Apparatus and method to provide a single reference component for multiple circuit compensation using digital impedance code shifting

An apparatus, comprising:

• a single external resistor having a resistance;
• a first plurality of transistors coupled to the single external resistor;
• a control circuit coupled to the first plurality of transistors, the control circuit capable to produce a reference resistance code corresponding to a substantial match of the resistance of the single external resistor based on a number of activated transistors in the first plurality of transistors;
• and
• at least a second plurality of transistors coupled to the control circuit, the control circuit capable to activate or deactivate at least one transistor in the second plurality of transistors based on the reference resistance code to generate a resistance associated with a circuit attribute different from a circuit attribute associated with the first plurality of transistors.

A system, comprising:

• a single external resistor having a resistance and mounted on a motherboard;
• a first plurality of transistors on a chip and coupled to the single external resistor by a pad or pin, the first plurality of transistors being associated to a first circuit attribute;
• a control circuit on the chip and coupled to the first plurality of transistors, the control circuit capable to produce a reference resistance code corresponding to a substantial match of the resistance of the single external resistor based on a number of activated transistors in the first plurality of transistors;
• and
• at least a second plurality of transistors on the chip and coupled to the control circuit, the control circuit capable to activate or deactivate at least one transistor in the second plurality of transistors based on a shift of the reference resistance code to generate a resistance associated with a second circuit attribute different from the first circuit attribute associated with the first plurality of transistors.

A method, comprising:

• activating at least one of a first plurality of impedance-generation devices associated to a first circuit attribute, until an impedance of the activated impedance-generation devices substantially matches an impedance of a single external impedance element;
• based on a number of the activated impedance-generation devices, generating a reference impedance code corresponding to the impedance of the activated impedance-generation devices;
• shifting the reference impedance code;
• and
• using the shifted reference impedance code to activate at least one of a second plurality of impedance-generation devices to generate an impedance associated with a second circuit attribute different from the first circuit attribute associated with the first plurality of impedance-generation devices.

An article of manufacture, comprising:

• a machine-readable medium having stored thereon instructions to:
• activate at least one of a first plurality of impedance-generation devices associated to a first circuit attribute, until an impedance of the activated impedance-generation devices substantially matches an impedance of a single external impedance element;
• based on a number of the activated impedance-generation devices, generate a reference impedance code corresponding to the impedance of the activated impedance-generation devices;
• shift the reference impedance code;
• and
• use the shifted reference impedance code to activate at least one of a second plurality of impedance-generation devices to generate an impedance associated with a second circuit attribute different from the first circuit attribute associated with the first plurality of transistors.