An All-Digital, VMAX-Compliant, and Stable Distributed Charge Injection Scheme for Fast Mitigation of Voltage Droop

Distributed charge injection (CI) scheme featuring distributed VMAX-complaint CI clamps, distributed digital droop detectors (DDDs), and distributed droop controllers for fast mitigation of voltage droop is fabricated in 10-nm FinFET CMOS test-chip. A local DDD detects nearby voltage droop in two clock cycles of IP block, and quickly triggers associated CI clamps to inject charge from a high voltage rail (e.g., 1.8 V) to VCC for immediate voltage droop mitigation. Local droop controller collectively guarantees stable operation after CI is triggered, by gradually allowing the voltage regulator to take over after the droop subsides. Measured data shows droop reduction by up to 45% for a uniform transient load current transition, and by 38% in a hot-spot load current transition at 1.0 V and 2.0 GHz. The droop reduction is translated to power savings of ∼11% over a guard-banded baseline.