TECHNICAL FIELD 0001 The invention relates generally to thermal sensing and, more particularly, to calibrating a thermal sensor in an integrated circuit.

BACKGROUND 0002 Transistors can be used as logical switches in an integrated circuit (IC). Transistors generate heat when switching from an off state to an on state, or from an on state to an off state, within the IC. If this heat is neither properly dissipated nor otherwise accounted or compensated, the transistor can experience degeneration leading to transistor failure. 0003 However, although the IC can have an associated temperature sensor to detect excessive heat, there can be significant variation in the readings obtained from the temperature sensor from IC to IC. Therefore, a calibration of the temperature sensor is performed to compensate for this variation. Conventionally, one method of calibration is to generate a temperature in the IC chip environment and then calibrate the temperature sensor or temperature sensors at that temperature. In other words, determine what the readings of the temperatures sensors are at a given temperature, and use this as a basis for comparison when determining an unknown temperature. However, calibration of temperature sensors can be time intensive and costly. 0004 Therefore, what is needed is a way to calibrate an IC chip that solves at least some of the disadvantages associated with conventional calibration of IC chips.

SUMMARY OF THE INVENTION 0005 The present invention provides an integrated circuit. A temperature sensitive ring oscillator (TSRO) is provided. A temperature measuring device is proximate the TSRO. A memory is employable for storing data that is a function of the output of the TSRO and the temperature measuring device.

BRIEF DESCRIPTION OF THE DRAWINGS 0006 For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying drawings, in which: 0007 FIG. 1 schematically depicts an integrated circuit comprising a plurality of TSROs and a temperature measuring device; and 0008 FIG. 2 illustrates a method for calibrating a TSRO.

DETAILED DESCRIPTION 0009 In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without such specific details. In other instances, well-known elements have been illustrated in schematic or block diagram form in order not to obscure the present invention in unnecessary detail. Additionally, for the most part, details concerning network communications, electromagnetic signaling techniques, and the like, have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the understanding of persons of ordinary skill in the relevant art. 0010 It is further noted that, unless indicated otherwise, all functions described herein may be performed in either hardware or software, or some combination thereof. In a preferred embodiment, however, the functions are performed by a processor, such as a computer or an electronic data processor, in accordance with code, such as computer program code, software, and/or integrated circuits that are coded to perform such functions, unless indicated otherwise. 0011 Turning to FIG. 1, disclosed is an IC calibration system 100. The system 100 has an integrated circuit (IC) 110. The IC 110 has a plurality of temperature sensitive ring oscillators (TSRO) 120. Generally, a ring oscillator consists of a number of gain stages in a feedback loop. With the correct configuration, phase shift, and so on, the output of a ring oscillator oscillates at a certain frequency, determined by the ring oscillator components. A TSRO further employs a temperature sensitive element to affect the characteristics of the oscillation, such as number of oscillation cycles per second. Coupled to a TSRO there can be a TSRO counter logic. Generally, a TSRO counter logic measures the number of oscillations of a TSRO and forwards that information as appropriate. Furthermore, the TSRO counter logic controls aspects of TSRO functionality. In FIG. 1, a TSRO counter logic 123 monitors and controls a TSRO logic 121, and indicia of the numbers of oscillations measured by the TSRO logic counter 123 is forwarded to a calibrator 150. 0012 The IC 110 further comprises input/output (I/O) devices 130. The I/O devices 130 are generally employed to transfer data on and off the IC 110. The thermal resistor 137 is proximate to at least one TSRO 120, which is illustrated as TSRO 121. However, the thermal resistor 137 has its own input and output ports. 0013 The system 100 further comprises a current source 135. The current source is typically not part of the IC 110, Instead, it is part of a tester 147. Generally, the tester 147 determines calibration values for the TSRO 121 and is not integral to each IC 110, but is employable with a plurality of IC 110s. In one embodiment, a constant electrical current from the current source 135 can be routed through an I/O device 130 through the thermal resistor 137. The voltage across the thermal resistor 137 is a function of both the current through the resistor and the resistance of the thermal resistor. The resistance of the thermal resistor is a function of the temperature of the thermal resistor. The TSRO 121 is proximate to the thermal resistor 137. Therefore, in one embodiment, the temperature of the thermal resistor 137 is substantially similar to the temperature of the TSRO 121. 0014 The system 100 further comprises a voltmeter 140 coupled in parallel to the thermal resistor 137. The voltmeter 140 is part of the tester 147. The voltmeter 140 measures the voltage across the thermal resistor 137. The voltage measured by the voltmeter 140 is generally proportional to the temperature of the thermal resistor 137. The TSRO 121, proximate to the thermal resistor 137, has substantially the same temperature, due to their close physical location to one another. 0015 In FIG. 1, the TSRO 121 oscillates at a certain frequency for a given temperature, and indicia of this oscillation frequency value is forwarded to the TSRO counter logic 123. From the TSRO counter logic 123, processed indicia of the frequency count is forwarded to a calibrator 150, part of the tester 147. In an alternative embodiment, an indicia of the oscillation value is forwarded to a memory 170 after being processed by the TSRO counter logic 123. In FIG. 1, indicia of the voltage of the thermal resistor 137 is also forwarded to the calibrator 150. The calibrator 150 employs a look-up table 160, part of the tester 147, to determine the equivalent temperature the thermal resistor 137. The look-up table 160 comprises thermal resistor 137 temperature values corresponding to various voltage values. The voltage values are read from the voltmeter 140, and hence, the temperature of the TSRO 121 is determined. 0016 The TSRO 121 calibration value is then conveyed to the memory 170. The calibration value comprises the determined temperature of the proximate thermal resistor 137. In a further embodiment, the calibration value also comprises the measured frequency of the TSRO 121 as well as the determined temperature of the proximate thermal resistor 137. By storing and employing the TSRO 121 calibration value, it is not necessary to wait until the temperature of the IC 110 is at a predetermined value. Instead, the temperature of the TSRO 121 of the IC 110 is determined, and the calibration of the TSRO 121 occurs at that temperature. In one embodiment, the IC 110 does not remain idle (that is, untested) for the period of time until the temperature of the IC 110 is even over the chip. 0017 In a further embodiment, at least one second TSROs 120 is calibrated with the same calibration value in the memory 170. Generally, the TSROs 120 and the TSRO 121 share similar calibration characteristics because they are fabricated within the same IC. Therefore, the TSROs 120 can employ the same calibration values. 0018 In a still further embodiment, a constant voltage source is employed, and the resulting current through the thermal resistor 137 is measured. The measurement of the current is employed by the calibrator 150 to determine the equivalent temperature of the thermal resistor 137. The frequency of the TSRO 121 is also measured, and both these values are stored in the calibration memory 170. 0019 Turning now to FIG. 2, disclosed is a method for employing the tester 147. In step 210, a known current is generated by the current source 135. In an alternative embodiment, a known voltage is generated by a voltage source. In step 220, the voltage that is generated across the thermal resistor 137 is measured by the voltmeter 140. In an alternative embodiment, the current that flows through the resistor 137 is measured by an ampere meter. In step 230, the frequency of oscillations of the TSRO are measured. In step 240, this indicia is processed by the TSRO counter logic 123, and the processed indicia is then forwarded to the calibrator 150. 0020 In step 250, the calibrator 150 employs the look-up table 160 to determine the corresponding temperature. The temperature and the oscillator frequency are both stored in the memory 170 for calibration of the TSRO 121. In step 260, the TSRO 121 oscillation value and the equivalent look-up table temperature are stored in the memory 170. In step 270, the calibration value stored for the TSRO 121 is also associated with the calibration values of the other TSROs 120. 0021 It is understood that the present invention can take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. The capabilities outlined herein allow for the possibility of a variety of programming models. This disclosure should not be read as preferring any particular programming model, but is instead directed to the underlying mechanisms on which these programming models can be built. 0022 Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.