Calibration methods and circuits for optimized on-die termination
First Claim
1. An integrated circuit die to communicate data over a plurality of communication channels, the integrated circuit die comprising:
- a. a current source having a plurality of calibration-current output nodes providing a corresponding plurality of calibration currents;
b. a plurality of pads to connect to the communication channels; and
c. a plurality of communication circuits to communicate the data over the communication channels via the pads, each communication circuit including;
i. a first calibration-circuit input node coupled to a respective one of the calibration-current output nodes and receiving one of the calibration currents;
ii. a second calibration-circuit input node coupled to a reference resistor;
iii. a calibration-circuit output port providing a termination-control signal; and
iv. a termination element exhibiting a termination characteristic and including a termination control port coupled to the calibration-circuit output port and receiving the termination-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 transmitter 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 the termination resistances for the signal transmission lines. The ODT control system derives a number of calibration currents from precision voltage and resistance references and distributes the reference currents to a number of transmitters. Each transmitter then derives an ODT calibration signal using the respective reference current and another precision resistor, and then employs the calibration signal to calibrate local termination elements. Distributing calibrated currents provides excellent noise immunity, while limiting the requisite number of external voltage references reduces cost.
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Citations
22 Claims
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1. An integrated circuit die to communicate data over a plurality of communication channels, the integrated circuit die comprising:
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a. a current source having a plurality of calibration-current output nodes providing a corresponding plurality of calibration currents; b. a plurality of pads to connect to the communication channels; and c. a plurality of communication circuits to communicate the data over the communication channels via the pads, each communication circuit including; i. a first calibration-circuit input node coupled to a respective one of the calibration-current output nodes and receiving one of the calibration currents; ii. a second calibration-circuit input node coupled to a reference resistor; iii. a calibration-circuit output port providing a termination-control signal; and iv. a termination element exhibiting a termination characteristic and including a termination control port coupled to the calibration-circuit output port and receiving the termination-control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An integrated circuit comprising:
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a. a current source having a plurality of calibration-current output nodes to provide a corresponding plurality of calibration currents; b. a plurality of reference pads to couple to external reference impedances; c. a plurality of calibration circuits, each calibration circuit coupled to one of the calibration-current output nodes, to receive the corresponding one of the calibration currents, and one of the external reference impedances, wherein each calibration circuit is adapted to derive a termination control signal from the one of the calibration currents and the one external reference impedance; and d. a plurality of termination elements, each termination element including a termination control port coupled to one of the calibration circuits to receive the respective termination control signal. - View Dependent Claims (9, 10)
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11. An integrated circuit comprising:
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a. a plurality of communication circuits, each communication circuit including a termination-calibration circuit; b. a plurality of pads to connect each of the tennination-calibration circuits to respective external reference resistors; and c. a current source having a plurality of calibration-current output nodes, each output node coupled to a respective one of the termination-calibration circuits. - View Dependent Claims (12, 13, 14, 15)
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16. A method of calibrating a plurality of termination elements on an integrated-circuit die, the method comprising:
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a. providing a first calibration current to each of a plurality of communication circuits; and b. for each of the plurality of communication circuits; i. producing a second calibration current proportional to the first calibration current; ii. producing a third calibration current proportional to the first calibration current; iii. drawing the second calibration current through a reference resistor external to the die to develop a first reference voltage; iv. drawing the third calibration current through an adjustable reference on-die-termination (ODT) resistor on the die to develop an ODT voltage; v. comparing the first reference voltage to the ODT voltage; and vi. adjusting at least one of the plurality of termination elements in response to the comparing. - View Dependent Claims (17, 18, 19)
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20. A signal communication system comprising:
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a. a plurality of communication circuits to communicate data over a plurality of communication channels, each communication circuit receiving a supply voltage and including at least one termination element, exhibiting a termination characteristic, and a local reference element; and b. a termination calibration system including; i. means for distributing each of a plurality of calibration currents to respective ones of the communication circuits, wherein each of the calibration currents is independent of temperature and the supply voltage; and ii. means for calibrating the termination characteristic of the at least one termination element in each of the plurality of communication circuits using the respective calibration current to maintain the termination characteristic independent of the temperature and the supply voltage. - View Dependent Claims (21, 22)
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Specification