Patent ID: 8610458

Claim:
An impedance control circuit comprising: a comparison circuit configured to: compare a voltage level of an impedance node with a reference voltage, generate an up/down signal indicating whether the voltage at the impedance node is greater or less than the reference voltage, and generate an impedance control voltage that has a voltage level corresponding to a difference between the voltage at the impedance node and the reference voltage; a counter unit configured to increase or decrease a value of an impedance control code having N+1 bits based on the up/down signal; a first impedance unit configured to terminate an impedance node using an impedance value that is based on N bits of the impedance control code; and a second impedance unit configured to: terminate the impedance node using an impedance value based on a single bit, of the N+1 bits, of the impedance control code, if the voltage at the impedance node is less than or equal to the reference voltage or greater than or equal to the reference voltage plus a voltage equal to a change in the voltage at the impedance node produced by a bang-bang error, and terminate the impedance node using an impedance value based on the impedance control voltage, if the voltage at the impedance node is greater than the reference voltage and less than the reference voltage plus a voltage equal to a change in the voltage at the impedance node produced by a bang-bang error.