Automatic calibration circuits for operational calibration of critical-path time delays in adaptive clock distribution systems, and related methods and systems

Automatic calibration circuits for operational calibration of critical-path time delays in adaptive clock distribution systems, and related methods and systems, are disclosed. The adaptive clock distribution system includes a tunable-length delay circuit to delay distribution of a clock signal provided to a clocked circuit, to prevent timing margin degradation of the clocked circuit after a voltage droop occurs in a power supply supplying power to the clocked circuit. The adaptive clock distribution system also includes a dynamic variation monitor to reduce frequency of the delayed clock signal provided to the clocked circuit in response to the voltage droop in the power supply, so that the clocked circuit is not clocked beyond its performance limits during a voltage droop. An automatic calibration circuit is provided in the adaptive clock distribution system to calibrate the dynamic variation monitor during operation based on operational conditions and environmental conditions of the clocked circuit.