WO1999012010A1 - Capteur de limite de temperature integre - Google Patents

Capteur de limite de temperature integre Download PDF

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Publication number
WO1999012010A1
WO1999012010A1 PCT/US1998/014225 US9814225W WO9912010A1 WO 1999012010 A1 WO1999012010 A1 WO 1999012010A1 US 9814225 W US9814225 W US 9814225W WO 9912010 A1 WO9912010 A1 WO 9912010A1
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WO
WIPO (PCT)
Prior art keywords
temperature
voltage
junction
circuit
proportional
Prior art date
Application number
PCT/US1998/014225
Other languages
English (en)
Inventor
Sui Ping Shieh
Original Assignee
Maxim Integrated Products, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maxim Integrated Products, Inc. filed Critical Maxim Integrated Products, Inc.
Publication of WO1999012010A1 publication Critical patent/WO1999012010A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/01—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using semiconducting elements having PN junctions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K3/00—Thermometers giving results other than momentary value of temperature
    • G01K3/005—Circuits arrangements for indicating a predetermined temperature

Definitions

  • the present invention relates to the field of temperature limit sensors, monitors and switches.
  • the present invention is an integrated temperature limit sensor or monitor for providing a logic level change when the device becomes subjected to a excessively high (or excessively low) temperature, the output of which may be used for such purposes as alarm control, equipment control, shutdown, etc., depending on the application. Accordingly, the closest prior art is devices more commonly known as temperature switches which similarly provide an on-off, high-low or open- closed type of response.
  • Temperature switches of various kinds are well known in the prior art. Such switches are often used as an input to a temperature control, such as by way of example, in a home thermostat for heating and air conditioning controls, or heaters for coffee makers and the like. These switches typically are based on a simple bi-metal temperature sensing element, can handle substantial power, are of low cost for their power handling ability, and of adequate reliability for their usual applications. However, they are also relatively large, not very accurate or repeatable, and typically would not have the reliability of integrated circuits. In other applications, temperature switches are merely used to monitor equipment, such as for shutting down the equipment if it begins to overheat, or in some cases preventing the turning on of the equipment if its temperature is too low for the proper operation thereof.
  • overheating of the equipment may be indicative of such things as the failure of an active cooling system, inadequate ventilation for a passive cooling system, or an excessively high ambient temperature.
  • sensing the temperature of the equipment has certain advantages in that not all cooling system degradations result in overheating, and not all overheating is a result of cooling system degradations or failures.
  • sensing the attainment of a temperature limit of operation of a system and shutting the same down, or preventing the starting thereof should prevent a temperature induced costly failure of the equipment, irrespective of the cause of the extraordinary equipment temperature condition.
  • Sensing equipment temperature may also be advantageous, however, in conjunction with other cooling system sensors, such as fan operation sensors, etc., as such other sensors may provide a warning of another condition which will naturally lead to an excessive temperature condition, and can also be of diagnostic value.
  • a simple integrated temperature monitor operative independent of the cause of the extraordinary condition, provides a simple overriding indication of the extraordinary condition without concern for its cause, to allow action to be taken, such as a programmed shut down of the system to avoid damage thereto .
  • FIG. 1 One prior art integrated circuit temperature limit monitor is shown in Figure 1.
  • a bandgap generator generates a current proportional to absolute temperature through resistor R6, which is mirrored to transistor Ql as part of the bandgap generator circuit and is also mirrored to transistors Q3 and Q4.
  • the current mirrored to transistor Q3 passes through resistor R7 , giving a voltage across resistor R7 which is also proportional to absolute temperature.
  • resistor R7 As long as that voltage is below the VBE of transistor Q7 , transistor Q7 will be off. Consequently, the output of the circuit will be pulled high by the current flowing through resistor R4 and Q4 (which normally will actually be less than the full current mirrored thereto because of the high collector voltage on transistor Q4 when transistor Q7 is off) .
  • the circuit of Figure 1 may be trimmed at a given temperature, such as at room temperature, to have a trip point at a substantially different temperature, either higher or lower than room temperature, by forcing the voltage of node Nl at room temperature to determine, at room temperature, the trip point voltage of node Nl . From this, the anticipated trip point at the desired trip temperature may be determined from the trip point voltage measured at room temperature and the anticipated change in the VBE of transistor Q7 between room temperature and the desired trip temperature. Then, resistor R7 may be trimmed so that the voltage of node Nl at room temperature is equal to the anticipated trip voltage at the desired trip temperature times the absolute room temperature divided by the absolute temperature at the desired trip point.
  • the setting of the trip point at room temperature for the prior art devices can yield substantial variation and inaccuracy in the actual trip point when the desired trip point is substantially above or substantially below room temperature because of the unknown division of the current between resistor R7 and the base emitter junction of the transistor at the trip point.
  • This is to be compared with the present invention wherein the effect of the beta of transistor Q7 on the performance of the circuit is eliminated, as is the requirement to force the voltage on any node, thereby making the setting, at room temperature, of the desired trip point an easier and more accurate process .
  • Integrated temperature limit sensors which may be used as stand alone devices or as part of a larger integrated circuit to provide a logic signal change upon a temperature rise to a predetermined level, or alternatively, upon a temperature drop to a predetermined level.
  • the temperature limit sensor generates a voltage proportional to absolute temperature and compares that voltage with a voltage proportional to the voltage across a forward biased pn junction, or a base-emitter voltage of a transistor.
  • the combination of the increasing voltage proportional to absolute temperature and the decreasing pn junction voltage with absolute temperature provides enhanced sensitivity and reliable and repeatable performance. Alternate embodiments are disclosed.
  • Figure 1 is a circuit diagram of a prior art temperature limit sensor.
  • Figure 2 is a circuit diagram of a preferred embodiment of the present invention.
  • Figure 3 is a circuit diagram of an alternate embodiment of the present invention.
  • Figure 4 is a circuit diagram of a further alternate embodiment of the present invention.
  • Figure 5 is a plot illustrating the variation in the voltages V R and V D with temperature and the associated trip points.
  • transistor Q6 is eight times as large as transistor Q5.
  • transistors Ql and Q2 are of the same size, and for convenience may be the same size as transistor Q5.
  • transistors Q3 , Q4 and Q7 may also be of the same size as transistor Q5.
  • transistor Q2 will mirror the current there through to transistor Ql . Consequently, the current through transistors Q5 and Q6 will be equal, though of course transistor Q6, having an area eight times as large as transistor Q5, will have a current density of only one-eighth of that of transistor Q5. Accordingly, the VBE of transistor Q6 will be less than the VBE of transistor Q5 , the difference appearing as a voltage drop across resistor R6.
  • the current through resistor R6 is proportional to absolute temperature (PTAT) .
  • This current sets the voltage at the bases of transistors Ql, Q2 , Q3 and Q4 equal to the voltage drop across resistor R2 and the VBE Q 2 of transistor Q2.
  • resistor R3 is equal to resistor R2 and transistor Q3 is the same size as transistor Q2
  • the current through resistors R5 and R6 (assuming transistor Ml is off) , or R5 alone (assuming transistor Ml is on) , will also be proportional to absolute temperature.
  • the voltage on the negative input V R to comparator COMP is a voltage proportional to absolute temperature.
  • the voltage on the base of transistor Q4, and particularly the value of resistor R4, will also determine the current through resistor R4, transistor Q4 and diode connected transistor Q7. If transistor Q4 is the same size as transistor Q2 and resistor R4 is the same resistance as resistor R2 , the current through diode connected transistor Q7 will also be proportional to absolute temperature. This is not a requirement, however, as other types of current biasing for the diode connected transistor Q7 may be used if desired. Of particular importance, however, is that diode connected transistor Q7 be biased into forward conduction from some current source so that the positive input V D to the comparator is responsive to the VBE of transistor Q7.
  • resistor R4 and transistor Q4 could be used for resistor R4 and transistor Q4 , or alternatively, transistor Q4 could be eliminated and a resistor such as resistor R4 of appropriate size connected directly to the common base collector connection of transistor Q7 to provide similar results , as shown in Figure 3.
  • the biasing of diode connected transistor Q7 by the current proportional to absolute temperature does have certain advantages . Because currents and voltages proportional to absolute temperature are already generated as part of the circuit, a forward conduction current through diode connected transistor Q7 proportional to absolute temperature is easily provided. Further, it will be noted from the foregoing equations that the current proportional to absolute temperature is generated by transistors Q5 and Q6 and resistor R6 , together with the biasing thereof, so as to provide a current proportional to absolute temperature which naturally is independent of the supply voltage (provided the supply voltage has adequate headroom for operation of the circuit over the ' temperature range) .
  • use of the current proportional to absolute temperature for the forward conduction biasing of diode connected transistor Q7 has the further advantage of essentially providing a regulated bias current, that is, a bias current which is substantially input voltage (V REG ) independent, allowing operation of the circuit over a wider supply voltage range, if the application so requires, without substantial error in the preset temperature limit setting.
  • diode connected transistor Q7 in essence simply a pn junction, may be replaced by other types of pn junctions, such as by way of example, by a simple diode Dl as shown in Figure 4.
  • the characteristics of a simple pn junction or a diode connected transistor are substantially the same, the forward conduction voltage drop of the pn junction varying with temperature in accordance with the variation of VBE with temperature given by the foregoing equations.
  • a voltage proportional to the voltage drop across as forward conducting pn junction such as a divided down VBE, or a series of two or more pn junction voltage drops may be used if desired.
  • resistor R7 provides hysteresis for the trip point of the comparator, resistor R7 normally being relatively small in comparison to resistor R5 , though as a minimum preferably being adequate to provide enough hysteresis to avoid oscillation of the circuit in the presence of noise from neighboring circuitry and other equipment.
  • the hysteresis need only represent a very few degrees Fahrenheit to be adequate under most conditions .
  • the output of the comparator would be considered a positive logic signal in that the limit condition would be indicated by the normally low signal going high. If, on the other hand, the parameters for the various elements of the circuit are chosen to provide a limit signal when the temperature is excessively high, then the embodiments of Figures 2 through 4 would, in effect, provide a negative logic signal, being normally high when the temperature was below the limit and going low when the temperature limit is reached. These, of course, may easily be reversed as desired, by reversing the inputs to the comparator and substituting a p-channel transistor for n-channel transistor Ml to preserve the small amount of positive feedback for hysteresis purposes.
  • resistor R4 by design, intentionally has a somewhat lower resistance than its final expected value, with a view toward laser trimming of resistor R5 (increasing the resistance thereof) to adjust the trip point at the time of wafer sort. Having the resistance of resistor R5 lower than ultimately desired decreases the voltage V R on the negative input to the comparator at any given temperature .
  • the voltage V R before trim versus temperature in degrees Kelvin is as shown in Figure 5.
  • the value of the resistor R5 is increased until the desired trip point is reached.
  • a characteristic of a current proportional to absolute temperature as generated by a bandgap generator is very well known and very repeatable, as is the forward conduction voltage drop across a pn junction.
  • V R in relation to V D at some other known temperature.
  • trimming to adjust the trip point at room temperature as described could be done by trimming resistors other than R5 , but trimming of resistor R5 is preferred because its adjustment does not effect the balance of the bandgap generator or current mirrors and it is easier to trim than R6.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
  • Semiconductor Integrated Circuits (AREA)

Abstract

L'invention concerne un capteur de limite de température intégré, susceptible d'être utilisé comme dispositif autonome ou dans un circuit intégré de plus grande taille, qui fournit un changement de signal logique lorsque la température s'élève jusqu'à un niveau préétabli ou, inversement, lorsque la température s'abaisse à un niveau préétabli. Ce capteur engendre une tension proportionnelle à la température absolue et compare ladite tension avec une tension proportionnelle à la tension aux bornes d'une jonction PN à polarisation directe, ou à la tension base-émetteur d'un transistor. La combinaison de la tension qui augmente proportionnellement par rapport à la température absolue et de la tension de la jonction PN qui diminue proportionnellement par rapport à la température absolue confère au capteur considéré une sensibilité accrue ainsi qu'une fiabilité et une fidélité de fonctionnement.
PCT/US1998/014225 1997-09-03 1998-07-09 Capteur de limite de temperature integre WO1999012010A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US92292297A 1997-09-03 1997-09-03
US08/922,922 1997-09-03

Publications (1)

Publication Number Publication Date
WO1999012010A1 true WO1999012010A1 (fr) 1999-03-11

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PCT/US1998/014225 WO1999012010A1 (fr) 1997-09-03 1998-07-09 Capteur de limite de temperature integre

Country Status (2)

Country Link
TW (1) TW379481B (fr)
WO (1) WO1999012010A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6806772B2 (en) 2002-11-06 2004-10-19 Itt Manufacturing Enterprises, Inc. Power transistor array temperature control system
FR2857456A1 (fr) * 2003-07-07 2005-01-14 St Microelectronics Sa Cellule de detection de temperature et procede de determination du seuil de detection d'une telle cellule

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61118630A (ja) * 1984-11-15 1986-06-05 Mitsubishi Electric Corp Ｉｃチツプ温度検出装置
FR2627027A1 (fr) * 1988-02-04 1989-08-11 Sgs Thomson Microelectronics Detecteur de surcharge thermique dans un circuit integre
US5359236A (en) * 1993-05-25 1994-10-25 Harris Corporation Integrated circuit thermal sensor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61118630A (ja) * 1984-11-15 1986-06-05 Mitsubishi Electric Corp Ｉｃチツプ温度検出装置
FR2627027A1 (fr) * 1988-02-04 1989-08-11 Sgs Thomson Microelectronics Detecteur de surcharge thermique dans un circuit integre
US5359236A (en) * 1993-05-25 1994-10-25 Harris Corporation Integrated circuit thermal sensor

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
G.C. MEIJER: "A LOW-POWER EASY-TO-CALIBRATE TEMPERATURE TRANSDUCER", IEEE JOURNAL OF SOLID-STATE CIRCUITS., vol. 17, no. 3, June 1982 (1982-06-01), NEW YORK US, pages 609 - 613, XP002078237 *
PATENT ABSTRACTS OF JAPAN vol. 010, no. 305 (P - 507) 17 October 1986 (1986-10-17) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6806772B2 (en) 2002-11-06 2004-10-19 Itt Manufacturing Enterprises, Inc. Power transistor array temperature control system
FR2857456A1 (fr) * 2003-07-07 2005-01-14 St Microelectronics Sa Cellule de detection de temperature et procede de determination du seuil de detection d'une telle cellule
US7003424B2 (en) 2003-07-07 2006-02-21 Stmicroelectronics Sa Temperature detection cell, and method to determine the detection threshold of such a cell

Also Published As

Publication number Publication date
TW379481B (en) 2000-01-11

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