Patent ID: 7733120

Claim:
An impedance adjustment circuit for adjusting a resistance value of a resistor under adjustment, the circuit comprising: a comparator that compares a resistance value of a first resistor and a resistance value of a replica resistor that forms a replica of the resistor under adjustment; a replica resistor control counter that counts up or down based on a result of comparison by the comparator to produce a control signal that variably controls the resistance value of the replica resistor; a resistor-under-adjustment control signal holding circuit that holds a control signal that variably controls the resistance value of the resistor under adjustment; and a monitor circuit that receives a state of the replica resistor control counter and an output of the resistor-under-adjustment control signal holding circuit and that delivers an output of the resistor-under-adjustment control signal holding circuit to the resistor-under-adjustment control signal holding circuit, in case the difference between the state of the replica resistor control counter and the output of the resistor-under-adjustment control signal holding circuit is within a preset range.