Calibration methods and circuits to calibrate drive current and termination impedance
First Claim
1. An integrated circuit device comprising:
- a receiver circuit including a differential amplifier to receive a pair of complementary input signals via respective first and second nodes;
a first termination element, exhibiting a first impedance, coupled to the first node;
a second termination element, exhibiting a second impedance, coupled to the second node; and
a control circuit to set a termination value for each of the first and second termination elements, the control circuit comprising;
a digitally adjustable termination element exhibiting a third impedance;
a comparator having first and second inputs, the first input to receive a reference voltage and the second input to receive a voltage developed by drawing a first current through the digitally adjustable termination element; and
a first counter circuit to provide a first digital value that is updated based on an output of the comparator, wherein the first digital value is used to set the first, second, and third impedances.
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.
116 Citations
28 Claims
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1. An integrated circuit device comprising:
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a receiver circuit including a differential amplifier to receive a pair of complementary input signals via respective first and second nodes; a first termination element, exhibiting a first impedance, coupled to the first node; a second termination element, exhibiting a second impedance, coupled to the second node; and a control circuit to set a termination value for each of the first and second termination elements, the control circuit comprising; a digitally adjustable termination element exhibiting a third impedance; a comparator having first and second inputs, the first input to receive a reference voltage and the second input to receive a voltage developed by drawing a first current through the digitally adjustable termination element; and a first counter circuit to provide a first digital value that is updated based on an output of the comparator, wherein the first digital value is used to set the first, second, and third impedances. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for terminating a differential signal channel, the method comprising:
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receiving first and second complementary input signals at respective first and second pads; terminating the first and second pads of the differential signal channel with respective first and second termination elements exhibiting respective first and second termination impedances; drawing a current through a digitally adjustable reference resistor to obtain a reference-resistor voltage; comparing the reference-resistor voltage with a reference voltage; updating a digital value stored in a counter based on the comparing; and adjusting the digitally adjustable reference resistor and the first and second termination impedances in response to the digital value. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. An integrated circuit device comprising:
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a plurality of receiver circuits, each receiver circuit of the plurality of receiver circuits including; a differential amplifier to receive a pair of complementary input signals via respective first and second input nodes; a first termination element, exhibiting a first impedance, coupled to the respective first input node of each receiver circuit; and a second termination element, exhibiting a second impedance, coupled to the respective second input node of each receiver circuit; and a control circuit to set a termination value for each of the first and second termination elements, the control circuit comprising; a digitally adjustable termination element exhibiting a third impedance; a comparator having first and second inputs, the first input to receive a reference voltage and the second input to receive a second voltage developed by drawing a current through the digitally adjustable termination element; and a counter circuit to provide a digital value that is updated based on an output of the comparator, wherein the digital value is used to set the first and second impedances of each respective receiver circuit, and the third impedance. - View Dependent Claims (24, 25, 26, 27, 28)
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Specification