Semiconductor memory device having on die thermal sensor

A method for measuring an internal temperature of a semiconductor memory device, the method comprising:

• generating a plurality of flag signals by measuring an internal temperature of a semiconductor memory device, the voltage level of each of the plurality of flag signals corresponding to the measured internal temperature;
• providing a self-refresh period corresponding to the measured internal temperature in response to the plurality of flag signals;
• and
• determining a measuring period of the internal temperature of the semiconductor memory device in response to the plurality of flag signals and a temperature sensing enable signal,
• wherein the determining of the measuring period of the internal temperature includes:
• generating an initial period signal and a plurality of additional period signals, each of the additional period signals having a different period, in response to the temperature sensing enable signal;
• and
• selecting, for determining the measuring period, one of the initial period signal and the plurality of additional period signals in response to the plurality of flag signals.

A semiconductor memory device, comprising:

• a temperature information output unit configured to detect an internal temperature of the semiconductor memory device and to generate a plurality of flag signals;
• a self-refresh oscillation unit configured to provide a self-refresh period in response to the plurality of flag signals outputted from the temperature information output unit;
• a period signal generating unit configured to output an initial period signal and a plurality of additional period signals each having a different period in response to a temperature sensing enable signal inputted from an external;
• and
• a period signal selection unit configured to select, for determining a measuring period of the temperature information output unit, one of the initial period signal and the plurality of additional period signals in response to the plurality of flag signals.