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Method for outputting internal temperature data in semiconductor memory device and circuit of outputting internal temperature data therebyMethod for outputting internal temperature data in semiconductor memory device and circuit of outputting internal temperature data thereby description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070109013, Method for outputting internal temperature data in semiconductor memory device and circuit of outputting internal temperature data thereby. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/335,036, filed 18 Jan. 2006, which claims priority from Korean Patent Application No. 10-2005-0005277, filed Jan. 20, 2005, the contents of which are hereby incorporated by reference in their entirety. BACKGROUND OF THE INVENTION [0002] 1. Technical Field [0003] The present invention relates to temperature sensing to be applied in a semiconductor memory device, and more particularly, to a method for outputting internal temperature data in a volatile semiconductor memory device such as Dynamic Random Access Memory (DRAM) and a circuit for outputting the internal temperature data thereby. [0004] 2. Discussion of Related Art [0005] Generally, for high-efficiency electronic systems such as personal computers or electronic communication machinery, volatile semiconductor memory devices such as DRAM onboard as memory have become faster and more highly integrated. In case of semiconductor memory devices onboard in battery-operated systems such as mobile phones or laptop computers, the low power consumption characteristics are critically required. Therefore, semiconductor manufacturers have continuously worked to reduce the operating current and standby current in order to provide a mobile oriented low power solution. [0006] The data retention characteristics of the memory cell in the DRAM comprising one transistor and one storage capacitor are very sensitive to temperature. Thus, if the memory cell can be controlled suitably according to its temperature characteristics, this can be useful in saving power. An approach to realize such power saving by installing a temperature sensor in the semiconductor memory device such as the DRAM and differentiating a refresh cycle according to the temperature of a chip is well known in this art. [0007] FIG. 1 illustrates a circuit 100 of a temperature sensor to be installed in a semiconductor memory device. The temperature sensor is a semiconductor temperature sensor of a band gap reference type basically comprising a current mirror-type differential amplifier and a diode, which is well known in this art. Currents flowing in branches C and A of the temperature sensor have temperature-current characteristics as shown in FIG. 2. In FIG. 2, the horizontal axis indicates temperature and the vertical axis indicates current. The characteristic graphs of the branches C and A intersect at trip point TI. [0008] However, the temperature sensor as described above is very sensitive to a noise environment, and thus the deviation of the temperature data as output according to the operation modes of the semiconductor memory device may be great. Consequently, there are problems in that accuracy of the obtained temperature data is lowered and reliability of the temperature data is also lowered accordingly. [0009] In practice, an attempt has been made to transfer the temperature of the DRAM chip into a chip-set such as a CPU or memory controller so that the chip-set controls various operations of the DRAM, for example, a refreshing operation. In such a case, the temperature sensor is continuously or periodically activated to perform a temperature sensing operation. When an external command is applied like a waveform (Command) in FIG. 3 while the temperature sensor is periodically operating, internal temperature data is read-out in the DRAM until a transition of a waveform (TS-RD) occurs. FIG. 3 illustrates temperature data output timing according to the conventional art. [0010] When the internal temperature data of the DRAM chip is obtained by the manner shown in FIG. 3, the temperature data obtained according to various operation modes of the DRAM may have differences. That is, if the external command is applied when the DRAM performs an operation of reading the data, it is difficult for the temperature sensor to sense the present temperature data in a sufficiently stable state, and it may output deviated temperature data due to the noise environment. Consequently, the reliability of the internal temperature data as obtained is lowered, and power consumption is increased since the temperature sensor is in the continuously or periodically operating state. Moreover, since an output access time of the temperature data is indicated as access section TA of FIG. 3, there is a problem in that the time for the chip-set to obtain the temperature data becomes somewhat long. [0011] In order to obtain accurate temperature data, it is preferable to ensure that the environment is without any noise, during which the temperature sensor can perform the temperature sensing operation in a sufficiently stable state, for more than the time for responding to the sensing of the temperature sensor. Thus, measures to make it possible to obtain more reliable temperature data within a shorter time, without damaging/interrupting the performance of the semiconductor memory device, are required in the battery-operated systems. SUMMARY OF THE INVENTION [0012] Therefore, the present invention is directed to provide a semiconductor memory device to solve the aforementioned conventional problems. [0013] One aspect of the present invention is a method for outputting internal temperature data in a semiconductor memory device which can provide a temperature sensor onboard in the semiconductor memory device with a stable operation environment, and a circuit for outputting the internal temperature data thereby. [0014] Another aspect of the present invention is a method for outputting internal temperature data in a semiconductor memory device which can reliably obtain temperature data of a chip, without continuously or periodically operating a temperature sensor. [0015] Another aspect of the present invention is a method for outputting internal temperature data in a semiconductor memory device which can output relatively accurate temperature data at high speed, without continuously or periodically operating a temperature sensor, and a circuit for outputting the internal temperature data thereby. [0016] Another aspect of the present invention is a method for outputting temperature data so as to obtain more reliable temperature data within a shorter time, minimizing or reducing power consumed in a temperature sensor onboard in the DRAM. [0017] In accordance with exemplary embodiments of some of the aforementioned aspects, a method for outputting internal temperature data comprises externally outputting the internal temperature data stored in a register during a preceding driving cycle in response to a temperature data request signal; driving a temperature sensor during a predefined time section after the output of the internal temperature data is completed, and storing, in the register, the internal temperature data obtained from the temperature sensor. [0018] Preferably, the temperature data request signal may be an expansion mode register set (EMRS) command as provided in an external memory controller connected to the semiconductor memory device, and the temperature sensor may be a semiconductor temperature sensor of a band gap reference type. [0019] Further, it may be suitable that the predefined time section is below about 5 microseconds, and the internal temperature data can be output by a data output buffer which is in an inactive state in a preceding data access operation mode. [0020] According to the method for outputting the temperature data, power consumption can be reduced and relatively accurate temperature data can be externally output within a shorter time. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Method for outputting internal temperature data in semiconductor memory device and circuit of outputting internal temperature data thereby... 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