitance on the chip and package inductance form a parallel RLC circuit that has a high impedance at the chip-package resonant frequency. Circuits on the chip are not able to get the power that they need at this resonant frequency. The RLC parameters have been experimentally measured for a 70 watt microprocessor and an equivalent circuit has been developed. Chip capacitance is a strong function of bias voltage. SPICE simulation of the equivalent circuit reveals the extent of the chip-package resonance issues. The power supply impedance is determined in the resonant frequency band. Time domain simulations show the maximum excursions expected for the power supply voltage onboard the microprocessor chip.