Memory device, memory system including memory device, and operating method of memory device

A memory system comprising:

• a plurality of memory devices;
• and
• a memory controller configured to control the plurality of memory devices,
• wherein each of the plurality of memory devices is configured to:
• perform a first-type ZQ calibration in response to a command received from the memory controller;
• and
• perform a second-type ZQ calibration without the command being received the memory controller,
• wherein each of the plurality of memory devices comprises drivers configured to transmit data signals to the memory controller, and
• wherein each of the first-type ZQ calibration and the second-type ZQ calibration is configured to calibrate the drivers of each of the plurality of memory devices.

An operating method of a memory device, the operating method comprising:

• receiving, at the memory device, a command from an external memory controller;
• performing, at the memory device, a first-type ZQ calibration in response to the command;
• and
• performing, at the memory device, a second-type ZQ calibration in response to an internally managed count reaching a threshold value and without receiving the command from the external memory controller,
• wherein the first-type ZQ calibration and the second-type ZQ calibration are performed to calibrate drivers of the memory device, and the drivers are configured to transmit data signals to the external memory controller.