Low voltage/low power temperature sensor

Information

  • Patent Grant
  • 6421626
  • Patent Number
    6,421,626
  • Date Filed
    Friday, November 6, 1998
    26 years ago
  • Date Issued
    Tuesday, July 16, 2002
    22 years ago
Abstract
The present invention is a temperature sensor which is based on the actual temperature coefficients of a device in the circuit, rather than a predetermined threshold voltage that varies across different devices. This temperature sensor includes a circuit which determines the temperature of a device. More particularly, CMOS circuit is provided which uses a current source to generate charge and discharge voltages applied to a capacitor. These voltages are dependent on the temperature coefficient of a resistor in the current source. The charge and discharge times are then used to determine a frequency which is dependent on the temperature coefficient of the resistor. Thus, the temperature is sensed based on the output frequency of the circuit. Additionally, the present invention includes a mechanism which allows the temperature sensor to be activated or deactivated as needed.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a circuit which determines the temperature of a device. More particularly, a complementary metal oxide semiconductor (CMOS) circuit is provided which uses a current source to generate charge and discharge voltages applied to a capacitor. These voltages are dependent on the temperature coefficient of a resistor in the current source. The charge and discharge times are then used to determine a frequency which is dependent on the temperature of the resistor. Thus, the temperature is sensed based on the output frequency of the circuit.




2. Description of Related Art




In the computer and data processing industry there is an ever increasing demand for higher processing speeds and systems which are capable of performing multiple tasks in parallel. Often times there are tradeoffs associated with this increased processing performance. One example is an increased level of power consumption and corresponding increase in the amount of heat generated by a particular device or IC.




Temperature sensors have many applications. A large number of circuits and/or functional units in today's electronic devices are temperature sensitive and require accurate and reliable temperature information in order to take corrective action when the temperature becomes too high. For example, the system frequency may be reduced when a certain temperature threshold is reached in order to cause the temperature to be reduced below the critical point. Further, systems, such as portable electronic devices (games, laptops, notebook computers, personal digital assistants), and the like are sensitive to power consumption and may need to shut down all or part of their operations when the power, which is function of temperature, reaches a certain level. Additionally, some individual circuits may need to be disconnected or shut down when the temperature reaches a predetermined level. Another application is an oscillator, such as a crystal oscillator which is frequency dependent. In this case a temperature sensor is required to adjust the accuracy of the output frequency. Rechargeable battery applications is yet another area wherein an accurate and reliable temperature sensor will have utility.




Conventional temperature sensing techniques are typically based on a predetermined value of a transistor threshold voltage. In reality the integrated circuit (IC) fabrication process is not exactly consistent between groups of wafers, or lots. Thus, a threshold voltage for transistors in a particular lot of wafers will not be the same as the threshold voltage for the transistors in another lot. Thus, the correlation between the frequency and the temperature will not be consistent between sensors fabricated in different lots. The functional units relying on the temperature to perform various data processing activities may operate at different temperatures resulting in inconsistent results across the same device fabricated in a different lot.




Therefore, it can be seen that a need exists for a temperature sensor that provides greater consistency when manufactured at different times and in different lots in order to provide a temperature dependent output signal having increased accuracy.




SUMMARY OF THE INVENTION




In contrast to the prior art, the present invention is a temperature sensor which is based on the actual temperature coefficients of a device in the circuit, rather than a predetermined threshold voltage that varies across different devices.




Broadly, the present invention relates to a circuit which determines the temperature of a device. More particularly, CMOS circuit is provided which uses a current source to generate charge and discharge voltages applied to a capacitor. These voltages are dependent on the temperature coefficient of a resistor in the current source. The charge and discharge times are then used to determine a frequency which is dependent on the temperature of the resistor. Thus, the temperature is sensed based on the output frequency of the circuit.




An additional feature of the present invention is a mechanism which allows the temperature sensor to be activated or deactivated as needed.




Therefore, in accordance with the previous summary, objects, features and advantages of the present invention will become apparent to one skilled in the art from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a block diagram of a data processing system including components capable of implementing the present invention;





FIG. 2

is a schematic diagram of the elements that make up a preferred embodiment of the present invention;





FIG. 3

is a more detailed schematic diagram of the activation mechanism of the present invention; and





FIG. 4

are timing diagrams showing the waveforms at particular times which are present at various nodes in the circuit schematic of FIG.


2


.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




In order for the various data processing systems to utilize the functions of the present invention, the temperature sensor is provided in selected ones of the integrated circuits, or chips, that make up the system. For example, the temperature sensor of the present invention may be provided on an application specific integrated circuit (ASIC) in the clocking portion. In this manner, the frequency output from the clock circuit can be lowered when the sensor of the present invention determines that a temperature above a predetermined threshold has been reached. Thus, control signals can be provided to the clock circuit, such as a phase locked loop (PLL) in order to regulate the temperature of the chip. This clock circuit may be used to drive the frequency of a microprocessor, microcontroller, digital signal processor (DSP) or like embedded on the ASIC. In another application, the sensor of the present invention can determine when a temperature threshold is reached in order to turn off various non-critical portions of an IC to reduce the power consumption and corresponding temperature. Those skilled in the art will be familiar with numerous other uses of the temperature sensor of the present invention.




Referring to

FIG. 1

, a typical data processing system is shown which may be used in conjunction with the present invention. This data processing system could include virtually any system having a need to regulate the temperature of an included device or circuit, including a laptop computer, PDA, desktop computer, or the like. A central processing unit (CPU)


10


such as the Pentium II microprocessor, commercially available from Intel Corp. may be provided, although other microprocessors from other manufacturers, such as the PowerPC microprocessor, commercially available from IBM Corporation may also be used. Microprocessor


10


is interconnected to the various other components by system bus


12


read only memory (ROM)


16


is connected to CPU


10


via bus


12


and includes the basic input/output system (BIOS) that controls the basic computer functions. Random access memory (RAM)


14


, I/O adapter


18


and communications adapter


34


are also interconnected to system bus


12


. I/O adapter


18


may be a small computer system interface (SCSI) adapter that communicates with a disk storage device


20


. Communications adapter


34


interconnects bus


12


with an outside network enabling the data processing to communication with other such systems, via the internet, local area network (LAN), or the like. Input/output devices are also connected to system bus


12


via user interface adapter


22


and display adapter


36


. Keyboard


24


, track ball


32


, mouse


26


and speaker


28


are all interconnected to bus


12


via user interface adapter


22


. Display monitor


38


is connected to system bus


12


by display adapter


36


. In this manner, a user is capable of inputting to the system through the keyboards


24


, trackball


32


, or mouse


26


and receiving output from the system via speaker


28


and display


38


. Additionally, an operating system, such as one of the versions of Windows, commercially available from Microsoft Corporation is used to coordinate the functions of the various components shown in FIG.


1


.




Referring to

FIG. 2

, a preferred embodiment of the temperature sensor of the present invention is shown. In this embodiment a switching mechanism is shown with allows the temperature sensor to be turned on or off. In some instances it is advantageous to have the ability to control whether or not the temperature sensor is operating. For example, when a data processing system is in a low power or “sleep” mode it is not necessary for the temperature sensor to be operational, since during “sleep” mode most functions of the system are turned off and the temperature will be at an acceptable level.




More particularly, a switching circuit is shown which can be used by the system microprocessor or controller to disable the temperature sensor in order to further reduce the total power consumption. An input signal is provided on node


50


to a first inverter


51


. Additionally, a second inverter


53


, delay circuit


55


and third inverter


57


are also part of the switching circuit. A P-type transistor


58


is shown with its gates connected to the output of inverter


51


. P-type devices will conduct electricity when a logical “0” (absence of a voltage) is provided to their gate. An N-type transistor


52


having its gate connected to the output of inverter


53


. N-type transistors will conduct electricity when a logical “1” (voltage) is applied to their gate. P-type transistor


54


is also shown with its gate connected to the output of delay circuit


55


, and it can be seen N-type transistor


56


has its gate connected to the output of inverter


57


.




When a “stop” signal input to node


50


is set equal to logical


1


, then the current source formed by transistors


101


,


102


,


103


,


104


and resistor


105


is turned off. Specifically, when the output of inverter


51


transitions from a “1” to a “0” transistor


58


will conduct electricity and pull node


60


to Vcc. The output of inverter


53


will be a “1” when the input to node


50


is set. Therefore, transistor


52


will conduct electricity and pull node


61


down to the reference voltage (potential), in this case, Vss. It can be seen that when node


60


is at Vcc, transistors


101


and


102


will not conduct and cannot supply the current needed for the temperature sensor to operate. Transistor


106


,


107


,


108


and


109


are P-type transistors and form current mirrors. Each of these transistors has its gate connected to node


60


such that when transistors


101


and


102


of the current source are off they will also be turned off.




When it is desired for the system to turn on the temperature sensor the input control signal at node


50


is switched from high (1) to low (0). This causes a short pulse to be generated at the gate of transistor


54


(from delay circuit


55


). Also a pulse is provided from inverter


57


to the gate of transistor


56


. When transistor


54


conducts, node


61


will then be pulled up to Vcc causing transistors


103


and


104


of the current source to conduct. Similarly, node


60


is pulled down to Vss when transistor


56


begins to conduct and transistor


101


and


102


also begin to conduct and the current source then operates.




Next, the operation of the temperature sensor will be described, also in conjunction with FIG.


2


. As noted above, transistors


101


,


102


,


103


,


104


and resistor


105


form a current source which provides electrical current through transistors


102


,


104


and resistor


105


. All of the transistors,


101


,


102


,


103


and


104


are working at weak inversion.




The voltage (Va) at node


62


can be determined using the following equation:








Va=kT/q


ln


S




104




S




101




/S




103




S




102


.  (1)






Where k is Boltzmann's constant, q is electron charge and T is temperature in degrees Kelvin. This constant (kT/q) is about 26 millivolts at 300 degrees K. In equation (1), “S” represents the transistor size, i.e. width/length (W/L), for the transistors in the current source (


101


,


102


,


103


,


104


). A current mirror is formed by transistor


106


wherein the same current that flows through transistors


102


,


104


and resistor


105


will also flow through transistor


106


and resistors


109


and


110


.




The voltage (Vd) at node


63


can be determined in accordance with the following equation:








Vd


=(


S




106




/S




102


)(


R




110




/R




105


)(


Va


).  (2)






And the voltage (Vc) at node


64


can be determined by the following:








Vc


=(


S




106




/S




102


)((


R




109




+R




110


)


/R




105


)(


Va


).  (3)






Vc is the voltage drop across resistors


109


and resistor


110


, and Vd is the voltage across resistor


110


.




In a preferred embodiment of the present invention, the capacitors are implemented by using N-type depletion transistors. That is, the source and drain of an N-type transistor are coupled to one another and a capacitance is created across the gate and the connected source/drain of the transistor. Capacitors


120


,


121


and


122


are such N-depletion transistors. The temperature sensor of the present invention then utilizes capacitor


120


to determine the output frequency. More particularly, when the current source is active, transistor


108


will be turned on to conduct electricity. When N-type transistor


115


is on, the current will be used to charge capacitor


120


. P-type transistor


107


will also conduct when transistor


108


is turned on. This will cause transistors


111


and


112


to conduct such that capacitor


120


has a path to Vss for the discharge current. The current used to charge capacitor


120


is represented by the following equation:








Ic


=(


S




108




/S




102


)(


Va/R




105


).  (4)






The discharge current from capacitor


120


can be characterized by:








Id


=(


S




112




/S




111


)(


S




107




/S




102


)(


Va/R




105


).  (5)






The voltages Vc and Vd, as noted above, are the charging and discharging voltages, respectively.




The voltage at node


71


is switched between Vc and Vd through two N-type transistor passgates


146


and


147


. When passgate


146


is turned on, the voltage on node


71


is at Vc (charge). Also, when transistor


146


is turned on N-type passgate transistor


115


will also be turned on allowing capacitor


120


to be charged to the Vc voltage level through node


70


. While the voltage at node


70


is greater than the voltage at node


71


, the voltage at node


72


is approximately the same as the threshold voltage (Vtn) of an N-type transistor, e.g. transistor


130


and the voltage at node


73


is substantially zero (0). At the next transition, node


75


goes high (1) and turns on passgate


147


and N-type pass gate, transistor


117


. In this case, the voltage at node


71


then switches to the Vd (discharge) level. When passgate


117


turns on, node


70


begins to discharge to the Vd voltage level and the discharge current will flow through transistor


112


to Vss.




In a preferred embodiment of the present invention a comparator is used to as a current to frequency converter. More particularly the comparator will transform the analog current output sensor signal to a digital control signal. The comparator is formed by P-type transistors


109


,


125


and


126


, along with N-type transistors


127


,


128


,


129


and


130


, where transistors


128


and


129


are provided, in a preferred embodiment, to add more gain to transistors


127


and


130


. As shown in more detail by

FIG. 4

, the waveforms at nodes


72


and


73


are quasi square waves with a 180 degree phase shift. The frequency of these square waves carry the temperature information. This frequency can be translated into a digital number by counting the square wave pulses over a predetermined period.




A differential to single converter (level shifter) is then utilized in a preferred embodiment of the present invention to translate the differential waveforms into a single temperature dependent signal. This converter is formed by P-type transistors


133


and


134


in conjunction with N-type transistors


132


and


135


. From

FIG. 4

, it can be seen that when node


73


is at the threshold voltage of an N-type transistor (Vtn), node


72


will be low and vice versa. During the time period when node


72


is at the Vtn level, transistor


132


will be turned on causing the gates of transistors


133


and


134


to be pulled to Vcc−Vtp. That is, the gates of these transistors is pulled to the voltage level of the input voltage (Vcc) minus the threshold voltage of a P-type transistor (Vtp). This, in turn causes node


74


to be pulled up to voltage Vcc. Node


74


is effectively the output of the temperature sensor of the present invention. However, this node is connected to a series of inverters which are used to increase the speed of the signal on node


74


. In a preferred embodiment four (4) inverters are connected. These inverters are formed by P-type transistors


136


,


138


,


140


and


142


, connected with N-type transistors,


137


,


139


,


141


and


143


, respectively. Thus, when node


72


is at the Vtn level, node


74


will also be high and the output of the temperature sensor at node


145


will also be high. During this same time period, node


73


will is low and will not turn on transistor


135


. However, during the next time period, node


73


will be at the Vtn voltage level turning on transistor


135


which causes node


74


to be pulled down to Vss thereby turning on P-type transistor


136


, This causes the output of the inverter (formed by transistors


136


and


137


) to be high (1). In this case the output of the temperature sensor at node


145


will be low (0). Thus, when node


73


is high, the output at node


145


will be low.




In this manner the temperature sensor of the present invention will provide an output signal at node


145


having a frequency that is dependent on the temperature of various components in the circuit. The frequency at the output will be based on two time periods, i.e. the time to charge the capacitor


120


and the time it takes to discharge the capacitor. The time to charge the capacitor is shown by the following equation:








t




c


=(


C




120


)(


Vcd


)/


Ic;


  (6)






where








Vcd=Vc−Vd


=(


S




106




/S




102


)(


R




109




/R




105


)(


Va


).  (7)






The time period for the sensor to discharge is determined by the following:








t




d


=(


C




120


)(


Vcd


)/


Id.


  (8)






The frequency at the output is shown by:






Frequency=1/(


t




c




+t




d


).  (9)






Then, substituting equations (4), (5), (6), (7) and (8) into equation (9), the following equation is generated:






Frequency=[(


S




108




/S




102


)(


S




112




/S




111


)(


S




107




/S




102)]/[(




C




120


)(


S




106




/S




102


)(


R




109


)][(


S




108




/S




102


)+(


S




112




/S




111


)(


S




107




/S




102


)].  (10)






Therefore, it can be seen in equation (10) that R


109


is the only temperature dependent element. Since the temperature coefficient of this resistance (TCR) is known, the frequency output will be inversely proportional to the TCR. By monitoring the frequency the temperature of the circuit can be determined. That is, as the frequency changes the chip temperature is sensed. Those skilled in the art will understand that a device, such as a counter, or the like can be connected to the output node


145


to monitor the frequency of the output signals, i.e. the number of times capacitor


120


charges and discharges over a given time period. For materials with a positive TCR, as the temperature increases, the frequency will decrease. Similarly, as the temperature decreases the frequency will correspondingly increase. Thus, the frequency is inversely proportional to the temperature of the sensing circuit, i.e. the thermal coefficient of the resistance for resistor R


109


. Once the frequency is sensed it can be determined if the temperature is above a predetermined threshold level. If so, then corrective action can be taken to shut off various functions in the device, turn off the entire device, or the like. When the frequency decreases to correspond to a temperature below the predetermined threshold, these functions can be turned back on. Of course, more than one predetermined threshold level is contemplated by the present invention wherein each level may correspond to different functions on the device.




One advantage of the temperature sensor of the present invention is that the frequency will be substantially supply voltage independent. Further, the present invention is transistor model independent. More particularly, the temperature sensor of the present invention is not dependent on the threshold voltage of the transistors, it is threshold voltage (Vt) independent. Equation (10) depends entirely on the actual characteristics of the circuit components, rather than a predetermined threshold voltage value for the N-type and P-type devices in the circuit.




The present invention will function at very low voltages since the current source includes only a single P-type transistor


101


and


102


. Therefore, the current can be provided by applying only the threshold voltage (Vtp) across these transistors, plus an additional small amount of voltage (on the order of a few hundred millivolts). It can be seen that the amount of power consumed by the present invention will also be relatively low based on the small amount of voltage needed for the temperature sensor circuit to operate. That is, the power is directly proportional to the voltage (P=VA).




In another preferred embodiment of the present invention, a constant frequency oscillator can be provided. This oscillator will also be a low power, low voltage system in accordance with the previous discussion and the description of the switching circuit of FIG.


3


. By properly choosing the resistor R


109


, such as an N-type resistor, to have a zero (0) temperature coefficient of resistance at a particular ambient temperature, the frequency output of the circuit will be constant. Thus, an accurate frequency level can be maintained. Those skilled in the art will understand that it may be necessary, for example, to alter the TCR for a corresponding temperature, such as by laser trimming or the like, in order to obtain a reference frequency at room temperature.




Referring to

FIG. 3

, a more detailed schematic of the switching circuit of the present invention is shown and will be described in conjunction with FIG.


2


. Inverters


51


and


53


are shown connected to pulse generator


55


which includes a delay circuit. This delay circuit includes five (5) additional inverters,


300


,


301


,


302


,


303


and


304


connected in series. The input to pulse generator circuit


55


is also connected as one input to a NOR gate


305


with the output of the series of inverters from inverter


304


being the other input to NOR gate


305


. As shown in

FIG. 2

, the output of pulse generator circuit


55


is provided to inverter


57


.




More particularly, when a logical zero (0) is input at node


50


, inverter


51


outputs a logical one (1) to transistor


58


of FIG.


2


and inputs a one to inverter


53


which outputs a zero to transistor


52


and to pulse generator circuit


55


. In this case a zero is input to NOR gate


305


at node A, while a one is output from inverter


304


and input to NOR gate


305


at node B. Those skilled in the art will understand that a time delay occurs for the binary input to inverter


300


to be processed by each inverter


300


,


301


,


302


,


303


,


304


and then output to NOR gate


305


as a logical one. In this manner, when a zero is input to node


50


, a zero is also input to inverter


300


and node A of NOR gate


305


. Delay inverters


300


,


301


,


302


,


303


and


304


will then cause a one to be input at node B of NOR gate


305


. At this time, a zero will be output from NOR gate


305


and a one will be output to P-type transistor


54


with a zero output to N-type transistor


56


. During this period, none of transistors


52


,


54


,


56


or


58


are turned on. When a logical one (1) is input at node


50


, a one is output to transistors


52


(on) and


54


and a zero is output to transistors


56


and


58


, i.e. transistors


54


and


56


will not be turned on, while transistors


52


and


58


will be on to keep the sensor off. Specifically, a one input to NOR gate


305


on node A and a zero input to NOR gate


305


on node B causes a zero to be output to inverter


306


. This in turn causes a one to be input to P-type transistor


54


(off) and inverter


57


. The output of inverter


57


is a zero which is then input to N-type transistor


56


(off).




When it is desired to turn on the temperature sensor of the present invention, the input at node


50


transitions back to a logical zero, which places a zero on node A of NOR gate


305


at the same time the previous logical zero is still on node B of NOR gate


305


. Therefore, during the delay time required for the logical one (due to the logical zero now input to node


50


) to traverse the delay inverters (


300


,


301


,


302


,


303


,


304


) a zero, zero (0, 0) will be present on nodes A and B of NOR gate


305


. During this time a logical one output pulse is generated from NOR gate


305


. This pulse will have a duration substantially equivalent to the amount of time required for the zero input to inverter


300


to traverse the delay inverters. The output pulse from NOR gate


305


will then cause the temperature sensor of the present invention to begin operating. That is, a logical one is output from NOR gate


305


thus causing a logical zero to be provided from inverter


306


to P-type transistor


54


, which turns this transistor on. Additionally, a one is output from inverter


57


that will cause N-type transistor


56


to being to conduct. As noted previously, transistor


54


will input Vcc to the gate of transistors


103


,


104


and transistor


56


will pull the gate of transistors


101


,


102


to Vss causing it to be turned on. The current source of the temperature sensor will then begin operation. Subsequent to the duration of the output pulse from generator


55


, the switching mechanism will remain off until the input to node


50


is changed to logical zero when transistors


52


and


58


are turned off and the current generator ceases operation until a transition to a logical one occurs at node


50


and a pulse is subsequently generated from NOR gate


305


by changing the input to node


50


to a zero.




The switching operation of the temperature sensor in accordance with these output signals has been described above in conjunction with FIG.


2


. Thus, a control circuit can be used to provide the input signals to node


50


that will cause the temperature sensor of the present invention to be shut off in order to conserve electrical power.





FIG. 4

is a timing diagram showing the waveforms present at various ones of the nodes in the temperature sensor circuit of FIG.


2


. It can be seen that the first waveform, present and node


70


, is substantially a sawtooth wave that represents capacitor


120


during its charging state (upward slope) during the time when the voltage charging voltage Vc is present on node


71


and then discharging (downward slope) when the discharge voltage Vd is present on node


71


. The waveform on node


70


is based upon the frequency of the capacitor and the temperature coefficient of resistor R


2


. This signal will then be transformed into a digital signal such that the frequency can be monitored, and therefore, the current sensed by basically counting the signal transitions at the output node


145


.




The second waveform shows the voltage on node


71


. It can be seen that the charge voltage Vc corresponds to the charging of capacitor


120


which occurs when transistor


146


of the pass gate is turned on. Voltage Vd corresponding to the discharge of capacitor


120


and occurs when transistor


147


of the pass gate is turned on.




The third waveform shows the voltage on node


72


which is an output of the differential comparator circuit formed by transistors


125


,


126


,


127


,


128


,


129


and


130


. The fourth waveform represents the voltage on node


73


which is another output of the comparator circuit. It can be seen from

FIG. 4

that the output signals at nodes


72


and


73


are


180


degrees out of phase with one another. These signals are then input to a differential to single converter circuit formed by transistors


132


,


133


,


134


and


135


. Node


74


is the output of this converter circuit and provides an output signal to four (4) inverters.




The fifth waveform is the temperature sensor circuit output. It can be seen that it follows the waveform at node


72


. More particularly, when node


72


is at Vtn, transistor


132


is turned on and causes reference potential to be input to the gate of N-type transistor


134


which places a logical one on node


74


. This will cause a logical one to be output on node


145


(an even number of inverters is present between nodes


74


and


145


). When node


73


is at Vtn, N-type transistor


135


is turned on causing a reference potential (logical 0) to be output on node


74


and ultimately on node


145


. Thus, it can be seen that the output on node


145


follows the waveform on node


72


, but is the complement of the waveform on node


73


.




Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the appended claims.



Claims
  • 1. A temperature sensor, comprising:a current source having a plurality of transistors and coupled to at least one resistor, said current source driving a current through said resistor; and means for converting said current from said current source and said resistor to a temperature dependent frequency signal, wherein the temperature dependence of said frequency signal derives from temperature characteristics of said at least one resistor and is independent of a threshold voltage of any of said plurality of transistors.
  • 2. A sensor according to claim 1 wherein said temperature dependent frequency signal is based upon a thermal coefficient of resistance of said at least one resistor.
  • 3. A sensor according to claim 2 wherein a frequency of said temperature dependent frequency signal is proportional to a temperature of said at least one resistor.
  • 4. A sensor according to claim 1 wherein said means for converting comprises:a capacitor coupled to temperature dependent charge and discharge voltages at opposite terminals of said at least one resistor; a comparator for receiving an input signal from said capacitor and for outputting differential phase shifted control signals based thereon; and a circuit for combining said differential phase shifted control signals and for outputting said temperature dependent frequency signal.
  • 5. A sensor according to claim 4 further comprising means for monitoring said temperature dependent frequency signal, and for regulating the operation of other circuits based upon a predetermined temperature level.
  • 6. A sensor according to claim 5 further comprising means for deactivating said temperature sensor based upon an external control signal.
  • 7. A sensor according to claim 1 wherein said temperature dependent frequency signal is independent of a supply voltage for said current source.
  • 8. A sensor according to claim 1 further comprising:a current mirror coupled between said current source and said at least one resistor, said current mirror driving a current equal to an output current of said current source through said at least one resistor; and at least one capacitor coupled to said at least one resistor, wherein charge and discharge times for said at least one capacitor, which are dependent upon a voltage across said at least one resistor, are employed to generate said temperature dependent frequency signal.
  • 9. A sensor according to claim 8 further comprising:a level shifter coupled between said at least one resistor and said at least one capacitor, said level shifter converting a differential voltage across said resistor to a single temperature dependent signal forming said temperature dependent frequency signal; and an inverter coupled to said level shifter.
  • 10. A sensor according to claim 8 wherein said a frequency of temperature dependent frequency signal is proportional to both a capacitance of said at least one capacitor and a resistance of said at least one resistor.
  • 11. A sensor according to claim 8 further comprising:a comparator coupled to said at least one capacitor and converting a current from charge or discharge of said at least one capacitor to a frequency signal.
  • 12. A sensor according to claim 8 further comprising:a switching mechanism switching a terminal of said at least one capacitor between a charge voltage at one terminal of said at least one resistor and a discharge voltage at an opposite terminal of said at least one resistor.
  • 13. A sensor according to claim 1 wherein a resistance of said at least one resistor is an only temperature dependent variable affecting a frequency of said temperature dependent frequency signal.
  • 14. A method of sensing a temperature in an integrated circuit device, comprising the steps of:providing a current from a current source driving at least one resistor included in said integrated circuit device, said current source having a plurality of transistors and coupled to said at least one resistor; and converting said current from said current source to a temperature dependent frequency signal, wherein the temperature dependence of said frequency signal derives from temperature characteristics of said at least one resistor and is independent of a threshold voltage of any of said plurality of transistors.
  • 15. A method according to claim 14 wherein said temperature dependent frequency signal is based upon a thermal coefficient of resistance of said at least one resistor.
  • 16. A method according to claim 15 wherein a frequency of said temperature dependent frequency signal is proportional to a temperature of said at least one resistor.
  • 17. A method according to claim 16 wherein said steps of converting comprises the steps of:providing a capacitor coupled to temperature dependent charge and discharge voltages at opposite terminals of said at least one resistor; receiving, by a comparator, an input signal from said capacitor and outputting, by said comparator, differential phase shifted control signals based thereon; and combining said differential phase shifted control signals and outputting said temperature dependent frequency signal.
  • 18. A method according to claim 17 further comprising the steps of:monitoring said temperature dependent frequency signal; and regulating the operation of other circuits based upon a predetermined temperature level.
  • 19. A method according to claim 18 further comprising the step of deactivating said temperature sensor based upon an external control signal.
  • 20. A data processing system having a mechanism for regulating the power consumption of components included in said data processing system, comprising:at least one integrated circuit device that performs a portion of data processing functions in said data processing system; a temperature sensor having a current source having a plurality of transistors and coupled to at least one resistor, said sensor including means for converting a current from said current source and driven through said at least one resistor to a temperature dependent frequency signal, wherein temperature dependence of said frequency signal derives from temperature characteristics of said at least one resistor and is independent of a threshold voltage across any of said plurality of transistors; and a monitor for determining when said temperature dependent frequency signal reaches a predetermined threshold and controlling operation of said at least one integrated circuit based thereon.
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Number Name Date Kind
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Entry
Vladimir Székely et al., “CMOS Sensors for On-Line Thermal Monitoring of VLSI Circuits”, IEEE Transactions on VLSI Systems, vol. 5, No. 3, pp. 270-276, Sep. 1997.*
V. Szekely, et al., “CMOS Sensors for On-Line Thermal Monitoring of VLSI Circuits”, IEEE Transactions on Very Large Scale Integration (VLSI) Systems, V. 5, No. 3, Sep. 1997, pp. 270-276.