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 reference voltage;
a second node to couple to a reference resistance;
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 reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output;
a transistor coupled between the second input and a supply terminal; and
a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to an output from 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.
104 Citations
24 Claims
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1. A termination control circuit comprising:
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a first node to receive a reference voltage; a second node to couple to a reference resistance; 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 reference voltage, a second input coupled to the second node via the adjustable resistor, and a comparator output; a transistor coupled between the second input and a supply terminal; and a counter operatively coupled between the comparator output and the adjustable resistor, the counter to update the impedance-control signal responsive to an output from the comparator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. 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 (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification