Advanced thermal sensor
First Claim
1. A thermal sensing system comprising:
- a reference voltage generator configured to generate a non-constant first reference voltage that varies as a known first function of temperature;
a thermal sensor configured to generate a sensor voltage that varies as a known second function of temperature, wherein the second function intersects the first function; and
a first comparator configured toreceive the sensor voltage and the first reference voltage,compare the sensor voltage and the first reference voltage, andgenerate a first comparison output signal based on the comparison of the sensor voltage and the first reference voltage;
wherein the thermal sensor and the reference voltage generator are integrated into a single circuit that includesan operational amplifier,first, second and third transistors,first and second PN junctions, wherein the second PN junction has a cross-sectional area greater than a cross-sectional area of the first PN junction, andfirst and second resistors,wherein the source of each of the transistors is tied together and connected to a voltage source,wherein the gate of each of the transistors is tied together and connected to an output of the operational amplifier,wherein the drain of the first transistor is coupled to an inverting input of the operational amplifier and the drain of the second transistor is coupled to a non-inverting input of the operational amplifier,wherein the first PN junction is coupled between the drain of the first transistor and ground,wherein the first resistor and the first PN junction are coupled in series between the drain of the second transistor and ground,wherein the second resistor is coupled between the drain of the third transistor and ground, andwherein the first reference voltage comprises a voltage at the drain of the third transistor.
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Accused Products
Abstract
Systems and methods for reducing the complexity and size of thermal sensors, where the voltage of a thermally sensitive device is compared to a reference voltage that varies as a function of temperature, rather than being constant. One embodiment comprises a thermal sensing system including a reference voltage generator, a thermal sensor and a comparator. The reference voltage generator is configured to generate a non-constant reference voltage that varies as a known function of temperature. The thermal sensor is configured to generate a sensor voltage that also varies as a known function of temperature. The functions of the reference and sensor voltages cross at a known temperature/voltage. The comparator is configured to compare the sensor voltage and the reference voltage and to generate a comparison output signal based on the comparison of the sensor voltage and the first reference voltage. A transition in this signal indicates the reference temperature.
56 Citations
18 Claims
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1. A thermal sensing system comprising:
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a reference voltage generator configured to generate a non-constant first reference voltage that varies as a known first function of temperature; a thermal sensor configured to generate a sensor voltage that varies as a known second function of temperature, wherein the second function intersects the first function; and a first comparator configured to receive the sensor voltage and the first reference voltage, compare the sensor voltage and the first reference voltage, and generate a first comparison output signal based on the comparison of the sensor voltage and the first reference voltage; wherein the thermal sensor and the reference voltage generator are integrated into a single circuit that includes an operational amplifier, first, second and third transistors, first and second PN junctions, wherein the second PN junction has a cross-sectional area greater than a cross-sectional area of the first PN junction, and first and second resistors, wherein the source of each of the transistors is tied together and connected to a voltage source, wherein the gate of each of the transistors is tied together and connected to an output of the operational amplifier, wherein the drain of the first transistor is coupled to an inverting input of the operational amplifier and the drain of the second transistor is coupled to a non-inverting input of the operational amplifier, wherein the first PN junction is coupled between the drain of the first transistor and ground, wherein the first resistor and the first PN junction are coupled in series between the drain of the second transistor and ground, wherein the second resistor is coupled between the drain of the third transistor and ground, and wherein the first reference voltage comprises a voltage at the drain of the third transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A thermal sensing system comprising:
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a reference voltage generator configured to generate a non-constant first reference voltage that varies as a known first function of temperature and a non-constant second reference voltage that varies as a known second function of temperature; a thermal sensor configured to generate a sensor voltage that varies as a known third function of temperature, wherein the third function intersects the first function and the second function; a first comparator configured to receive the sensor voltage and the first reference voltage, compare the sensor voltage and the first reference voltage, and generate a first comparison output signal based on the comparison of the sensor voltage and the first reference voltage; and a second comparator configured to receive the sensor voltage and the second reference voltage, compare the sensor voltage and the second reference voltage, and generate a second comparison output signal based on the comparison of the sensor voltage and the second reference voltage. - View Dependent Claims (10, 11)
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12. A method comprising:
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providing a reference voltage source which provides a first reference voltage that increases as a known first function of temperature and is insensitive to manufacturing variations and a second reference voltage that increases as a known third function of temperature and is insensitive to manufacturing variations; providing a thermal sensor which provides a sensor voltage that decreases as a known second function of temperature and is insensitive to manufacturing variations; comparing the sensor voltage to the first reference voltage; generating a first temperature indicator signal that is not asserted when the sensor voltage is less than the first reference voltage and is asserted when the sensor voltage is greater than the first reference voltages; comparing the sensor voltage to the second reference voltage; and generating a second temperature indicator signal that is asserted when the sensor voltage is less than the second reference voltage and is not asserted when the sensor voltage is greater than the second reference voltage. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification