Calibration methods and circuits to calibrate drive current and termination impedance
First Claim
1. An on-die termination (ODT) control circuit comprising:
- at least one reference-voltage node;
a reference ODT resistor to exhibit a calibrated voltage responsive to an ODT count;
a comparator having a first comparator input, a second comparator input, and a comparator output;
a first pass gate selectively coupling the first comparator input to the at least one reference-voltage node;
a second pass gate selectively coupling the second comparator input to the reference ODT resistor to receive the calibrated voltage;
a third pass gate selectively coupling the second comparator input to the at least one reference-voltage node; and
a counter coupled between the comparator output and the reference ODT resistor, the counter to issue the ODT count responsive to an output of the comparator.
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Accused Products
Abstract
Described are on-die termination (ODT) systems and methods that facilitate high-speed communication between a driver die and a receiver die interconnected via one or more signal transmission lines. An ODT control system in accordance with one embodiment calibrates and maintains termination resistances and drive currents to produce optimal output swing voltages. Comparison circuitry employed to calibrate the reference resistance is also used to calibrate the drive current. Termination elements in some embodiments are divided into two adjustable resistive portions, both of which are designed to minimize capacitive loading. One portion is optimized to produce a relatively high range of adjustment, while the other is optimized for fine-tuning and glitch-free switching.
120 Citations
19 Claims
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1. An on-die termination (ODT) control circuit comprising:
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at least one reference-voltage node; a reference ODT resistor to exhibit a calibrated voltage responsive to an ODT count; a comparator having a first comparator input, a second comparator input, and a comparator output; a first pass gate selectively coupling the first comparator input to the at least one reference-voltage node; a second pass gate selectively coupling the second comparator input to the reference ODT resistor to receive the calibrated voltage; a third pass gate selectively coupling the second comparator input to the at least one reference-voltage node; and a counter coupled between the comparator output and the reference ODT resistor, the counter to issue the ODT count responsive to an output of the comparator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for calibrating a resistance of an on-die termination (ODT) resistor using a single comparator, the method comprising:
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pulling a current from a reference-voltage node through a reference resistor to produce a reference-resistor voltage; applying the reference-resistor voltage to a first input of the comparator; adjusting a second voltage on a second input of the comparator, responsive to an output of the comparator, to set the second voltage equal to the reference-resistor voltage; coupling the ODT resistor to the first input of the comparator; and adjusting the resistance of the ODT resistor, responsive to an output of the comparator, to set a voltage from the ODT resistor equal to the second voltage. - View Dependent Claims (10, 11, 12, 13, 14)
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15. An on-die termination (ODT) control circuit comprising:
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a first reference-voltage node to provide a first reference voltage; a reference ODT resistor to exhibit a calibrated resistance that provides a calibrated voltage responsive to an ODT count; a comparator having a first comparator input coupled to the first reference-voltage node to receive the first reference voltage, a second comparator input, and a comparator output; a multiplexer having a first multiplexer input coupled the reference ODT resistor to receive the calibrated voltage, a second multiplexer input to receive a second reference voltage, and a multiplexer output coupled to the second comparator input; and a counter coupled between the comparator output and the reference ODT resistor, the counter to issue the ODT count responsive to an output of the comparator. - View Dependent Claims (16, 17, 18, 19)
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Specification