Calibration methods and circuits to calibrate drive current and termination impedance
First Claim
1. A termination control circuit comprising:
- a first node to receive a first reference voltage;
a second node to receive a second reference voltage;
an adjustable resistor exhibiting an adjustable impedance responsive to an impedance-control signal;
a comparator having a first input coupled to the first node to receive the first reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output;
a transistor disposed in a path between the second input and a supply terminal, the supply terminal to receive a third reference voltage; and
a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to a signal from the comparator output;
wherein updating the impedance-control signal adjusts the impedance between the second node and the second input of the comparator; and
wherein the transistor selectively disables current flow through the adjustable resistor.
1 Assignment
0 Petitions
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 control circuit comprising:
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a first node to receive a first reference voltage; a second node to receive a second reference voltage; an adjustable resistor exhibiting an adjustable impedance responsive to an impedance-control signal; a comparator having a first input coupled to the first node to receive the first reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output; a transistor disposed in a path between the second input and a supply terminal, the supply terminal to receive a third reference voltage; and a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to a signal from the comparator output; wherein updating the impedance-control signal adjusts the impedance between the second node and the second input of the comparator; and wherein the transistor selectively disables current flow through the adjustable resistor. - View Dependent Claims (2)
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3. A termination control circuit comprising:
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a first node to receive a first reference voltage; a second node to receive a second reference voltage; an adjustable resistor exhibiting an adjustable impedance responsive to an impedance-control signal; a comparator having a first input coupled to the first node to receive the first reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output; a transistor disposed in a path between the second input and a supply terminal, the supply terminal to receive a third reference voltage; and a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to a signal from the comparator output; wherein updating the impedance-control signal adjusts the impedance between the second node and the second input of the comparator, and the counter is operatively coupled between the comparator and the adjustable resistor via a latch, the latch to capture the signal from the comparator output; and a filter, wherein the latch is operatively coupled to the comparator via the filter.
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4. A termination control circuit comprising:
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a first node to receive a first reference voltage; a second node to receive a second reference voltage; an adjustable resistor exhibiting an adjustable impedance responsive to an impedance-control signal; a comparator having a first input coupled to the first node to receive the first reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output; a transistor disposed in a path between the second input and a supply terminal, the supply terminal to receive a third reference voltage; and a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to a signal from the comparator output; wherein updating the impedance-control signal adjusts the impedance between the second node and the second input of the comparator; and wherein the transistor includes a control terminal, and wherein the signal from the comparator output controls a voltage on the control terminal. - View Dependent Claims (5, 6, 7, 8)
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9. A termination control circuit comprising:
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a first node to receive a first reference voltage; a second node to receive a second reference voltage; an adjustable resistor exhibiting an adjustable impedance responsive to an impedance-control signal; a comparator having a first input coupled to the first node to receive the first reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output; a transistor disposed in a path between the second input and a supply terminal, the supply terminal to receive a third reference voltage; and a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to a signal from the comparator output, wherein updating the impedance-control signal adjusts the impedance between the second node and the second input of the comparator; and termination elements coupled to the counter to receive the impedance-control signal; wherein the termination control circuit is instantiated on an integrated circuit device with a receiver circuit including a differential amplifier to receive a pair of complementary signals via respective first and second signal pads, and wherein each of the signal pads is coupled to a DC voltage via a respective one of the termination elements.
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10. 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 and including a first impedance control input; a second termination element, exhibiting a second impedance, coupled to the second node and including a second impedance control input; and a control circuit having; an adjustable reference element to develop a reference impedance; and a feedback path to apply a calibration signal to the adjustable reference element to set the reference impedance; wherein the feedback path is coupled to the first and second impedance control inputs to set the first and second impedances. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification