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US 8,138,822 B1Granted
Circuits and methods for calibrating switching current sources
AssigneeMarvell International Ltd.
InventorSasan Cyrusian
Life of this patent
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Abstract
In one embodiment the present invention includes circuits and methods for calibrating switching current sources. A difference between a source current and a sink current is detected during a calibration phase. The difference is used to generate a digital signal to adjust a programmable current source to reduce the difference between currents. In one embodiment, a binary search is used to generate the digital signal during an initial calibration phase, and a linear approximation is used to generate the digital signal during an operational calibration phase.
Claims20
A circuit comprising:
- a first current source;
- a first switch having
- a first terminal coupled to an output of the first current source, and
- a second terminal coupled to an output node;
- a second current source;
- a second switch having
- a first terminal coupled to an output of the second current source, and
- a second terminal coupled to the output node;
- a third switch configured to open and close in response to a calibration signal, the third switch having
- a first terminal coupled to the output of the first current source, and
- a second terminal coupled to a first node;
- a fourth switch configured to open and close in response to the calibration signal, the fourth switch having
- a first terminal coupled to the output of the second current source, and
- a second terminal coupled to the first node;
- and
- a programmable current source having an output coupled to the first current source or the second current source,
- wherein the calibration signal closes the third switch and the fourth switch in response to both the first switch and the second switch being open, and
- wherein the programmable current source is adjusted using a digital signal to reduce a difference between a first current from the first current source into the first node and a second current into the second current source out of the first node, wherein the digital signal is generated using a digital algorithm based on said difference.
15 more elements
A method comprising:
- detecting a first signal, the first signal opening and closing a first switch, the first switch having a first terminal coupled to an output of a first current source and a second terminal coupled to an output node;
- detecting a second signal, the second signal opening and closing a second switch, second switch having a first terminal coupled to an output of a second current source and a second terminal coupled to the output node;
- closing a third switch and a fourth switch when both the first and second switches are open, the third switch having a first terminal coupled to the output of the first current source and a second terminal coupled to a first node and the fourth switch having a first terminal coupled to the output of the second current source and a second terminal coupled to the first node;
- detecting a difference between a first current from the first current source into the first node and a second current into the second current source out of the first node;
- and
- adjusting a programmable current source using a digital signal to reduce the difference, the programmable current source having an output coupled to the first current source or the second current source,
- wherein the digital signal is generated using a digital algorithm based on said difference.
4 more elements
Dependencies are inferred from the claim text.