Systems and methods for sensing current through a low-side field effect transistor
First Claim
1. An apparatus comprising:
- a switching circuit coupled to a load and a reference node, the switching circuit capable of conducting a reverse current from the reference node to the load when a voltage at the load is lower than a voltage at the reference node;
a voltage source having a first terminal coupled to the load, a second terminal configured to follow a voltage at the load, and produce a voltage indicative of a voltage drop across the switching circuit; and
a comparator circuit coupled to compare a voltage at the second terminal of the voltage source to the voltage at the reference node and configured to indicate when the reverse current has a magnitude greater than a predetermined threshold.
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Accused Products
Abstract
Systems and techniques detecting a reverse current are disclosed. An apparatus comprises a switching circuit coupled to a load and a reference node. The switching circuit may be capable of conducting a reverse current from the reference node to the load when a voltage at the load is lower than a voltage at the reference node. A voltage source has a first terminal coupled to the load, a second terminal configured to follow a voltage at the load, and produces a voltage proportional to a voltage drop across the switching circuit. A comparator circuit is coupled to compare a voltage at the second terminal of the voltage source to the voltage at the reference node and configured to indicate when the reverse current has a magnitude greater than a predetermined threshold.
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Citations
32 Claims
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1. An apparatus comprising:
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a switching circuit coupled to a load and a reference node, the switching circuit capable of conducting a reverse current from the reference node to the load when a voltage at the load is lower than a voltage at the reference node; a voltage source having a first terminal coupled to the load, a second terminal configured to follow a voltage at the load, and produce a voltage indicative of a voltage drop across the switching circuit; and a comparator circuit coupled to compare a voltage at the second terminal of the voltage source to the voltage at the reference node and configured to indicate when the reverse current has a magnitude greater than a predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 18)
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- 6. The apparatus of 1 wherein the voltage source comprises a sense transistor and a current source coupled to a source terminal of the sense transistor.
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19. A motor driver circuit comprising:
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a low-side transistor coupled between a load and a reference node, the low-side transistor capable of conducting a reverse current from the reference node to the load when a voltage at the load is lower than a voltage at the reference node; a voltage source having a first terminal coupled to the load, a second terminal configured to follow a voltage at the load, and produce a voltage indicative of a voltage drop across a body diode of the low-side transistor; and a comparator circuit coupled to compare a voltage at the second terminal of the voltage source to the voltage at the reference node and configured to indicate when the reverse current is flowing. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A motor driver circuit comprising:
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a motor; and a switched bridge for driving the motor, the switched bridge comprising; a low-side transistor having a gate terminal coupled to a control circuit, a drain terminal coupled to at least one coil of the motor, and a source terminal coupled to a reference node; a sense transistor having a gate terminal coupled to the gate terminal of the low-side transistor, a drain terminal coupled to the at least one coil of the motor, and a source terminal; a current source coupled to the source terminal of the sense transistor to produce a voltage across a body diode of the sense transistor and to allow a voltage at the source terminal of the sense transistor to follow a voltage at the at least one coil of the motor, wherein the source terminal of the sense transistor is configured to produce a voltage indicative of a voltage drop across a body diode of the low-side transistor; and a comparator circuit coupled to compare the voltage at the source terminal of the sense transistor to a voltage at the reference node and to indicate when a predetermined reverse current is flowing from the reference node to the at least one coil of the motor through the low-side transistor by indicating when the voltage at the source terminal of the sense transistor is less than the voltage at the reference node. - View Dependent Claims (27, 28, 29)
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30. A method comprising:
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generating, by a voltage source, a voltage that is indicative of a voltage drop across a switching circuit that is coupled to a load and a reference node; allowing at least one terminal of the voltage source to follow a voltage at the load; and indicating whether a predetermined reverse current is flowing through the switching circuit by comparing a voltage at the one terminal of the voltage source to a voltage at the reference node. - View Dependent Claims (31, 32)
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Specification