US 6,445,245 B1 · Digitally controlled impedance for I/O of an integrated circuit device

Abstract

A system for controlling the impedances of circuits on an integrated circuit chip is provided. At least one circuit is selected to operate as a p-channel reference circuit, and at least one circuit is selected to operate as an n-channel reference circuit. Other circuits are selected to operate as circuits and/or line termination circuits. A digitally controlled impedance (DCI) circuit controls the p-channel reference circuit to determine a desired configuration of p-channel transistors for use in the circuits. The DCI circuit further controls the n-channel reference circuit to determine a desired configuration of n-channel transistors for use in the circuits. The DCI circuit takes into account such factors as resistances of p-channel transistors in the p-channel reference circuit, resistances of n-channel transistors in the n-channel reference circuit, as well as temperature, voltage and process variations. The DCI circuit relays information identifying the desired configurations of the n-channel and p-channel transistors to the circuits. The circuits are then configured in response to this information.

Claims14

Dependent claims

A system for controlling the impedance of circuits on an integrated circuit, the system comprising:

a first circuit that includes:
a first pad;
a first set of transistors coupled in parallel between a first terminal and the first pad;
a first resistor coupled between the first pad and a second terminal;
a first reference voltage circuit for generating a first reference voltage, the first reference voltage being selected, in response to a first control signal, from one of a first plurality of reference voltages;
a first comparator coupled to receive a pad voltage from the first pad and one of the first plurality of reference voltages generated by the first reference voltage circuit;
and
a first control circuit coupled to receive a second control signal from the first comparator, and in response, turn on a subset of the first set of transistors, such that an on-resistance of the subset of the first set of transistors has a first numerical relationship with a resistance of the first resistor, the first relationship being controllable by the first control signal.

5 more elements

A system for controlling the impedance of circuits on an integrated circuit, the system comprising:

a first circuit that includes:
a first pad;
a first set of transistors coupled in parallel between a first terminal and the first pad;
a first resistor coupled between the first pad and a second terminal;
a first reference voltage circuit for generating a first reference voltage, the first reference voltage being selected, in response to a first control signal, from one of a first plurality of reference voltages;
a first comparator coupled to receive a pad voltage from the first pad and one of the first plurality of reference voltages generated by the first reference voltage circuit;
and
a first control circuit coupled to receive a second control signal from the first comparator, and in response, turn on a subset of the first set of transistors, such that an on-resistance of the subset of the first set of transistors has a first numerical relationship with a resistance of the first resistor, the first relationship being controllable by the first control signal;
and
a second circuit that includes:
a second pad;
a second set of transistors coupled in parallel between the second terminal and the second pad;
a second resistor coupled between the second pad and the first terminal;
a second reference voltage generator controlled by the first control signal to generate a second reference voltage, the second reference voltage being selected from one of a second plurality of reference voltages;
a second comparator coupled to receive a pad voltage from the second pad and the second reference voltage;
and
a second control circuit coupled to receive a third control signal from the second comparator, and in response, turn on a subset of the second set of transistors, such that an on-resistance of the subset of the second set of transistors has a second numerical relationship with a resistance of the second resistor, the second numerical relationship being controllable by the first control signal.

14 more elements

Dependencies are inferred from the claim text.

Digitally controlled impedance for I/O of an integrated circuit device

Life of this patent

Digitally controlled impedance for I/O of an integrated circuit device

Life of this patent

Abstract

Claims14