CURRENT SENSE CASCODE AMPLIFIER
First Claim
1. A current sense amplifier for sensing current through a main switch device of a converter, wherein the main switch device has a current path coupled between an input node and a phase node and has a control input coupled to a control node, said current sense amplifier comprising:
- first and second matching switch devices comprising scaled down versions of the main switch device, each said first and second switch device having a control input coupled to the control node, wherein said first switch device has a current path for coupling between the input node and a first node, and wherein said second switch device has a current path for coupling between the phase node and a second node;
an amplifier control circuit having a current path coupled between said first node and a third node, said amplifier control circuit having an input;
a bias circuit having a current path coupled between said second node and a fourth node and having an output coupled to said input of said amplifier control circuit;
a current generator circuit coupled to said third and fourth nodes which develops a constant first current through said amplifier control circuit and which develops a constant second current through said bias circuit, wherein said second current is about twice said first current; and
a sense circuit having a current path coupled between said first node and ground and having a control input coupled to said third node, wherein said sense circuit develops a sense voltage indicative of current through the current path of the main switch device.
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Accused Products
Abstract
A current sense amplifier sensing current through a main switch of a converter. The amplifier includes first and second switch devices, an amplifier control circuit, a bias circuit, a current generator circuit, and a sense circuit. The main switch is coupled to an input, phase and control nodes. The first and second switch devices are smaller matching versions of the main switch and are both coupled to the main switch and form first and second nodes. The bias circuit is coupled between second and fourth nodes and the amplifier control circuit is coupled between first and third nodes. The current generator develops a first current through the amplifier control circuit and a second current through the bias circuit. The sense circuit has a current path coupled to the first node and is controlled by the third node to develop a sense voltage indicative of current through the main switch.
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Citations
20 Claims
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1. A current sense amplifier for sensing current through a main switch device of a converter, wherein the main switch device has a current path coupled between an input node and a phase node and has a control input coupled to a control node, said current sense amplifier comprising:
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first and second matching switch devices comprising scaled down versions of the main switch device, each said first and second switch device having a control input coupled to the control node, wherein said first switch device has a current path for coupling between the input node and a first node, and wherein said second switch device has a current path for coupling between the phase node and a second node; an amplifier control circuit having a current path coupled between said first node and a third node, said amplifier control circuit having an input; a bias circuit having a current path coupled between said second node and a fourth node and having an output coupled to said input of said amplifier control circuit; a current generator circuit coupled to said third and fourth nodes which develops a constant first current through said amplifier control circuit and which develops a constant second current through said bias circuit, wherein said second current is about twice said first current; and a sense circuit having a current path coupled between said first node and ground and having a control input coupled to said third node, wherein said sense circuit develops a sense voltage indicative of current through the current path of the main switch device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An electronic device, comprising:
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a voltage converter, comprising; a first electronic switch having a current path coupled between an input node and a phase node and having a control input coupled to a first power control node; a second electronic switch having a current path coupled between said phase node and ground and having a control input coupled to a second power control node; and an inductive device coupled between said phase node and an output node; and a controller coupled to said first and second control nodes, said phase node and said input node, said controller including a current sense amplifier comprising; first and second sense devices comprising scaled down versions of said first electronic switch, each said first and second sense device having a control input coupled to said first power control node, wherein said first sense device has a current path coupled between said input node and a first node, and wherein said second sense device has a current path coupled between said phase node and a second node; a bias circuit having a current path coupled between said second node and a fourth node and having an output; an amplifier circuit having a current path coupled between said first node and a third node and having an input coupled to said output of said bias circuit; a current generator circuit coupled to said third and fourth nodes which develops a constant first current through said amplifier control circuit and which develops a constant second current through said bias circuit, wherein said second current is about twice said first current; and a sense circuit having a current path coupled between said first node and ground and having a control input coupled to said third node, wherein said sense circuit develops a sense voltage indicative of current through the current path of the main switch device. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method of sensing current through a main switch device of a voltage converter, wherein the main switch device has a drain coupled to an input node, a source coupled to a phase node and a gate coupled to a control node, said method comprising:
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coupling a gate and a drain of a first switch device to the control node and the input node, respectively, and coupling a source of the first switch device to a first node, wherein the first switch device comprises a scaled down version of the main switch device; coupling a gate of a second switch device to the control node, coupling a drain of the second switch device to the phase node, and coupling a source of the second switch device to a second node, wherein the second switch device matches the first switch device; coupling a current path of an amplifier circuit between the first node and a third node, wherein the amplifier circuit has a control input; coupling a current path of a bias circuit between the second node and a fourth node, and coupling a bias output of the bias circuit to the control input of the amplifier circuit; drawing a constant first current through the amplifier circuit and drawing a constant second current through the bias circuit, wherein the second current is about twice the first current; coupling a resistive device between a fifth node and ground; and coupling a drain of a sense device to the first node, coupling a source of the sense device to the fifth node, and coupling a gate of the sense device to the third node. - View Dependent Claims (20)
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Specification