8.7 Dual-use low-drop-out regulator/power gate with linear and on-off conduction modes for microprocessor on-die supply voltages in 14nm

In recent generations of microprocessors, there has been an increase in the number and types of processors integrated on the same die. For example, in [1] several IA (Intel architecture) cores have been integrated on-chip with a graphics processor. Multi-core trends are expected to increase in future generations with different cores and units requiring varying supply voltages. As platform footprints are also required to decrease, this causes a unique challenge for voltage regulation. In [2], an on-die switching fully integrated voltage regulator (FIVR) was demonstrated, which presents a very good solution in many cases. However, the FIVR requires inductors, which may not always be available. In addition, it may be desirable to sub-divide some of the FIVR domains using power gates and/or linear voltage regulators, such as low-drop-out regulators (LDO). LDOs can be used to enable different units of the chip to operate at their optimal voltage levels, which could save power. For example, different types of cores often have significantly different minimum-V_cc levels in low-power mode. In addition, a core or graphics unit could enter a high-performance mode, where the voltage is ramped up to enable performance, while other cores are in sleep or low-power modes.