Patent ID: 8143912

Claim:
An impedance adjustment circuit for adjusting terminal resistance, the impedance adjustment circuit comprising: a resistance evaluation unit comprising: a first resistor; a voltage-to-current conversion unit, coupled to a reference voltage and the first resistor, for converting the reference voltage to a reference current through the first resistor; a current calculation unit, coupled to the voltage-to-current conversion unit, for generating a comparative current according to the reference current and a control signal, wherein the comparative current is adjusted by the control signal; a second resistor, coupled to the current calculation unit, for converting the comparative current to a comparative voltage; a comparator, coupled to the second resistor and the reference voltage, for generating a comparing result according to the comparative voltage and the reference voltage; and a successive approximation register (SAR), coupled to the comparator and the current calculation unit, for performing a successive approximation operation according to the comparing result to set the control signal until a ratio of the comparative current to the reference current approximates a ratio of the first resistor to the second resistor; and a terminal resistor unit, coupled to the resistance evaluation unit, comprising a plurality of unit resistors, the terminal resistor unit determining the number of parallel-connected resistors of the plurality of unit resistors according to the control signal to provide a matched terminal resistance.