Patent ID: 8476923

Claim:
An impedance control circuit, comprising: a first impedance unit having an impedance value based on a first impedance code and configured to drive a first node with a first voltage; a first code generation unit configured to generate the first impedance code so that an impedance value of the first impedance unit and an impedance value of a external resistor are at a ratio of X:Y, wherein X and Y are different numbers; a plurality of dummy impedance units that receive the first impedance code and drive a second node with the first voltage, wherein the number of the dummy impedance units is Y/X; a second impedance unit having an impedance value based on a second impedance code and configured to drive the second node with a second voltage; and a second code generation unit configured to generate the second impedance code so that an overall impedance value of the dummy impedance units and an impedance value of the second impedance unit are at a ratio of X:Y.