A 16 nm All-Digital Auto-Calibrating Adaptive Clock Distribution for Supply Voltage Droop Tolerance Across a Wide Operating Range

A 16 nm all-digital auto-calibrating adaptive clock distribution (ACD) enhances processor core performance and energy efficiency by mitigating the adverse effects of high-frequency supply voltage (V-DD) droops. The ACD integrates a tunable-length delay prior to the global clock distribution to prolong the clock-data delay compensation in core paths for multiple cycles after a droop occurs to provide a sufficient response time for clock frequency (F-CLK) adaptation. A dynamic variation monitor (DVM) detects the onset of the droop and interfaces with an adaptive control unit and clock divider to reduce F-CLK in half at the TLD output to avoid path timing-margin failures. An auto-calibration circuit enables in-field, low-latency tuning of the DVM to accurately detect V-DD droops across a wide range of operating conditions. The auto-calibration circuit maximizes the V-DD-droop tolerance of the ACD while eliminating the overhead from tester calibration. From 109 die measurements across a wafer, the auto-calibrating ACD recovers a minimum of 90% of the throughput loss due to a 10% V-DD droop in a conventional design for 100% of the dies. ACD measurements demonstrate simultaneous throughput gains and energy reductions ranging from 13% and 5% at 0.9 V to 30% and 13% at 0.6 V, respectively.