On-chip termination
AssigneeIntel Corporation
InventorsGregory F. Taylor, Jack A. Price, Chee How Lim
Life of this patent
Estimating the term…
Abstract
Integrated circuits include an impedance control circuit having at least one output terminal coupled to an on-chip reference termination device in order to control output impedance of the reference termination device such that it matches that of an external resistance. The impedance control circuit outputs are also coupled to the on-chip impedance-controlled termination devices which are coupled to each of the external transmission lines to be terminated. In this way, a single reference resistance allows many transmission lines to be properly terminated. The impedance-controlled termination devices are may be implemented as pairs of binary weighted p-channel and n-channel field effect transistors.
Claims20
A circuit comprising:
- a first variable impedance device coupled between a first power supply node and a first node, the first variable impedance device having at least one control terminal;
- a second variable impedance device coupled between the first power supply node and a second node, the second variable impedance device having at least one control terminal;
- a resistive pathway coupled between the second node and ground;
- and
- an impedance control circuit having an input terminal and at least one output terminal, the input terminal of the impedance control circuit coupled to the second node, and the at least one output terminal coupled to the corresponding control terminals of the first and second variable impedance devices and wherein the impedance control circuit comprises a comparator having at least two input terminals;
- a first voltage divider coupled to a first one of the comparator input terminals;
- and a state machine coupled to an output terminal of the comparator.
(Amended) A system, comprising:
- at least one integrated circuit having a plurality of output drivers disposed therein;
- a plurality of electrical conductors, external to the at least one integrated circuit, coupled respectively to the output drivers;
- an integrated circuit having a plurality of variable-impedance termination devices coupled respectively to the plurality of electrical conductors, the variable-impedance termination devices each having a control input;
- and
- an impedance control circuit having an output terminal coupled to the control input terminals of the plurality of variable-impedance termination devices;
- wherein the impedance control circuit comprises a comparator having at least two input terminals;
- a first voltage divider coupled to a first one of the comparator input terminals;
- and a state machine coupled to an output terminal of the comparator.
A system, comprising:
- a first integrated circuit having a plurality of open drain drivers;
- a plurality of bus lines coupled to the plurality of open drain drivers;
- a second integrated circuit having a plurality of receiver circuits, the receiver circuits coupled to the plurality of bus lines;
- and a plurality of impedance-controlled termination devices;
- wherein at least one impedance-controlled termination device is coupled to each of the bus lines and the at least one impedance-controlled termination device is coupled to an impedance control circuit comprising a comparator having at least two input terminals;
- a first voltage divider coupled to a first one of the comparator input terminals;
- and a state machine coupled to an output terminal of the comparator.
A method of providing termination for transmission lines, comprising:
- adjusting the impedance of a plurality of variable-impedance termination devices on a first integrated circuit, based at least in part on the value of a resistive pathway external to the first integrated circuit;
- and
- adjusting the impedance of a plurality of variable-impedance termination devices on a first integrated circuit, based at least in part on variations in temperature, manufacturing tolerances, and power supply voltage.
A method of providing termination for transmission lines, comprising:
- operating a state machine, on a first integrated circuit, to produce at least one control signal indicative of whether to increase or decrease the impedance of a reference impedance termination device based, at least in part, on the value of a resistive pathway;
- and
- adjusting the impedance of a plurality of variable-impedance termination devices on the first integrated circuit.
A method of communicating information between at least two integrated circuits coupled by a bus, the method comprising:
- operating a state machine, on a first integrated circuit, to produce at least one control signal indicative of whether to increase or decrease the impedance of a reference impedance termination device based, at least in part, on the value of a resistive pathway external to the first integrated circuit;
- and
- adjusting the impedance of a plurality of variable-impedance termination devices on the first integrated circuit;
- and
- transmitting information from a second integrated circuit to the first integrated circuit over the bus.
Dependencies are inferred from the claim text.