Sensor threshold circuit
First Claim
1. A sensor threshold circuit that outputs a digital signal with a hysteresis characteristic, in receipt of an input from a sensor, the sensor threshold circuit comprising:
- a voltage comparator that digitizes an output voltage of the sensor;
a sensor drive current detecting circuit that detects a sensor drive current;
a sensor bias current generating circuit that generates a threshold current, wherein the magnitude of the threshold current is 1/K (where K>
0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, and wherein the threshold current is based upon the output from the voltage comparator;
a threshold adjusting current generating circuit that generates a threshold adjusting current wherein the magnitude of the threshold adjusting current is 1/A (where A>
0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, wherein the threshold adjusting current generating circuit adds or subtracts the threshold adjusting current to or from the threshold current that has been generated by the sensor bias current generating circuit to generate a sensor bias current, and wherein the threshold adjusting current generating circuit supplies the sensor bias current to an output terminal of the sensor.
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Accused Products
Abstract
There is provided a sensor threshold circuit that makes available a hysteresis width that is not dependent on the change in a threshold point. Since a bias current IB is generated by a threshold current IT and a threshold adjusting current ICONT, the threshold point is given by a coefficient A and a coefficient K and the hysteresis width |BH| is given by the coefficient K. Accordingly, when the coefficient K is determined, the hysteresis width |BH| is not dependent on the coefficient A and keeps a constant value. In addition, since the coefficient A depends on the resistance ratio, the threshold point is variable by changing a single resistor. Further, when the coefficient K is determined, the hysteresis width |BH| is also determined to be a single value with no variations in its value, no changes according to temperature, and no changes over time.
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Citations
8 Claims
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1. A sensor threshold circuit that outputs a digital signal with a hysteresis characteristic, in receipt of an input from a sensor, the sensor threshold circuit comprising:
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a voltage comparator that digitizes an output voltage of the sensor; a sensor drive current detecting circuit that detects a sensor drive current; a sensor bias current generating circuit that generates a threshold current, wherein the magnitude of the threshold current is 1/K (where K>
0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, and wherein the threshold current is based upon the output from the voltage comparator;a threshold adjusting current generating circuit that generates a threshold adjusting current wherein the magnitude of the threshold adjusting current is 1/A (where A>
0) times the magnitude of the sensor drive current that has been detected by the sensor drive current detecting circuit, wherein the threshold adjusting current generating circuit adds or subtracts the threshold adjusting current to or from the threshold current that has been generated by the sensor bias current generating circuit to generate a sensor bias current, and wherein the threshold adjusting current generating circuit supplies the sensor bias current to an output terminal of the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification