Patent ID: 7852112

Claim:
A termination circuit fabricated on a semiconductor die along with an electronic device having an externally accessible terminal, the termination circuit comprising: a programmable on-die termination (“ODT”) circuit coupled to the externally accessible terminal, the programmable ODT circuit providing the externally accessible terminal with an impedance using the combination of a terminating resistor and a controllable impedance element having an impedance that is controlled by at least one programming signal received by the programmable ODT circuit; and a programming circuit operable to provide the at least one programming signal to the ODT circuit so that the impedance provided by the combination of the terminating resistor and the controllable impedance element is substantially equal to a target impedance, the programming circuit comprising: a first resistor having a resistance that varies in a manner that substantially matches the manner in which a resistance of the terminating resistor varies; and a measurement circuit for measuring the impedance of the first resistor, the measurement circuit comprising: a second resistor coupled in series with the first resistor between first and second voltages to form a voltage divider having an output node between the first resistor and the second resistor; an analog-to-digital converter having an input coupled to the output node, the analog-to-digital converter generating a binary output signal indicative of a voltage at the output node of the voltage divider; and a register generating a plurality of the programming signals based on the binary output signal.