Calibration methods and circuits to calibrate drive current and termination impedance
First Claim
1. A method for calibrating a resistance of an on-die termination (ODT) resistor against an off-die resistor using a single comparator, the method comprising:
- drawing a reference-resistor current through the off-die resistor to develop a reference-resistor voltage;
comparing, with the single comparator, the reference-resistor voltage to a reference voltage;
adjusting the reference-resistor current through the off-die resistor responsive to an output of the single comparator until the reference-resistor voltage matches the reference voltage to produce a calibrated reference-resistor current and a calibrated reference-resistor voltage;
creating a calibrated ODT current proportional to the calibrated reference-resistor current;
drawing the calibrated ODT current through the ODT resistor to develop an ODT voltage;
adjusting the resistance of the ODT resistor responsive to the output of the single comparator until the ODT voltage matches the calibrated reference-resistor voltage and the reference voltage; and
second comparing, with the single comparator, the ODT voltage to the calibrated reference-resistor voltage.
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.
124 Citations
20 Claims
-
1. A method for calibrating a resistance of an on-die termination (ODT) resistor against an off-die resistor using a single comparator, the method comprising:
-
drawing a reference-resistor current through the off-die resistor to develop a reference-resistor voltage; comparing, with the single comparator, the reference-resistor voltage to a reference voltage; adjusting the reference-resistor current through the off-die resistor responsive to an output of the single comparator until the reference-resistor voltage matches the reference voltage to produce a calibrated reference-resistor current and a calibrated reference-resistor voltage; creating a calibrated ODT current proportional to the calibrated reference-resistor current; drawing the calibrated ODT current through the ODT resistor to develop an ODT voltage; adjusting the resistance of the ODT resistor responsive to the output of the single comparator until the ODT voltage matches the calibrated reference-resistor voltage and the reference voltage; and second comparing, with the single comparator, the ODT voltage to the calibrated reference-resistor voltage. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A method for calibrating a resistance of an on-die termination (ODT) resistor against an off-die resistor using a single comparator, the method comprising:
-
drawing a reference-resistor current through the off-die resistor to develop a reference-resistor voltage; comparing, with the single comparator, the reference-resistor voltage to a reference voltage; adjusting the reference-resistor current through the off-die resistor responsive to an output of the single comparator until the reference-resistor voltage matches the reference voltage to produce a calibrated reference-resistor current and a calibrated reference-resistor voltage; creating a calibrated ODT current proportional to the calibrated reference-resistor current; and drawing the calibrated ODT current through the ODT resistor to develop an ODT voltage; and
adjusting the resistance of the ODT resistor responsive to the output of the single comparator until the ODT voltage matches the calibrated reference-resistor voltage and the reference voltage;wherein the creating the calibrated ODT current comprises mirroring the calibrated reference-resistor current. - View Dependent Claims (7)
-
-
8. An on-die termination (ODT) control circuit comprising:
-
a comparator having; a first comparator input; a second comparator input; and a comparator output; a multiplexer having; a first multiplexer input; a second multiplexer input; and a multiplexer output coupled to the second comparator input; an adjustable ODT element having; a first current-handling terminal; a second current-handling terminal coupled to the second multiplexer input; and an ODT control input; and circuitry coupled between the comparator output and the ODT control input of the adjustable ODT element, the circuitry to provide a digital value to the ODT control input to calibrate an impedance through the adjustable ODT element. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
-
Specification