US Patent 10381055 Flexible DLL (delay locked loop) calibration

A memory device performs DLL (delay locked loop) calibration in accordance with a DLL calibration mode configured for the memory device. A host controller can configure the calibration mode based on operating conditions for the memory device. The memory device includes an input/output (I/O) interface circuit and a delay locked loop (DLL) circuit coupled to control I/O timing of the I/O interface. A control circuit of the memory device selectively enables and disables DLL calibration in accordance with the DLL calibration mode. When selectively enabled, the DLL calibration is to operate at a time interval identified by the DLL calibration mode, and when selectively disabled, the DLL calibration is to cease or refrain from DLL calibration operations.