Calibration methods and circuits for optimized on-die termination
First Claim
1. A termination calibration method for an integrated-circuit die, the method comprising:
- a. drawing a first current through a first reference element, having a first reference impedance, and a reference resistor, having an external-reference resistance, to develop a first termination voltage;
b. comparing, with a comparator, the first termination voltage with a reference voltage to produce a first impedance control signal;
c. adjusting the first reference impedance responsive to the first impedance control signal;
d. drawing a reference drive current through the first reference element and a second reference element, having a second reference impedance, to develop a second termination voltage;
e. comparing, with the comparator, the second termination voltage with the reference voltage to produce a second impedance control signal; and
f. adjusting the second reference impedance responsive to the second impedance control signal.
1 Assignment
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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.
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Citations
21 Claims
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1. A termination calibration method for an integrated-circuit die, the method comprising:
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a. drawing a first current through a first reference element, having a first reference impedance, and a reference resistor, having an external-reference resistance, to develop a first termination voltage; b. comparing, with a comparator, the first termination voltage with a reference voltage to produce a first impedance control signal; c. adjusting the first reference impedance responsive to the first impedance control signal; d. drawing a reference drive current through the first reference element and a second reference element, having a second reference impedance, to develop a second termination voltage; e. comparing, with the comparator, the second termination voltage with the reference voltage to produce a second impedance control signal; and f. adjusting the second reference impedance responsive to the second impedance control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An on-die termination (ODT) calibration method comprising:
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a. drawing a first current through a first impedance and an external reference resistor to develop a first termination voltage between the first impedance and the external reference resistor; b. comparing, with a comparator, the first termination voltage with a reference voltage to produce a first impedance control signal; c. adjusting the first impedance responsive to the first impedance control signal; d. drawing a second current through a second impedance to develop a second termination voltage; e. comparing, with the comparator, the second termination voltage with the reference voltage to produce a second impedance control signal; and f. adjusting the second impedance responsive to the second impedance control signal.
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10. On an integrated-circuit die, an on-die termination control system comprising:
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a. a reference-resistor node to connect to a reference resistor external to the die; b. a comparator having a first comparator input node coupled to the reference-resistor node, a second comparator input node, and a comparator output node; c. a first reference impedance disposed between a reference-voltage node and the second comparator input node and having a first control port coupled to the comparator output node; d. a second reference impedance having a second voltage node and a second control port coupled to the comparator output node; and e. first register bits coupled between the comparator output port and the first reference impedance and second register bits coupled between the comparator output port and the second reference impedance. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. On an integrated-circuit die, an on-die termination control system comprising:
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a reference node to connect to a reference resistor external to the die; a comparator having a first comparator input node coupled to the reference node, a second comparator input node, and a comparator output node; a first reference impedance disposed between a reference-voltage node and the second comparator input node and having a first control port coupled to the comparator output node; a second reference impedance having a second control port coupled to the comparator output node; and a first counter coupled between the comparator output node and the first reference impedance and a second counter coupled between the comparator output node and the second reference impedance.
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20. A termination calibration method for an integrated-circuit die, the method comprising;
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drawing a first current through a first reference element, having a first reference impedance, and a reference resistor, having an external-reference resistance, to develop a first termination voltage; comparing, with a comparator, the first termination voltage with a reference voltage to produce a first impedance control signal; adjusting the first reference impedance responsive to the first impedance control signal until the first termination voltage is the reference voltage; drawing a reference drive current through the first reference element and a second reference element, having a second reference impedance, to develop a second termination voltage; comparing, with the comparator, the second termination voltage with the reference voltage to produce a second impedance control signal; and adjusting the second reference impedance responsive to the second impedance control signal until the second termination voltage is the reference voltage. - View Dependent Claims (21)
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Specification