SENSOR NODE VOLTAGE CLAMPING CIRCUIT AND METHOD
First Claim
1. A voltage clamping circuit comprising:
- a current source comprising a fixed current source and a variable current source;
a variable resistor receiving current from the current source, the variable resistor operable to vary its resistance in response to an environmental operating condition for the variable resistor;
an amplifier configured to compare a sensor node voltage, the sensor node voltage in communication with a voltage drop across the variable resistor, to a reference voltage, the amplifier configured and connected to provide a control output received by the variable current source to modify a current output from the variable current source to at least in part prevent the sensor node voltage from crossing a second reference voltage.
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Abstract
A voltage clamping circuit includes a current source having a fixed current source and a variable current source and a variable resistor receiving current from the current source. The variable resistor varies its resistance in response to an environmental operating condition. The voltage clamping circuit also includes an amplifier configured to compare a sensor node voltage with a reference voltage, the sensor node voltage being in communication with the voltage drop across the variable resistor. The amplifier is configured and connected to provide a control output to control the variable current source to modify current output from the variable current source to at least in part prevent the sensor node voltage from exceeding a reference voltage when certain operating conditions are present.
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Citations
11 Claims
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1. A voltage clamping circuit comprising:
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a current source comprising a fixed current source and a variable current source; a variable resistor receiving current from the current source, the variable resistor operable to vary its resistance in response to an environmental operating condition for the variable resistor; an amplifier configured to compare a sensor node voltage, the sensor node voltage in communication with a voltage drop across the variable resistor, to a reference voltage, the amplifier configured and connected to provide a control output received by the variable current source to modify a current output from the variable current source to at least in part prevent the sensor node voltage from crossing a second reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for clamping a sensor node voltage to avoid false signals of an open circuit comprising:
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providing a current to a sensor node such that the current flows through a variable resistor; sensing the sensor node voltage to determine whether the sensor node voltage exceeds a low reference voltage; providing a first signal when the sensor node voltage exceeds the low reference voltage; sensing voltage at the sensor node to determine whether the sensor node voltage exceeds a middle reference voltage; adjusting the current when the sensor node voltage exceeds the middle reference voltage to clamp the sensor node voltage to the middle reference voltage; sensing the sensor node voltage to determine whether the sensor node voltage exceeds a high reference voltage; providing a second signal when the sensor node voltage exceeds the high reference voltage indicating that the variable resistor has been removed. - View Dependent Claims (10)
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11. A voltage clamping circuit comprising:
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a current source comprising a fixed current source and a variable current source; a variable resistor receiving current from the current source, the variable resistor operable to vary its resistance in response to an environmental operating condition for the variable resistor; an amplifier configured to compare a sensor node voltage, the sensor node voltage in communication with a voltage drop across the variable resistor, to a reference voltage, the amplifier configured and connected to provide a control output received by the variable current source to modify a current output from the variable current source to at least in part prevent the sensor node voltage from crossing a second reference voltage; a first comparator configured to compare the sensor node voltage in communication with the voltage drop across the variable resistor to a first reference voltage indicative of the environmental operating condition for the variable resistor; a second comparator configured to compare the sensor node voltage in communication with the voltage drop across the variable resistor to the second reference voltage indicative of the environmental operating condition for the variable resistor; and a digital element configured to accept a first comparator output from the first comparator and a second comparator output from the second comparator and to provide a first output signal when the first comparator output and the second comparator output indicate that the sensor node voltage has predetermined relationships relative to the first reference voltage and the second reference voltage.
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Specification