Asymmetric voltage monitor for series supplies
First Claim
1. A monitor circuit for use with dual voltage sources for providing an indication of an imbalance therebetween, comprising:
- a common connection for electrically connecting the voltage sources together;
a voltage divider connected between the voltage sources, said voltage divider having an output which changes with respect to said common connection when the voltage of the sources changes asymmetrically;
a sensor transistor connected to said common connection and to said voltage divider output for generating an output current in response to a voltage difference between said common connection and said output of said voltage divider;
a further transistor responsive to current flow through said divider for producing a further output current; and
an output circuit for subtracting said output current of said sensor transistor from said output current of said further transistor to provide a monitor output logic signal indicative of said imbalance.
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Accused Products
Abstract
Disclosed is a supply voltage monitor for detecting the asymmetric decay of one voltage source (Vdd) with respect to another voltage source (Vss). The monitor circuit (24) includes a resistive voltage divider (26) having a plurality of voltage tap positions (32,35,38). A sensor transistor (40) monitors the voltage between a common connection (16) connecting the voltage sources and the voltage at a desired tap position (38) of the divider network (26). On detecting an imbalance between the voltage sources (Vdd, Vss), the sensor transistor (40) drives a current mirror circuit (42). The current mirror circuit (42) defines an output (50) of the monitor circuit (24), together with a reference transistor (48) biased by a voltage of the divider network (26).
12 Citations
39 Claims
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1. A monitor circuit for use with dual voltage sources for providing an indication of an imbalance therebetween, comprising:
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a common connection for electrically connecting the voltage sources together; a voltage divider connected between the voltage sources, said voltage divider having an output which changes with respect to said common connection when the voltage of the sources changes asymmetrically; a sensor transistor connected to said common connection and to said voltage divider output for generating an output current in response to a voltage difference between said common connection and said output of said voltage divider; a further transistor responsive to current flow through said divider for producing a further output current; and an output circuit for subtracting said output current of said sensor transistor from said output current of said further transistor to provide a monitor output logic signal indicative of said imbalance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A monitor circuit for use with a dual voltage source for providing an indication of an imbalance therebetween, comprising:
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a resistive strip connected between said sources for defining a continuum of different voltages along said strip; a plurality of taps connected to said strip; a sensor transistor with a first electrode connected to a common connection said voltage sources and having a second electrode connected to one of said voltage taps;
a first transistor and a second transistor defining a current mirror connected to said sensor transistor, one transistor of said mirror being connected to an output of said monitor and to one of said voltage sources; andan output transistor connected to said monitor output and to the other of said voltage sources, said output transistor being connected to one of said taps for biasing said output transistor. - View Dependent Claims (11, 12, 13, 14)
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15. A monitor circuit for use with dual voltage sources for providing an indication of an imbalance therebetween, comprising:
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a voltage divider connected between the voltage sources, said voltage divider having at least first, second and third taps each providing a different output voltage of said divider; a current source coupled to said first tap for providing a reference output current representative of voltage across said divider; a sensor responsive to a voltage difference between a common connection of the voltage sources and said voltage divider for providing a sensor output current; means for selectively connecting said sensor to said second tap for making said monitor circuit responsive to an asymmetrical imbalance of one of said voltage sources with respect to the other of said voltage sources, and for selectively connecting said sensor to said third tap for making said monitor responsive to an asymmetrical imbalance of said other voltage source with respect to said one voltage source; and an output circuit for subtracting said sensor output current from said reference output current for providing a digital representation of said imbalance. - View Dependent Claims (16, 17, 18, 19)
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20. A method of sensing the asymmetrical imbalance of a pair of voltages to be monitored comprising the steps of:
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providing a continuum of voltages with magnitudes between the magnitudes of the monitored voltages, such that when one of the monitored voltages changes, said continuum of voltages changes; generating a first output current in proportion to said continuum of voltages; sensing a voltage change between a selected one of said continuum of voltages and a voltage defined by a common connection between said voltage sources; generating a second output current in response to said sensed voltage change; and subtracting said second current from said first current for generating a digital output representation of the asymmetric operation of said monitored voltages. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 32)
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29. A method of fabricating a universal voltage monitor circuit for monitoring the relative magnitudes of first and second input voltages, comprising the steps of:
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forming a divider having end points for receiving respective ones of said input voltages and having at least first, second and third taps providing respective tap voltages; forming a current source responsive to a voltage produced at said first tap for providing a reference current; forming a voltage sensor circuit responsive to a voltage difference between a predefined stable voltage and one of said first and second tap voltages so as to provide an output current indicative of asymmetrical operation of the voltages connected between said end points of the divider; forming a combining circuit for subtracting said output current of said voltage sensor from said reference current; and providing the option of connecting a given input node of the sensor circuit to one of said second and third taps of said divider to detect asymmetric operation of the one monitored voltage with respect to the other monitored voltage, and the option of connecting said given input node of the sensor circuit to another one of said second and third taps of said divider to detect the asymmetric operation of the other said monitored voltage with respect to the said one monitored voltage. - View Dependent Claims (30, 31, 33)
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34. A method of sensing an asymmetrical operation of a pair of voltages, comprising the steps of:
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connecting the pair of voltages across a divider having a plurality of tap positions each providing a voltage which changes when at least one voltage of said pair of voltages changes in magnitude; converting a voltage of one of said tap positions to a reference output current which changes in response to a change in one voltage of said pair of voltages, said reference current providing an output indication of current flow through said divider; sensing a predetermined voltage difference between said common voltage and a voltage of another of said tap positions to provide a trip indication of asymmetrical operation of said pair of voltages; and converting said trip indication into an output current which is subtractive from said reference current to thereby provide an output indication of asymmetric operation of said pair of voltages. - View Dependent Claims (35, 36, 37)
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38. A voltage monitor circuit, comprising:
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a voltage divider to which first and second input voltages to be monitored are applied; a first sensor coupled to a first fixed tap on said divider for providing an output current representative of current flow through said divider; a second sensor coupled to a second fixed tap on said divider for providing an output representative of the relative magnitude of said input voltages; and an output circuit coupled to said sensors for subtracting said output current of said second sensor from said output current of said first sensor to provide an output logic signal having a first level when the magnitude of said first input voltage exceeds that of said second input voltage by a threshold value and having a second level otherwise.
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39. A voltage monitor circuit, comprising:
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a potential divider having a pair of taps; first and second transistors, each having a control electrode coupled to a respective one of said pair of taps, said first transistor providing an output current proportional to a current flow through said divider, said second transistor providing an output current indicative of the relative magnitudes of first and second potentials applied to end points of said divider; and a current mirror having an input terminal connected to receive said output current of said second transistor and having an output terminal connected to receive said output current of said first transistor, said output terminal providing a logic signal indicative of said relative magnitudes of said potentials.
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Specification