Method of generating a multi-level signal using a selective level change, a method of transmitting data using the same, and a transmitter and memory system performing the same

A memory device comprising:

• a data input/output (I/O) buffer including a plurality of transmitters connected to a plurality of data I/O pads, respectively, each of the plurality of transmitters configured to generate a multi-level signal having one of three or more voltage levels that are different from each other by performing a first voltage setting operation in which a first voltage interval and a second voltage interval are adjusted and performing a second voltage setting operation in which a voltage swing width is adjusted, the first voltage interval representing a difference between a first pair of adjacent voltage levels among the three or more voltage levels, the second voltage interval representing a difference between a second pair of adjacent voltage levels among the three or more voltage levels, the voltage swing width representing a difference between a lowest voltage level and a highest voltage level among the three or more voltage levels,
• wherein, in an initial operation, a first code is provided for a first transmitter to generate a first multi-level signal output through a first data I/O pad, the first code is provided for a second transmitter to generate a second multi-level signal output through a second data I/O pad, and the first voltage interval, the second voltage interval and the voltage swing width of the first multi-level signal are equal to the first voltage interval, the second voltage interval and the voltage swing width of the second multi-level signal, and
• wherein, in a training operation, a second code different from the first code is provided for the first transmitter to generate the first multi-level signal by performing the first voltage setting operation and the second voltage setting operation, a third code different from the first and second codes is provided for the second transmitter to generate the second multi-level signal by performing the first voltage setting operation and the second voltage setting operation, the first voltage interval and the second voltage interval of the first multi-level signal are different from the first voltage interval and the second voltage interval of the second multi-level signal, and the voltage swing width of the first multi-level signal are equal to the voltage swing width of the second multi-level signal.

A system comprising:

• a memory controller;
• a memory device connected to the memory controller;
• and
• a plurality of transmitters connected to a plurality of data input/output (I/O) pads, respectively, each of the plurality of transmitters configured to generate a multi-level signal having one of three or more voltage levels that are different from each other by performing a first voltage setting operation in which a first voltage interval and a second voltage interval are adjusted and performing a second voltage setting operation in which a voltage swing width is adjusted, the first voltage interval representing a difference between a first pair of adjacent voltage levels among the three or more voltage levels, the second voltage interval representing a difference between a second pair of adjacent voltage levels among the three or more voltage levels, the voltage swing width representing a difference between a lowest voltage level and a highest voltage level among the three or more voltage levels,
• wherein, in an initial operation, a first code is provided for a first transmitter to generate a first multi-level signal output through a first data VO pad, the first code is provided for a second transmitter to generate a second multi-level signal output through a second data I/O pad, and the first voltage interval, the second voltage interval and the voltage swing width of the first multi-level signal are equal to the first voltage interval, the second voltage interval and the voltage swing width of the second multi-level signal, and
• wherein, in a training operation, a second code different from the first code is provided for the first transmitter to generate the first multi-level signal by performing the first voltage setting operation and the second voltage setting operation, a third code different from the first and second codes is provided for the second transmitter to generate the second multi-level signal by performing the first voltage setting operation and the second voltage setting operation, the first voltage interval and the second voltage interval of the first multi-level signal are different from the first voltage interval and the second voltage interval of the second multi-level signal, and the voltage swing width of the first multi-level signal are equal to the voltage swing width of the second multi-level signal.