MXPA00010016A - Method and apparatus for measuring temperature with an integrated circuit device - Google Patents

Abstract

A temperature-sensor is implemented with a temperature-sensitive component (Q1) of an IC chip which functions as a radio frequency (RF) transponder (200) capable of measuring parameters associated with an object and transmitting data to an external reader/interrogator (106, 400). In use with a pneumatic tire (104), the transponder measures temperature and pressure within the tire. The transponder includes circuitry (226) for controlling windows of time (WT and WP) during which real-time temperature and pressure measurements are made, and for storing (236) calibration data, transponder ID number and the like, and for transmitting this information in a data stream (Figure 3C) to the reader/interrogator. An excessive temperature condition may also be sensed (MTMS 218) and included in the data stream. The circuitry of the transponder is preferably implemented on a single IC chip (204), using CMOS technology, with few components external to the IC chip. The transponder is preferably passive, deriving its operating power from an RF signal provided by the external reader/interrogator. Data (NT) indicative of temperature and data (NP) indicative of pressure are both transmitted to the reader/interrogator, along with calibration data. A calibration data stored by the transponder and transmitted in the data stream is a slope of NT/NP, or the"ratioed"response of the temperature count divided by the pressure count, which is determined during calibration of the transponder.

Description

METHOD AND APPARATUS FOR MEASURING TEMPERATURE WITH AN INTEGRATED CIRCUIT DEVICE TECHNICAL FIELD OF THE INVENTION The present invention relates to temperature measurements and more particularly to measuring temperature with a device that is incorporated in a chip or integrated circuit wafer (IC = Integrated Circuit) having additional functionality (i.e. temperature). BACKGROUND OF THE INVENTION A first type of temperature sensing device is capable of outputting a status signal indicative of whether a detected temperature is above or below a predetermined threshold temperature. A domestic thermostat is exemplary of threshold detection device. A second type of temperature sensing device is capable of detecting temperature across a range of temperatures, and outputting a signal that varies in magnitude in proportion to the measured temperature. An electronic clinical thermometer is exemplary of this temperature detection device. The present invention is directed to the type of temperature sensing device that is capable of outputting a signal that varies in magnitude in proportion to a detected temperature, this device is referred to below as a "temperature measurement" device. The present invention is further directed to detect temperature with a temperature measuring device that is implemented in an integrated circuit (IC) chip, the chip IC has intended functionality different from the temperature measurement. The patent of the U.S.A. No. 5,039,878 (08/77), fully incorporated by reference herein, describes a temperature sensing device. A semiconductor junction device (DI) integrated in an integrated circuit chip (IC) is used to generate a first signal (VI) that has a known variation with temperature. A second signal (V2) is generated by passing a current (I) that is proportional to the absolute temperature through a resistor (Rl), and also has a known variation with temperature that is opposite in sign to that of the first signal (SAW) . The two signals are compared to generate an output signal, which depends on whether the temperature of the flake is below or above a predetermined threshold temperature. In this implementation of a temperature detection circuit, the junction device (DI) is released accidentally and the temperature detection function (see column 1, lines 55-56).

The patent of the U.S.A. No. 5,039,878 mentioned above is representative of a temperature detection application, where it is desired to detect the temperature of an operating IC flake, it being generally well known that the heat generated (dissipated) by the operation of electronic components, is a source of consideration and difficulty in many electronic systems, especially those operating in closed spaces, without ventilation, as well as those in miniaturized high performance systems. The mechanisms of heat generation in electronic systems are well known and understood. In essence, any process (for example, an operational electronic system) that consumes energy generates heat. In the case of an electronic circuit, the circuit components become hot, which in turn stings anything in contact with them, including the surrounding air. Other applications of the prior art for temperature sensing devices include: control or stabilization of the operating temperature of circuit elements, the accuracy of which is affected either by changes in ambient temperature or changes in temperature caused by current flow in the circuit element itself; and control a power supply to other circuit elements (other than detection of temperature) to prevent its decomposition due to excessive temperature rise (overheating). Reference is made to the following U.S. Patents, each of which is fully incorporated herein: 3,703,651; 4,044,371; 4,854,731; 4,952,865; 4,970,497; 5,063,307; 5,213,416; 5,396,120; ,639,163; and 5,686,858. As mentioned above, the present invention is directed to a method and apparatus for measuring temperature over a range of temperatures. Although it is preferably implemented in flake, the purpose is not to regulate the operation of the Cl flake itself, but rather to verify the ambient temperature in the vicinity of the Cl flake such as the temperature inside a tire. A method and apparatus for detecting ambient temperature with a transponder associated with the tire is discussed in the main part below. Transponder or transceiver type identification systems are well known and in general are capable of receiving an incoming interrogation signal and responding to it by generating and transmitting an output response signal. The output response signal is in turn modulated or otherwise encoded in order to uniquely identify or label the particular object to which the transponder element is attached. An example of this system of identification of transponder type, is described in the patent of the US. No. 4,857,893, granted on August 15, 1989 to Carroll and fully incorporated herein. This patent describes a transponder device that receives a carrier signal from a server unit. This carrier signal, of frequency F, is rectified by a rectifier circuit in order to generate operational power. Alternately, adding a hybrid battery allows the device to become a self-powered beacon device. Logical / synchronization circuits are derived to a clock signal and second carrier signal of frequency F / n from the received carrier signal. A unique identification data word is stored in a Programmed Read Only Memory (PROM = Programmable Read-Only Memory). The data word is encoded and mixed with the carrier signal in a balanced modulator circuit, the output of which is transmitted to the master unit where it is decoded and used as an identification signal. All electrical circuits of the transponder device are achieved in the same monolithic semiconductor flake, which can be implemented as a Complementary Metal Oxide Semiconductor (CMOS = Complementary Metal Oxide Semiconductor) device. In the manufacture of tires, it is convenient to uniquely identify each tire as soon as as possible during the course of its manufacture. This is usually done by assigning an identification number (ID) to each tire. The ability to uniquely identify tires through their manufacture is particularly valuable in quality control so that the source of manufacturing problems can be easily assessed. For example, statistical process control and other methods can be used with tire identification to detect process parameters that leave the specification to detect machine wear, failure or poor fit. The identification information should be easily discernible throughout the manufacturing process, including through the post-manufacturing stages (eg inventory control). It is also beneficial to uniquely identify a tire through its service life (use), for example for warranty determination, and tire retreading should not adversely affect the ability to identify the tire. It is also important that the identification of the tire is easily discernable when the tire is mounted on a steel or aluminum rim (as is the case) including when the rim is one of a pair of rims on a dual wheel structure (as is common with trailers tractors). Apart from being able to uniquely identify a tire at various stages in its service and manufacturing life, it is beneficial to be able to verify tire pressure when the tire is in use. As is known, proper tire inflation is important for proper tire performance, including road handling, wear and the like. The patent of the U.S.A. No. 4,578,992 issued April 1, 1986 to Galasko, et al. And fully incorporated herein, discloses a device for indicating tire pressure that includes a coil and a capacitor for pressure sensitive detection, which forms a passive oscillator circuit with a natural resonant frequency, which varies with the tire pressure due to changes caused to the capacitance capacitor value.

The circuit is energized by pulses supplied by a coil placed outside the tire and attached to the vehicle, and the natural frequency of the passive oscillatory circuit is detected. The natural frequency of the capacitor / coil circuit is indicative of the pressure in the pressure sensitive capacitor. The use of radio frequency transponders (RF), located either inside the tire or on a rim for the tire, in conjunction with electronic circuits for transmission of an RF signal carrying tire inflation data (pressure) is also well known. An example of an RF transponder suitable for installation in the carcass of a vehicle tire is described in U.S. Pat. No. 5,451,959 granted on September 19, 1995 to Schuermann and fully incorporated herein. This patent describes the transponder system comprising an interrogation unit for communicating with a plurality of responding units. The responder unit contains a parallel resonant circuit having a coil and a capacitor for receiving an RF interrogation pulse. Connected to the parallel resonant circuit is a capacitor that serves as an energy accumulator. A processor may be provided for receiving signals from a detector that respond to physical parameters in the environment of the response unit 12, for example at room temperature, ambient pressure or the like. The detector can, for example, be a detector sensitive to air pressure. In this case, the response unit can be installed in the carcass of a vehicle tire with the help of an interrogation unit contained in the vehicle, it is possible to continuously check the air pressure in the tire. Another example of a suitable RF transponder to be installed in the tire of a vehicle, is described in U.S. Pat. No. 5,581,023 issued December 3, 1996 to Handfield et al., And fully incorporated herein. This patent discloses a transponder and a receiver unit, preferably a transponder for each vehicle tire, and the transponder can be fully placed within the vehicle tire. The transponder includes a pressure sensor and may include various other sensors such as a temperature sensor. An Application Specific Specific Circuit (ASIC) modality of the transponder is described With reference to Figure 9 of the patent, the ASIC (300) includes an oscillator (322) controlled by external crystal (325), a constant current device (310) providing current flowing through an external variable resistance pressure sensor (327), a window comparator circuit (324) having a lower threshold for reporting pressure information established by external resistors (329 and 331) connected in a voltage divider arrangement and a higher threshold controlled by an external variable resistor (333). A number of three position jumper links (328) is used to program a unique transponder unit serial number during its manufacture. The ASIC (300) it is energized by external battery (318), and a transmission circuit (312) is external to ASIC (300). Another example of a suitable RF transponder to be installed in a vehicle tire is described in U.S. Pat. No. 5,661,651 granted on August 26, 1997 to Geschke, et al. And incorporated herein by reference. This patent describes a wireless system for verifying vehicle parameters such as tire pressure. RF signals transmitted from different tires can be distinguished based on the frequency of the transmitted signal. In order to detect the pressure inside a tire, systems for checking tire pressure use a pressure detector located inside the tire. Figure 2 of this patent shows the preferred structure for a parameter detector and transmitter circuit when used in checking the pressure inside a vehicle tire. A transmitter and parameter detector circuit (20) includes a pressure-to-voltage transducer (21) and a circuit for power supply, energized by battery (24). The need to check the tire pressure when the tire is in use is highlighted in the context of tires that "run flat" (operate without being inflated), tires that are capable ofused in a completely deflated condition. These tires that work without being inflated can incorporate reinforced side walls, mechanisms to secure the surface in contact with the tire floor with the rim and a non-pneumatic wheel (donut) inside the tire, to allow a driver to maintain control of the vehicle after a loss of catastrophic pressure, and evolve to the point where it is increasingly less noticeable to the driver that the tire has deflated. The broad purpose of using tires that function without being inflated is to allow a driver of a vehicle to continue driving with the flat tire for a limited distance (for example 80 kilometers (or 50 miles)) before taking the tire to repair, instead stop at the side of the road to repair the flat tire. Therefore, it is generally convenient to provide a pressure low warning system, internal to the vehicle to alert (for example by a lamp on the dashboard or a buzzer) to the driver of air loss in a tire. These warning systems are known and do not form part of the present invention, per se.

Although the use of tire pressure transducers, in association with electronic circuits to transmit pressure data, is generally well known, These pressure data systems for tires have been plagued by difficulties inherent in the tire environment. These difficulties include effectively and reliably coupling RF signals inside and outside the tire, the rough use of the tire and electronic components to which they are subjected, as well as the possibility of harmful effects on the tire by incorporating the pressure transducer and components. electric in a tire / wheel system. In the context of "passive" RF transponders that are energized by an external probe / reader, another problem is to generate predictable and stable voltage levels within the transponder, so that the circuits inside the transponder can perform to their design specification An example of a tire having an integrated circuit transponder (IC) and pressure transducer is described in the US patent. No. 5,218,861, commonly owned, granted on June 15, 1997 to Brown, et al., And incorporated herein by reference. This patent describes an RF transponder mounted inside a tire. When polling (probing) with an external RF signal that is provided by a "reader", the transponder transmits tire identification and tire pressure data in digitally encoded form. The transponder is "passive" since it is not self-energized, but rather obtains its operating energy from the RF signal that is provided externally. The tire has two spaced strips, each including an annular tension member of coiled or wired steel wire. The transponder antenna is positioned adjacent to one of the traction members for magnetic or electrical field coupling to the annular traction member. Another example of a tire having an integrated circuit (IC) transponder and pressure transducer is disclosed in the commonly assigned U.S. patent. No. 5,181,975, issued January 26, 1993 to Pollack, et al., And incorporated herein by reference. As described in this patent, in a tire that has already been manufactured, the transponder can be connected to an inner surface of the tire by a tire patch or other similar material or device. Another example of an RF transponder in a tire is described in U.S. Pat. No. 4,911,217, issued March 27, 1990 to Dunn, et al., and incorporated herein by reference. This patent describes the transponder that has two electrodes, a first of which is placed, such that the average spacing of the surface of the first electrode from one of the tire steel reinforcement components, such as an annular traction member in its strip or a steel reinforcement layer, is substantially less than the average spacing of the second electrode surface from the reinforcement component. Figure 1 of this patent also discloses a prior art identification system ("reader"), which can be used to interrogate and energize the transponder within the tire. The identification system includes a hand-held portable module having within it an exciter and associated circuits for indicating to a user the numerical identification of the transponder / tire in response to an interrogation signal. Typically, in an IC transponder, IC chips and other components are assembled and / or connected to a substrate such as printed circuit board (PCB = Printed Circuit Board). For example, a pressure transducer can be mounted on the PCB and wired either directly to the IC flake or indirectly to the IC flake using conductive traces on the PCB. The PCB substrate is conveniently a reinforced epoxy laminate having a thickness of .508 mm (twenty mils), and a glass transition temperature exceeding 175 C (degrees Celsius). A PCB material Convenient is available in "high performance" FR-4 epoxy laminate, grade 65M90, sold by Estinghouse Electric Corporation, Copper Laminates Division, 12840 Bradley Avenue, Sylmar, CA 91342. In this way it has been previously described, an amount of RF transponders suitable for mounting inside a tire. The environment within which a tire-mounted transponder must operate reliably, including during manufacture and in use, presents numerous challenges to the successful operation of the transducer. For example, the pressure detector used with the transponder will preferably have an operating temperature range of up to 125 C, and should be capable of withstanding a manufacturing temperature of approximately 177 C. For truck tire applications, the pressure detector it should have an operating pressure range of approximately 345 kp (kiloPascals) to approximately 827 kp (approximately 50 psi (pounds per square inch) to approximately 120 psi), and should be capable of withstanding pressure during tire manufacture of up to approximately 2758 kp (approximately 400 psi). The precision, including the sum of all the contributors to its inaccuracy, should be in the order of plus or minus 3% of the full scale. The ability to repeat and the stability of the pressure signal should fall within a specified accuracy range. The transponder must therefore be able to operate reliably despite a wide range of pressures and temperatures. Additionally, a transponder mounted on the tire must be capable of withstanding significant mechanical shocks such as may be encountered when a vehicle passes over a speed bump or bump. Suitable pressure transducers for use with a pneumatic-mounted transponder include: (a) piezoelectric transducers; (b) piezoresist devices such as those described in U.S. Pat. No. 3,893,228 issued in 1975 to George, et al., And in the U.S. patent. No. 4,317,216 granted in 1982 to Gragg, Jr; (c) capacitive silicon pressure transducers, such as described in US Pat. No. 4,701,826 granted in 1987 to Mikkor; (d) devices formed of a conductive conductive ink variable laminate; and (e) devices formed of an elastomeric conductance-variable composition. BRIEF COMPENDIUM OF THE INVENTION A broad object of the present invention is to verify an ambient temperature in the vicinity of an integrated circuit (IC) chip, as defined in one or more of the appended claims, and as such it has the capacity to be built to achieve one or more of the following subsidiary objectives. A broad objective of the invention is to verify an ambient temperature in the vicinity of an integrated circuit (IC) flake, IC flake has functionality other than temperature detection such as a radio frequency (RF) transponder ("tag"), able to transmit data referring to a verified object and parameters associated with the object to an external reader / interpreter. Another object of the present invention is to provide a technique for using the sensed temperature data, in combination with other detected parameter data (such as pressure data), to provide a temperature compensated value for the other detected parameter data. A further objective of the invention is to provide a radio frequency (RF) transponder ("tag"), capable of transmitting data related to a verified object and parameters associated with the object to an external reader / broker.

Another additional objective of the present invention is to provide pressure data from a transponder to an external interrogator / reader, in a manner in which the temperature dependence on the pressure data can be eliminated from the pressure data, resulting in a measurement of Pressure compensated for temperature that is exhibited by an external interrogator / reader. According to the invention, a predictable temperature-dependent temperature of the temperature sensitive component of an integrated circuit (IC) flake, for example the emitter-base voltage (Vbe) of a side bipolar transistor (Ql), is superimposed on through an external precision resistor (Rext). In this way a temperature dependent current I (T) is caused to flow through the external resistor (Rext). The temperature dependent current flowing through the external resistor is provided (for example reflected) to another circuit in the IC flake, the output of which is to provide the temperature dependent current I (T) flowing through the resistor . In one embodiment of the invention, the other circuit is a relaxation oscillator and the output of the other circuit is a temperature dependent frequency. Since the temperature sensor is preferably implemented "in-flake", it will be understood that the IC flake should be a low power device that generates relatively little internal heat, in contrast to the ambient heat that is perceived by the in-flake temperature detector. According to another aspect of the invention, the IC flake functions as the radio frequency transponder (RF), which comprises circuits capable of transmitting unique information to an object with which the transponder is associated with an external interrogator / reader. The temperature sensitive component (temperature detector), and one or more additional detectors (transducers), provide real-time parameter measurement at the transducer site. These measurements are transmitted to the external interrogator / reader, in the form of data, in a data stream in a signal, which is sent out by the transponder, such as when applying (modulation) of the data stream on an RF signal transmitted by the transponder to the external reader / translator. According to one aspect of the invention, the transponder is preferably energized by an RF signal from the external reader / microprocessor. However, it is within the scope of this invention that the transponder is energized by battery. According to one aspect of invention, the transponder is preferably implemented in a single integrated circuit (IC) flake, with a minimum of external means such as an antenna. According to one aspect of the invention, at least one real-time parameter that is measured is the temperature. Preferably, the temperature detector is embedded ("in-flake") in the chip IC of the transponder.

According to one aspect of the invention, an additional real time parameter that can be measured is the pressure. The pressure of preference is measured by a separate pressure sensor ("out-of-flake"), which is preferably of a type that varies its capacitance value as a function of the ambient pressure. Preferably, the temperature sensor is positioned to be substantially subjected to the same ambient temperature as the pressure sensor, so that a pressure compensated by actual temperature can be easily calculated.

According to one aspect of the invention, another additional parameter that can be measured is in the form of an indication that an excessively high temperature condition, in spite of being transient, has occurred. It will be understood that this parameter is different in nature than the real-time parameters of temperature and pressure. An example of a suitable detector for detecting and indicating that this transient excessive temperature condition has occurred can be found in U.S. Pat. Do not. ,712, 609, granted on January 27, 1998 to Mehregany, and collaborators, and incorporated by reference here completely. The Mehregany detector is cited as an example of a Switch for Maximum Temperature Measurement (MTMS = Maximum Temperature Measurement Switch) suitable for use with the transponder of the present invention. Reference is also made to the US patent. No. 5,706,565 which is incorporated herein by reference. The transponder is primarily intended to be associated with a tire, and is preferably located within the tire. However, it is within the scope of this invention that the transponder is associated with another object that is verified as an animal. In a preferred embodiment, the transponder comprises: circuits for receiving an RF signal at a first frequency (Fi) from the external beamer / reader and processing the received RF signal to provide power and clock pulses or synchronization to other circuits; • circuits to control the time window (s) during which one or more real-time parameter measurements are made and captured; • circuits for storing calibration constants; Y • circuits for printing (preferably by modulation of Encryption with Phase Shift (PSK = Phase Shift Keymg)), captured real-time parameter measurements and indication of excessive temperature condition on a signal that is transmitted back to the terminator / external reader to a second frequency (Fe) that is different from the first frequency (Fi). Other objects, features and advantages of the invention will be apparent in the light of the following description thereof. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The drawings are intended as illustrative, not limiting. Certain select elements of the drawings may be illustrated on a non-scale basis, for illustrative clarity. Other similar elements through the drawings may be referred by like reference numbers. For example, element 199 in a figure (or modality) may be similar in many respects to element 299 in another figure (or modality). This relationship, if there are similar elements in different figures or modalities, will be apparent through the specification, including, if applicable, in the claims and extract.

In some cases, similar elements can be referred to with similar numbers in a single drawing. For example, a plurality of elements 199 may be referred to as 199a, 199b, 199c, etc. The cross-sectional views presented herein may be in the form of "slices" or "cross-sectional" cross-sectional views, omitting certain background lines that would otherwise be visible in a real cross-sectional view, for illustrative clarity. The structure, operation and advantages of the present preferred embodiment of the invention will be more apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: Figure 1 is a generalized block diagram of an RF transponder system which comprises an external reader / microprocessor and an RF transponder within a tire, according to the prior art; Figure 2 is a block diagram of major components of an RF transponder, in accordance with the present invention; Figure 3 is a schematic diagram of major portions of the RF transponder of Figure 2, in accordance with the present invention; Figure 3A is a schematic diagram of a portion of the RF transponder of Figure 2, according to the invention; Figure 3B is a schematic diagram of a portion of the RF transponder of Figure 2, according to the invention; Figure 3C is a diagram of a memory space within the RF transponder of Figure 2, illustrating how data can be arranged and transmitted, according to the invention; and Figure 4 is a schematic block diagram of a receiving portion of a coater / reader, according to the invention. DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates a transponder system of RF 100 of the prior art, comprising a radio frequency (RF) transponder 102 disposed within (eg mounted on an interior surface of) a tire 104. An antenna, not shown, is mounted within the tire 104 and is connected to the transponder 102. The transponder 102 is an electronic device, capable of transmitting an RF signal comprising unique identification information (ID) (for example its own serial number, or an identification number of the object with which it is associated) in this example, tire 104) as well as indicative data of parameter measurement such as ambient pressure detected by a detector (not shown) associated with transponder 102 with an external reader / reader 106. External interrogator / reader 106 provides an RF signal for interrogating transponder 102, and includes a bar reader 108 having an antenna 110, a display panel 112 for displaying information transmitted from the transponder 102 and controls (switches, buttons, knobs, etc.) 114 for a user to manipulate the functions of the corruptor / reader 106. The present invention is directed primarily to implementing the RF transponder. However, certain functionality for a reader / reader to be compatible with the transponder of the present invention is discussed below with respect to Figure 4. As is known, the parameter measurement information and / or ID can be encoded ( applied) in a variety of ways in the signal transmitted by the transponder 102 to the reader / interrogator 106, and subsequently "de-encodes" (retrieves) in the interrogator / reader 106 to display the user. The RF transponder 102 can be "passive" since it is energized by an RF signal generated by the external reader / interrogator 106 and emits by the antenna 108. Alternatively, the RF transponder can be "active", since it is energized by battery. Transponder systems such as the transponder system 100 described herein are well known. Figure 2 is a block diagram of the RF 00 transponder (compare 102) of the present invention, illustrating the main functional components. The transponder 200 is preferably implemented in a simple integrated circuit (IC) chip within the dotted line 20, to which a number of external components are connected. Other dotted lines in the Figure indicate major functional "blocks" of the transponder 200, and include a transponder "core" 204 and a detector interface 206. The components external to the IC 202 flake include an antenna system 210, comprising an antenna 212 and a capacitor 214, connected through coil 212 to form an LC resonator tank circuit, an external precision resistor ("Rext") 216, a capacitor for external pressure detection ("Cp") 218, and a switch for optional external maximum temperature measurement ("MTMS") 220. The antenna may be in the form of a coil antenna, a loop antenna, a dipole antenna and the like. Alternatively, the signal output by the transponder can be provided on a transmission line. Mainly below, it describes a transponder having a coil antenna. Transponder core 204 includes phase circuits 222 for processing an RF signal, such as an unmodulated carrier signal of 125 kHz (kilohertz) received by antenna 212, to rectify the received RF signal and to provide voltages to energize other circuits in IC 202 flake. For example, the interface circuits provide a regulated supply voltage (Vdd) of 2.5 volts, and a temperature independent band gap voltage (Vbg) of 1.32 volts. The provision of various supply and reference voltages for the transponder circuit is described in more detail below with reference to Figure 3B. The mterfase 222 circuits also provide the received RF signal, preferably at the frequency (Fl) in which it is received, to a clock generator circuit 224, which generates clock signals in a known manner to control the synchronization of other circuits in the IC 202 chip as well as the frequency (Fe) of a signal that is transmitted by the transponder to the external interrogator / reader. A sequencing circuit / synchronization generator 226 receives the clock pulses from the clock generator circuit 224 and processes (eg divides) the clock pulses to generate synchronization windows (t and WP, described below), by predetermined periods of time during which the parameter measurements are made (eg temperature and pressure). The synchronization windows (Wt and WP) may be of substantially equal duration or of different duration. The sequencing / synchronization generator circuit 6 also controls the synchronization and sequence of various functions (eg measuring and capturing pressure, measuring and capturing temperature, described in more detail below) performed at detector interface 206, and preferably it is implemented as an algorithmic state machine (ASM = Algopthmic State Machine). The transponder core 204 further includes a counter / register circuit 230 which includes a temperature register 232 (for example 12-b? Ts) and a pressure register 234 (for example 12-b? Ts) for capturing and storing measurement of temperature and pressure (counts), respectively, and an addressable memory block 236 including an EEPROM structure. The registers 232 and 234 and structure EEPROM 36 are illustrated in dashed lines 238 which represent a block of addressable memory in the IC flake. The counter / register circuit 230 also includes a multiplexer and column decoder 240, as well as a row decoder 242 to control the sequence in The signals (eg data) are output on a line 244 to a modulation circuit 246 which, by the interface circuits 222, communicates selected tire operation characteristics in a data stream by the antenna method. 210 to the external reader / broker (106, Figure 1). The transponder core 204 also includes a baud rate generator 248, controls the rate at which the modulation information (e.g., temperature or pressure measurement) is applied to modulation circuits 246. The baud rate generator 48 also provides a clock with data transport that controls the output frequency (Fe) of the transponder and a data rate clock that controls a speed at which the data stream including measurements, calibration information, etc., is modulated in the carrier of the transponder output. Detector module 206 includes a circuit 50 for generating an output current I (T) on a line 51 that is related to a predictable characteristic voltage of a temperature sensitive component (for example Vbe of a Ql transistor, described below) which is superimposed on the external resistor (Rext) 216. The output current I (T) on line 51 is provided to a current steering circuit 252 and to an oscillator of relaxation 254. In general terms, the relaxation oscillator 254 oscillates at a frequency controlled by a voltage change rate (dV / dT) produced at an output line 253 from the current direction circuit 252. The rate of change The voltage on line 253 is a function of the output current I (T) on line 251 and internal capacitance (CFX) associated with the relaxation oscillator, as well as an external capacitance (Cp) that can be switched in the circuit oscillator. An output signal of the relaxation oscillator 254 is provided on a line 255 which, as will be explained in more detail below, is indicative of both the ambient pressure and the ambient temperature. As used herein, the term "ambient" refers to the parameter that is measured in the vicinity of the transponder, more particularly in the respective sensors associated with the transponder. When the transponder is mounted inside a tire, "ambient pressure" refers to the pressure inside the tire. In operation, an RF signal from an external source (ie reader / interrogator, not shown, compare 106, FIG. 1) is received by antenna 212. This RF signal is rectified and used to energize the RF 200 transponder. of modulation applied to the modulation circuit 236 is used to alter characteristics of the antenna method (for example, impedance, resonant frequency, etc.). These alterations are detected by the external beamer / reader and decoded, providing feedback information of temperature and back pressure from the RF 200 transponder to the external beamer / reader. The sequencer / synchronization generator circuit 226 controls whether the current I (T) on line 251 is "routed" on one or the other of the two capacitors (CFX1 or CFX2, described below with respect to the relaxation oscillator 312) associated with the relaxation oscillator 254, and whether the capacitance for external pressure detection (Cp) 218 is or is not included in the generation of an output signal (Fose) by the relaxation oscillator 254. For example, to measure the temperature, the current I (T) is directed to the internal oscillator capacitors (CFX), but the pressure detector capacitor (Cp) is disconnected from (not included in) these capacitances. This means that the frequency of the oscillator output signal seen on line 255 is a function of temperature alone. When the pressure sensing capacitor (Cp) 218 is "switched on", then the output frequency of the oscillator 254 on the line 255 as will be explained in more detail below, will be a function of both the pressure and the temperature. As described in more detail below, a reader / probe algorithm is employed to generate a temperature independent pressure measurement. As controlled by the sequencing circuit / synchronization generator 226, either the temperature record of 12-b? Ts 232 or the pressure register of 12-bits 234 (depending on whether the temperature or pressure is measured) counts (captures) ) oscillations of the oscillator output signal on line 255. (Counters, not shown, are associated with these "registers"). The synchronization "window" that is provided by the sequencer / synchronization generator circuit 226 has a controlled, known duration. As a result, the count remains on (captured by) the respective temperature or pressure counter (register), when the synchronization window "closes", is a function of (proportional to) the oscillation frequency (Fose) of the relaxation oscillator. 254, and therefore a function of temperature or pressure, whichever is measured. The EEPROM structure 236 is used to maintain the calibration constants that the reader system uses to convert temperature and pressure counts (Nt and Np, respectively described in more detail below) into temperature and pressure readings that can be displayed (for example through the display 112) to a user. The EEPROM structure 236 can also store the transponder ID, calibration data for the transponder, and other particular data to the particular transponder. Figure 3 is a more detailed schematic diagram 300 of the various components of the transponder 200 of Figure 2, primarily the components described previously with respect to the detector interface section 206 of Figure 2. In this schematic diagram 300, they are employed Conventional circuit symbols. For example, lines that cross each other do not connect to each other, unless there is a "point" at their junction (junctions), in which case, the lines connect to each other. Conventional symbols are used for transistors, diodes, ground connections, resistors, capacitors, switches, comparators, inverters and logic gates (for example "Y", "NO-Y", 0"NO-O" (AND, NAND, OR ÑOR) The circuit is described in terms of a CMOS mode, where "P" (for example "Pl") indicates a PMOS transistor (P-channel) and "N" (for example "NI") indicates an NMOS transistor (channel -N) The CMOS transistors are of the transistor type with field effect (FET = Field Effect Transistor) each one that has three "nodes" or "terminals" that is to say a "source" (S = Source), a discharge (drain = D), and a gate (gate = G) that control the flow of current between the source and the discharge. In the description that follows, it will be evident that an amount of the PMOS and NMOS transistors are "connected by diodes", which means that their discharge (D) is connected to their gate (G). The general theory of operation of transistors, particularly CMOS transistors, is well known to those of ordinary skill in the art to which it relates more closely in the present invention. As will be apparent from the description that follows, a number of CMOS transistors are connected in a "current reflector" configuration. The concept of a current reflector is well known, and in its simplest form it comprises two transistors of similar polarity (for example two PMOS transistors) which have their gates connected to each other and one of the pair of transistors is connected by diode. Current reflection generally involves causing a current to flow through the diode-connected transistors, resulting in a gate voltage in the diode-connected transistor required to produce this current. In general, the gate voltage of the diode-connected transistor is forced to become any voltage that is necessary to produce the reflected current through this transistor. Since the diode-connected transistor, by definition, has no gate current, by applying the gate voltage of the diode-connected transistor to any other connected transistor in the same manner, a current reflected through the identical connected transistor will flow. Typically, the reflected current transistors all have the same physical area, in which case, the reflected current will essentially be the same as the current that is reflected. It is also known to produce a reflected current that is already greater than or less than the current that is reflected by making one of the transistors physically larger or smaller (in area) than the other. These identical connected transistors have different areas, they are connected in a current reflected configuration, their areas in scale (higher or lower) will produce corresponding scale current (higher or lower). In the main part below, the numerous connections between the various components of the circuit are clearly illustrated in the Figure, and the descriptive emphasis is on the various functions of interactions between the various components of the circuit rather than describing (ad nauseam) and all and each of the individual connections between the various components, all of which are explicitly illustrated in the Figure.

Antenna system 210 comprises a coil antenna 212 and a capacitor 214 connected through antenna 212 to form a resonant tank circuit LC that provides an alternating current (AC = Alternatmg Current) output to a full-wave rectifier circuit 302. The full-wave rectifier circuit 302 comprises two PMOS transistors and two diodes connected in a conventional manner, as illustrated, and outputs a rectified full-wave direct current (DC) voltage on a line 303. A capacitor 304 is connects between line 303 and ground to "smooth" (filter) variations ("ripples") in the full-wave rectified DC voltage on line 303. The voltage on line 303 in this way becomes a useful voltage for the components remaining of the transponder - in this case, a positive supply voltage (Vcc) on line 303. A temperature detection circuit 306, corresponding approximately to the converter d e base-emitter voltage-to-cable 250 of Figure 2, is connected between line 303 (Vcc) and ground, and includes four CMOS transistors labeled Pl, P2, NI and N2 and a lateral bipolar transistor labeled Q1, and connects to external resistor 216 (Rext). Transistors P2 and NI are connected by diode as illustrated. The two transistors Pl and P2 are connected in a reflected current configuration, and two transistors NI and N2 are also connected in what can generally be considered as a current reflected configuration. The source of the transistor NI is connected by the transistor Ql to ground, and the source of the transistor N2 is connected by an external resistor (Rext) 216 to ground. As will be evident, the ability of the temperature sensing circuit 306 to produce a signal (i.e. a current), which is proportional to a detected temperature (ambient) (e.g. within the tire with which the transponder is associated), primarily it depends on the characteristic that the base emitter voltage of transistor Ql is a highly predictable and repeatable function of temperature. The resistor (Rext) 216 is an external resistor, precision, and reference, whose value is substantially independent of the temperature (in contrast to the temperature dependence of the transistor Ql). A suitable value for the resistor (Rext) 216 is 20.5 K. The transistor N2 is connected between the transistor P2 and the external resistor 216 (Rext) in a "source-follower" mode. As a voltage is applied to the gate of transistor N2, its source voltage will "follow" its gate voltage (minus an inherent voltage drop).

(Vgs) between its gate and its source). As the current flows through transistor NI, its gate voltage will be displaced by its gate-source voltage drop (Vgs) over the emitter voltage in transistor Ql. Since the NI and transistors N2 are essentially identical, with the same current flowing through each of the two NI transistors and N2, they will have identical gate-source voltage drops (Vgs). As a result, the voltage at the source of the transistor N2 through the external resistor 216 (Rext) will be essentially identical to the voltage at the emitter of the transistor Ql. Therefore, when applying Ohm's law (E = IR, or I = E / R), the current through the external resistor 216 (Rext) will be equal to the emitter voltage of the transistor Ql divided by the resistance of the external resistor 216 (Rext). In normal operation, all the current flowing through the external resistor (Rext) 216 circulates through the source of the transistor N2 and consequently through the transistor connected by diode P2. By a reflected current connection, the current through transistor P2 is replicated (reflected) in transistor Pl and further replicated (reflected) in transistor P4. This ensures that the current flowing through the NI and N2 transistors will be the same, at all times, it will help additionally to ensure that the emitter voltage in the transistor Ql and the voltage across the external resistor (Rext) 216 are identical, independent variations in voltage and process. As previously mentioned, transistors NI and N2 are connected in what can generally be considered as a current reflected configuration. However, they are not strictly connected identically, their function in circuit 306 is mainly to "couple" Ql and Rext. In essence, the circuit 306 ensures that the current I (T) flowing through the external resistor (Rext) is predictable and is a function of the absolute temperature (T) of the transistor Ql. As described in more detail below, this temperature dependent current I (T) circulates through the external resistor (Rext) 216 is reflected to a relaxation oscillator (312, described below) to provide a signal indicative of temperature of transistor Ql to the external reader (106, Figure 1). As described in more detail below, the output frequency (Fose) of the relaxation oscillator 312 will be a function of the absolute temperature (T) of the transistor Ql. At this point, it is useful to note that it is essentially the transistor Q1 which is used as the temperature sensing element of the total transponder circuit. He The transponder circuit advantageously employs an inherent characteristic of this transistor implemented in CMOS technology that the basic emitter voltage of transistor Ql will vary by a predictable amount of -2.2 mv / C (millivolts per degree Celsius). It will be noted that the transponder of the present invention is described in terms of a "passive" device that relies on RF energy supplied thereto by an external source (106, Figure 1) to energize its circuit. However, it is within the scope of this invention that the transponder contains its own power supply such as in the form of a battery. In any case, when the circuits are first energized as described with respect to the temperature sensing circuit 306, it is important to ensure that they "ramp up" to their normal operating state from their quiescent state in a reliable and predictable manner ( controlled). For this purpose, two lines 305 and 307 are illustrated which are connected between the temperature sensing circuit 306 and a "start" circuit 308. The starter circuit 308 is connected between the supply voltage (Vcc) on line 303 and ground, and serve two main purposes: (i) to obtain current circulating in the temperature sensing circuit 306 when the transponder (200) first starts from a de-energized state; and (11) to reflect and convert the current flowing through transistor P2 from a supply reference current to a ground reference current. The start is started by transistor P3. Transistor P3 is manufactured to have high channel resistance, in order to operate in a "weak start" mode. With its gate connected to ground, it will always be "on", and will behave essentially like a resistor that has a slightly high resistance (for example> 10k ohms). Since, in the beginning, no current circulates elsewhere in the circuit, transistor P3 operates to bring the gate of transistor N3 towards the supply voltage (Vcc), thereby "activating" transistor N3, which effectively connects the source of the transistor N3 to its discharge, which in turn causes the current to flow through the connected diode transistor P2 of the temperature detection 306 in the discharge of the transistor N3. This causes the voltage at the source of transistor P2 to decrease, thus causing the current to flow in transistors Pl and P4. As current flows through transistor P4 in the connected transistor of diode N5, a reflected current connection between transistors N4 and N5 causes a corresponding current flows through transistor N4, thereby bringing the gate of transistor N3 to ground, and thus effectively "off" the current flow through transistor N3. However, with current now flowing through the reflected transistors of current Pl, P2 and P4, the current flowing from the transistor Pl through the transistor NI in the transistor Ql forces the temperature sensing circuit 306 to "start" "in its stable operating point state (instead of its zero current state). After start-up, transistor N3 essentially "detaches" from the circuit having performed its intended function. The transistor N5 is connected in a current reflected configuration with the transistor N4 (and, as described below, with the transistor N6). Therefore, essentially with a current equivalent to the current through the external resistor (Rext) 216 circulating through the transistor N5, the same current flows through the transistor N4, thus establishing a reference voltage (Nbias) on line 309. The reference voltage (Nbias) on line 309, as well as a supply voltage (Vdd) on a 309 Y line is provided to a current scaling circuit 310. The supply voltage (Vdd) on line 309 'is provided in any convenient form, such as a multiple of a band gap voltage (Vbg) generated in a conventional manner elsewhere in the chip, and its magnitude (eg example 1.32 volts) should be independent of temperature, as is inherent in the silicon process used to produce the flake. Providing this stable voltage (eg band space) (eg Vbg) and the supply voltage (eg Vdd) derived therefrom, is well within the reach of a person with ordinary skill in the art to which it refers more closely the present invention, and is described in more detail below with respect to Figure 3B. The current scaling adjustment circuit 310 is constructed in the following exemplary manner. The sources of transistors P5 and P6 are connected for supply voltage Vdd. The gate of a transistor N6 receives the reference voltage (Nbias) on line 309. The transistor N6 is connected in a reflected current configuration with the transistor N5 (as well as the aforementioned transistor N4) and therefore reflects the flow of current I (T) through transistors N4 and N5. Consequently, the flow of current through the transistor connected by diode P5 reflects the current flow through transistors N4, N5 and N6. The transistors P5 and P6 are connected in a current-reflow configuration, but are manufactured (using conventional CMOS manufacturing techniques) such that the current flowing through the transistor P6 is scaled down or up by a ratio (N) from the physical area of transistor P5 to the physical area of transistor P6. For example, if transistor P6 is smaller in size than transistor P5 (ie transistor P5 is "N" times larger in area than transistor P6), then the current flowing through transistor P6 will be proportionally ( N times) smaller than the current flowing through transistor P5. In this manner, the "scale adjusted" current flowing through transistor P6 is labeled "I (T) / N" in the Figure, and is provided on a line 311 to a 312 relaxation oscillator circuit. It is known that the ratio of the currents between transistors P5 and P6 can be easily established by conventional circuit processing techniques, such as by simply making one of the transistors larger than the other, or by implementing one of the two transistors as the aggregate of two or more transistors of the same size, so that their aggregate area is greater that the other area of the two transistors. The relaxation oscillator circuit 312 is of substantially conventional design and includes two pairs of transistors at the "front end" of each of these two phase paths - a pair of complementary transistors P7 and N7 at the front end of a path of one phase (fl) 314a, and another pair of complementary transistors P8 and N8 at the front end of another phase path (f2) 314b. Connected as illustrated, for a given pair of transistors (for example P7 and N7), when its common gate voltage is high (ie towards the positive supply) its output will be grounded, and when its common gate voltage is low, will provide the current I (T) / N that circulates on line 311 to a respective one of the phase paths (for example 314a) of the relaxation oscillator 312. As is known, in this arrangement, when the gate voltage common one of the pairs of transistors (for example P7 and N7) is high, the common gate voltage of the other pair of transistors (for example P8 and N8) will be low and vice-versa. In this way, each phase path 314a and 314b has a service cycle (ie its "on" time), which may be the same as or may be different than the service cycle of the other path. of phase 314b and 314a, respectively. In this way, each pair of transistors (for example P7 and N7) can be considered as a "power switch" to their respective phase path (e.g. 314a). Each phase path 314a and 314b of the relaxation oscillator 312 has a comparator 316a and 316b respectively, in its power supply and has a fine-value capacitor Crxl and CFX2, respectively, connected between the negative (-) supply of the comparators 316a and 316b and earth. The Cral and CFX2 capacitors have exemplary capacitance values of 2-5 pf (picofarads) and 2-5 pf, respectively, and are preferably implemented as "in-flake" devices, such as poly-a-poly capacitors, which exhibit a low temperature coefficient (for example less than 20 ppm). The positive (+) (terminal) feeds of comparators 316a and 316b are linked together and set to a reference threshold voltage Vbg, such as 1.32 volts, which is independent of temperature. A logic gate "NO-0 (ÑOR)" 318a and 318b, are connected to the output of each phase path 314a and 314b, respectively and the two gates NO-0 (ÑOR) 318a and 318b are cross-connected to form a circuit of interlocking that has an outlet on a line 319. The cross-linked NO-0 (ÑOR) gates 318a and 318b of This way they are able to function as a swingarm or an interlocking RS (re-start / micio). When the common gate voltage of one of the power switches (for example P7 and N7) is high, the respective capacitor (for example Cn ,,) for this phase path (for example 314a) is grounded (it is set in short, caused by being lacking in charge). On the contrary, when the common gate voltage of one of the power switches (for example P7 and N7) is high, the current set in scale I (T) / N is applied to (let it circulate in) the respective capacitor (for example Cral) for this phase path (for example 314a), and the capacitor starts charging (acquiring an increased voltage across the capacitor). When the voltage across the capacitor reaches the comparator reference voltage (for example 1.32 volts) the output of the comparator goes to a low value and changes the state of the interlock 318a / 318b on line 319. In this way, the oscillator of Relaxation will oscillate at a frequency (Fose) determined by the rise time of the CFX1 and CFX2 capacitors and importantly by the I (T) / N scale current supplied to the capacitors CFX1 and Cf ^ - With higher current I (T ) / N supplied, the voltages of the CFX1 and CFX2 capacitors will rise faster, crossing the threshold voltage more fast, and causing the relax oscillator 312 to oscillate faster, thereby increasing the frequency of the Fose signal on line 319. The Fose signal on line 319 is inverted by an inverter 320, as illustrated, to provide a Fose 'signal on line 321. As described in greater detail below, oscillator 312 is controlled to operate in two mutually exclusive modes, a temperature detection mode (between times tO and ti) and a detection mode of pressure (between times ti and t2), as controlled by the sequencer / synchronization generator 226. The frequency of the output signal from the Fose (and Fose1) oscillator will be different in each of these two modes. GENERATING PRESSURE AND TEMPERATURE SIGNALS In the exemplary context of the transponder 200 associated with a tire, it is primarily convenient to determine the pressure within the tire. For example, a typical passenger vehicle tire can be adequately inflated to approximately 221 kp (approximately 32 psi). For example, it is estimated that a decrease of approximately 10% in fuel consumption can be achieved if the tires in the vehicle are operated at their specified pressure.

Typically, they are sensitive to this aspect and check and adjust the tire pressure frequently, the average operator of a passenger vehicle is often less inclined to take a look at the tire pressure until, for example, the tire is visibly low. In these cases, a liquid crystal display (LCD = Liquid Crystal Display) or similar on the dashboard of a vehicle can provide dynamic tire inflating information to the operator of a vehicle, the tires of which are equipped with a transponder just like the one described here. With no less significance is the emergence of tires "that work without being inflated" distributed in the market by various tire manufacturers. The Goodyear Extended Mobility Tire tire series (EMT) is an example of a frl tire, a general purpose of which is to allow a driver to drive up to approximately 120 kilometers (50 miles) with a flat tire at speeds of "reasonable" operations (for example, 144 kilometers per hour or 60 miles per hour) while maintaining normal control over the vehicle. These tires that function without being inflated are generally well known, and do not form a portion of the present invention per se. When a tire works without being inflated, it is particularly It is important for the driver to be aware of the fact that he operates the vehicle on "borrowed time" as indicated, mainly by a visual or audio indication (eg a buzzing sound) that the tire is definitely deflated and needs to be repaired or replaced at your earliest convenience. By allowing the 312 relax oscillator to run, the frequency of its output signal Fose (and Fose1) will be a function of the absolute temperature of (detected by) the transistor Ql. This is true both in the temperature detection mode and in the pressure detection operation mode in the temperature detection mode, and in the case that the capacitance values for CFX1 and CFX2 are equal, which is preferred, Relaxation oscillator 312 will have a symmetrical service cycle (balanced, 50%). In the pressure sensing mode, the pressure sensing capacitor (Cp) 218 is switched by a semiconductor switch 350 through Cra2, which changes the service cycle and output frequency Fose (and Fose ') of the relaxation oscillator. . In the temperature detection mode, only Cral and CFX2 fixed capacitors are charged alternately (and discharged) resulting in a service cycle of 50% with a period proportional to the ambient temperature. In the mode of pressure sensing, the pressure sensing capacitor (Cp) 218 is switched on the phase path 314b of the oscillator 312. Thus, for a given temperature, for the first half of the oscillator period the phase path 314a behaves in the same way as in the temperature detection mode and the second half of the oscillator period, the phase path 314b, behaves in a way that is proportional to the capacitance value of the fixed capacitor Cra2 plus the capacitance value of the capacitor of pressure detection (Cp) 218. This in effect, brakes the oscillator and changes its duty cycle. The change in the service cycle is indicative of the ratio of Cp to CFX2. Thus, from the relationship of the two periods (with and without Cp in the circuit, it is direct to calculate which is the additional capacitance Cp therefore the detected pressure.) As described in more detail below, the dependence of The temperature of the oscillator output in the pressure detection mode can be completely eliminated in a direct way.The "braking" of the oscillator when the pressure sensing capacitor (Cp) 218 is switched in the oscillator circuit, inevitably results in Relatively smaller oscillator output pulses (reduced output frequency) to count during a window of pressure measurement determined (for example Wp) that during a temperature measurement window of similar duration (for example Wt). In other words, a "braking" oscillator will reduce this rate at which accounts indicative of the measurement of parameters are collected. In order to increase the resolution (amount) of the accounts (Np) generated during the pressure measurement window (WP), it is contemplated that the pressure measurement window (WP) may increase in size (change in duration) to allow capturing an appropriate number of pressure counts in the pressure register 234. This can be easily achieved simply by setting a larger value (than otherwise) for time t2 that sets the end of the window for pressure measurement ( Wp) in the pressure detection mode (between times ti and t2), as controlled by the sequencer / synchronization generator 226. For example, the temperature measurement window Wt (between the times tO and ti). ) may be in the order of several (for example eight) milliseconds and the window for pressure measurement Wp may be in the order of tens or dozens (for example forty) milliseconds. Alternatively, it is contemplated that the current in scale (I (T) / N) flowing out of the adjustment circuit in scale 310 to the relaxation oscillator 312 may be increased during the window for pressure measurement (W?) To increase the fundamental frequency of the relaxation oscillator 312, thereby increasing the total resolution of the pressure count. This can be easily achieved for example in the case that P6 is smaller in size (area) than transistor P5, simply by switching on a transistor P6 '(not shown) instead of transistor P6, transistor P6' has an area larger than the transistor P6 so that the ratio of the areas of the transistors P5 and P6 is closer to the unit (ie less reduced in scale) and the current to the relaxation oscillator 312, therefore its counting speed. This switching of another transistor P6 'is easily effected with a switch (not shown) comparable with the aforementioned switch 350 which switches in the pressure sensing capacitor (CP) 218. A person with ordinary skill in the art to which more closely The present invention will easily understand how to shift the "braking" of the oscillator when the pressure sensing capacitor (CP) 218 is switched in the oscillator circuit, in light of the teachings presented herein. MEASUREMENT PARAMETERS When the transponder is energized, the temperature and pressure are measured continuously and these measurements are transmitted back to the external reader / interrogator (106) as data words in a data stream. For example, each of the temperature and pressure parameters can be transmitted back to the reader / interrogator (106) as data words of 12-b? Ts, as selected (known) portions of a larger data stream (e.g. 144-b? Ts). A bit in the total data stream can be dedicated to the state (eg "closed" or "open") of the MTMS switch (220). A complete description of an exemplary data stream transmitted by the transponder to the external reader / interrogator is set forth below with reference to FIG. 3C. The temperature is conveniently measured by counting the number of cycles that are sent out from the oscillator 312 for a fixed period of time (time window of tO to ti)) with a period T ". For example, a descending counter (associated with the temperature register (232)) can be synchronized by the oscillator, such that at the end of the window Wt a temperature count Nt is generated. The relationship between Nt and the temperature is linear. OPTIMIZING PRESSURE RESPONSIVITY Obtaining (and displaying) an accurate pressure reading is of paramount importance when verifying tire pressure, certain circuit parameters The transponder can be set to maximize its response under pressure and thereby improve the pressure reading accuracy exhibited by the external reader / shooter (106). As previously described, the transponder responds to the pressure detector change capacitance (CP) 218 by changing the value of a binary 12-bit word that is transmitted to the external reader / interrogator (106). This binary word is the count of an oscillator frequency during a synchronization window WP (between ti and t2) established by the synchronization generator / sequencer 226. The pressure response can therefore be described as the change in accounts per change. unit in capacitance to the capacitor for pressure detection (CP) 218. The pressure response of the transponder has been found to depend on a number of factors, each of which can be analyzed. For example, it has been determined that. (a) increase the current adjusted in scale I (T) / N to oscillator 312 will proportionally increase the NP pressure counts for a given value of the capacitor for pressure detection (CP) 218; and (b) decrease the value for CFX1 and CFX2 and proportionally increase the NP pressure accounts for a determined value of the capacitor for pressure detection (CP) 218; and (c) increasing the current I (T) / N to the oscillator will proportionally increase the NP pressure counts (for a given value of CP) at a higher speed than decreasing the values of Cm and CFX2. As a general proposition, increasing NP pressure accounts is convenient. However, a person of ordinary skill in the art to which the present invention more closely relates will readily appreciate that there is a practical upper limit to increase the pressure counts at a frequency which may become unacceptably large for the capacity of certain circuits. of IC flake. OBTAIN A PRESSURE READING IN THE READER / INTERROGATOR The fundamental frequency of the oscillator 312 is executed by parameters in the IC flake (for example 204) and are previously described, depending on the temperature. Therefore, the pressure response is a (hybrid) function of both temperature and pressure and the ratio of NP to CP is non-linear. Therefore, using a linear equation to calculate the pressure response will inevitably lead to significant errors over a range of measured pressures. (For limited ranges of measured pressures, for example over a pressure range of 138 kp (20 psi), using a line equation, however, may be acceptable). An important advantage of using the transponder circuit described previously is that the relationship between NT / NP to the pressure detector capacitance is linear and does not require a temperature compensation term in the equation (algorithm) used by the reader / interrogator (106) to calculate the pressure, in this way greatly simplifying the design of the reader / interrogator. This beneficial "quotient" relationship is easily demonstrated by the following equations: (equation 1) Nt = T "* I (t) / (2 * Vbg * CFX) (equation 2) NP = TW * I (t) / ( Vbg * (2 * CFX + CP)) solving for NT / NP the following is concluded: (equation 3) NT / NP = 1+ (CP / 2 * CFX) In this way it can be observed that the relation NT / NP is only a function of CP and C ^, and no other variables. This means that Nt / Np is only a pressure function, and is insensitive to temperature or load current variations. Figure 3A illustrates the components involved in the final stage of capturing temperature and pressure measurements in the transponder. The signal Fose 'output by the relaxation oscillator 312 is provided to a feed of each of two Y gates (AND) 360 and 362. One signal ("Temp Capture") is provided by the synchronization sequencer / generator 226 to the other input of the Y (AND) 360 gate during the temperature detection window (Wt), in order to load the temperature counter / register 232 with the count (data) Nt indicative of the measured temperature. Another data signal ("Pressure Capture"), is provided by the sequencer / synchronization generator 226 to the other input of gate Y (AND) 362, during the pressure detection window (Wt) in order to load the counter / Pressure register 234 with the (data) NP account indicative of the measured pressure. These signals are then moved out of the registers 232 and 234, by the MUX 240, to the modulation circuit 246 previously described. GENERATE RELIABLE SUPPLY AND REFERENCE VOLTAGES As previously described, the positive (+) (terminal) feeds of comparators 316a and 316b are linked together and set to a reference "bandwidth" voltage Vbg, such as 1.32. volts, which is independent of temperature. As also previously mentioned, the supply voltage (Vdd) on line 309 'can be provided as a multiple of the reference band gap voltage (Vbg) so that it is a stable operating voltage for the address circuit of current 310 and relaxation oscillator 312.

Figure 3B illustrates a circuit 370 suitable for generating the supply voltage Vdd. A temperature independent calculable band gap voltage Vbg is easily derived, based on the processing techniques employed to fabricate the IC flake, as is inherent in the selected process (e.g. CMOS). This band gap voltage Vbg is provided to the "+" power supply in an operational amplifier 372, connected as illustrated, in a feedback loop having gain, to provide supply voltage Vdd as an integral multiple of the room voltage. Vbg band AN EXEMPLARY DATA CURRENT As mentioned above, information (data) of the transponder is transmitted to the external reader / reader in the form of a data stream, a portion of which is the temperature count Nt, another portion of which is the account of pressure NP, and another portion of which represents the state (for example "closed" or "open") of the MTMS switch (220).

Remaining portions of the data stream may contain information that is customized to a particular transponder unit such as ID information (for example, serial number), calibration constants and the like.

Figure 3C illustrates an exemplary architecture for information that is stored (in memory) within the transponder, as well as a stream of data that is transmitted by the transponder to the external reader / browser. The memory of the transponder core 204 has for example a 144-b? Ts address space that includes 119 (one hundred nineteen) programmable memory bits and an address location dedicated to the state of the switch MTMS 220, these 120 (one hundred twenty) programmable memory bits constitute the EEPROM (136), plus the two registers of 12-b? Ts 232 and 234. Each of the 119 bits of programmable memory can be written separately with any combination of data, including synchronization pattern information (smc), general data, error verification codes and temperature and pressure calibration data. The EEPROM is "for block writing", which means that in the "write" mode, all 120 bits of EEPROM are programmed to a logical (binary) value of "1". Individual bits can be "erased" or set to a logical value of "0", simply by synchronizing the flake to its physical address and placing the flake in the "erase" mode. The address location is retained. In this example, the first twelve data locations (000..011) in ROW 1 are reserved for smc. The The following seventy-one data locations (012,082) in ROWS 2 through 7 are for general information and a value for a data validation algorithm such as a Cyclic Redundancy Check (CRC). The following data location (083) contains the logical level (state) of the MTMS switch 220. A logical value of "1" indicates that the MTMS switch is open and a logic value of "0" indicates that the MTMS switch is closed. The transponder unit is conveniently calibrated before it is installed on a tire. This basically involves determining the slope and intercepts for temperature and pressure values generated by the transponder at various pressures and temperatures in a test chamber, and programming these characteristic calibration values associated with the transponder in the memory space. The next twelve data locations (084,095) in ROW 8 maintain temperature calibration data (eg, intercept) ("TEMP COMP"). The next twelve data locations (096..107) in ROW 9 maintain pressure calibration data (eg intercept) ("PRESS COMP"). The next twelve data locations (108..113 and 114..119) in ROW 10 maintain calibration-dependent information for temperature and pressure, respectively. In accordance with an aspect of the invention, it has been determined that characteristic values for the NT / NP slope, or the "related" response of the temperature count divided by the pressure count, is line with respect to the value of the capacitor for CP pressure detection and to use this value The ratio of NT / NP does not require a temperature compensation term in an equation used to calculate the pressure. Additionally, it has been determined that the NT / NP quotient value is less sensitive to variations in coupling between the reader / translator and the transponder than any of these measurements taken alone. In this way, by determining (during calibration) and storing calibration data for the NT / NP quotient value in the transponder, the ability to determine an actual pressure reading that is relatively insensitive to coupling variations between the reader / interrogator and the transponder is both simplified and more reliable. This quotient calibration value for NT / NP is stored in the transponder memory and included in the data stream transmitted to the external reader / interrogator. As Nt and NP accounts are generated for temperature and pressure as previously described, stored in ROWS 11 and 12 of the total memory space corresponding to the temperature and pressure registers 312 and 314, respectively. Various defaults can be stored to indicate short circuit and spill conditions. OPERATING AND MODULATING FREQUENCIES The transponder of the present invention is not limited to any particular operating frequency. The selection of the frequency of operation will depend substantially on factors such as, where the transponder is mounted, in relation to the object being verified, the location of the reading antenna (108), and the relevant governmental regulations that allow (on the contrary , restrict) data transmissions of the type established here in select portions of the total RF frequency spectrum. An example of convenient operating frequencies for operating the transponder in the U.S.A. is 60 KHz to 490 KHz. The transponder can be polled (and energized) by the reader / interrogator at a first "interrogation" frequency (Fi), and the data stream can be transmitted back to the reader / interrogator at a second "data carrier" frequency (Fe ) that conveniently is a whole number or fraction number of the interrogation frequency. For example, Fe = Fi / 2.

O, Fe = Fi / 4. The frequency (Fe) at which the data stream is transmitted back to the reader / router is independent of the data rate, which is set by the synchronization generator 224 and the baud rate generator 248. However, a A person with ordinary skill in the art to which the present invention relates more closely will recognize that the available baud rate range will typically be significantly less than the interrogation frequency (Fi). The baud rate preferably is derived from the interrogation frequency (Fi) of the reader / addrer such as its integer fraction. For example, the baud rate can be set to Fi / 32 (or, in the case of Fe = Fi / 2, the baud rate can be set to Fc / 16). For example, the interrogation frequency (Fi) can be 125 KHz, and the data carrier (Fe) can be set to 62.5 KHz, or half the interrogation frequency. In another example, a polling frequency (Fi) of 13.56 MHz has been found convenient. The data stream such as the exemplary data stream described with respect to Figure 3C is applied by the modulator circuit 246 on the antenna 212, and transmits to the reader / interrogator. It is within the scope of this invention that any convenient modulation scheme is employed including amplitude modulation (AM), frequency modulation (FM), frequency offset encryption (FSK = Frequency Shift Keymg) and phase offset encryption ( P? K = Phase Shift Keymg). However, phase shifted ciphering (PSK) is preferred. AM modulation is not particularly well suited to digital transmission. Frequency modulation schemes such as FM or FSK can be somewhat problematic with respect to propagation of the data modulated transponder output signal through the medium of a tire. OBTAINING A COMPENSATED PRESSURE READING BY TEMPERATURE Figure 4 illustrates a relevant portion of a reader portion of a reader / reader 400. It will be clearly understood that the transponder of the present invention is suitable for use with virtually any conveniently configured reader mutator. The description that follows is limited to extensive architectural functions to be performed in the reader / reader. A person with ordinary skill in the specialty to which he most closely refers to the present invention will be able, from the description herein established, to implement these functions in an interrogator / reader, otherwise "generic". The output signal of the data-modulated transponder is received by antenna 410 (compare 210) of interrogator 400 (compare 200). The received signal is de-modulated and de-encoded in a de-modulator / decoder circuit 420 (DE-MOD / DECODE) in such a way that the different portions of the data stream can be properly segregated from each other. The data referring to temperature and pressure calibration (TEMP COMP PENDIENTS), PRES. COMP, TEMP / PRES.), The temperature count (Nt) and the pressure count (NP) are provided to an arithmetic logic unit 422 capable of generating a temperature compensated signal, real ("Pressure") in a line 423 to display 412 (compare 112) as well as a calibrated temperature signal ("Temperature") on line 423. This information may be displayed to the user either selectively or simultaneously with other relevant information such as the status of the MTMS switch 220, as well as data (DATA) relating to the identification of the tire and the like. While the invention has been described in combination with modalities thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description Accordingly, the invention is intended to encompass all of these alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims

Claims (3)

1. CLAIMS 1. In an integrated circuit (IC) flake, a method for measuring temperature that comprises: circulating a current through a resistor. the resistance value of which is substantially mdependent of the temperature, the current is a function of the absolute temperature of a transistor resident in the IC flake, the transistor is of a type that exhibits a predictable change in its base-emitter voltage over a range of temperature; and reflects the current flowing through the precision resistor to a circuit in the IC flake, the circuit provides an output signal that is proportional to the current flowing through the resistor.
2. 2. The method according to claim 1, characterized in that: the circuit is a relaxation oscillator and the circuit output is a temperature-dependent frequency. The method according to claim 1, characterized in that: the circuit includes at least one internal capacitor; and also comprises selectively switching an external capacitor through the internal capacitor at least to alter a characteristic of the output signal. SUMMARY OF THE INVENTION A temperature detector with a temperature sensitive component (Ql) of a IC flake is implemented which functions as a radio frequency (RF) transponder (200) capable of measuring parameters associated with an object and transmitting data to a external reader / translator (106, 400). In use with a tire (104), the transponder measures the temperature and pressure within the tire. The transponder includes circuits (226) for controlling time windows (Wt and WP) during which real-time temperature and pressure measurements are made and for storing calibration data (236), transponder ID number and the like and for transmitting this information in a data stream (Figure 3C) to the reader / interpreter. An excessive temperature condition can also be detected (MTMS 218) and included in the data stream. The circuits of the transponder are preferably implemented in a single IC flap (204), using CMOS technology with few components external to the IC flake. The transponder is preferably passive, deriving its operational energy from an RF signal that is provided by the external reader / rogue. Data (Nt) indicative of temperature and data (NP) indicative of pressure, both of which are transmitted in the reader / interrogator, together with calibration data. Calibration data stored by the transponder and transmitted in the data stream are a slope of NT / NP, or the "quotient" response of the temperature count divided by the pressure count that is determined during transponder calibration.