Resistor calibration

A method of calibrating a configurable resistor comprising:

• generating a reference voltage from an electrical current applied to a reference resistor having a target resistance;
• converting the reference voltage to a digital reference value;
• generating a first voltage from the electrical current applied to the configurable resistor while the configurable resistor is in a first configuration generated by a first configuration code;
• converting the first voltage to a first digital value;
• generating a second voltage from the electrical current applied to the configurable resistor while the configurable resistor is in a second configuration generated by a second configuration code to generate a second voltage;
• converting the second voltage to a second digital value;
• calculating from the digital reference value, the first digital value, and the second digital value, a target configuration code corresponding to the target resistance;
• and
• configuring the configurable resistor by providing the target configuration code to the configurable resistor.

A resistance calibration circuit, comprising:

• a configurable resistor configurable by a digital configuration code to have a configuration from a set of configurations corresponding to a set of stepped resistance values;
• a reference resistor of a predetermined resistance;
• a current mirror coupled to provide a mirrored current to a first terminal of the configurable resistor and to a first terminal of the reference resistor, a second terminal of the configurable resistor and a second terminal of the reference resistor connected to ground;
• an Analog-to-Digital Converter (ADC) coupled to the configurable resistor and the reference resistor, the ADC configured to convert a first voltage from the first terminal of the configurable resistor in a first configuration to a first digital value, convert a second voltage from the first terminal of the configurable resistor in a second configuration to a second digital value, and convert a voltage at the first terminal of the reference resistor to a digital reference value;
• a calculation circuit configured to calculate a difference between the first digital value and the second digital value divided by a number of configurations from the first configuration to the second configuration to obtain a step voltage, divide the difference between at least one of the first or second digital values and the digital reference value by the step voltage to obtain an offset, and generate a target code by applying the offset to the first or second digital value;
• and
• a sequencer to configure the configurable resistor according to the target code to have a resistance corresponding to the predetermined resistance.