Abstract: An impedance adjusting circuit for adjusting an impedance of an output buffer of a DDR2 memory, using an OCD impedance adjusting function, from a side of a memory controller, includes first and second terminals, first and second switches, a comparator, and a control circuit. The DDR2 memory has an OCD impedance adjusting function and includes a first output buffer and a second buffer each having a pull-up buffer and a pull-down buffer that receive an input signal in common and with impedances thereof capable of being variably set. The first and second terminals receive first and second signals output from the first buffer and the second buffers, respectively. The first and second switches are connected between the first terminal and the second terminal in series. The comparator compares a reference voltage VREF with a voltage at a connection node between the first and second switches.

Abstract: An impedance adjusting circuit for adjusting an impedance of an output buffer of a DDR2 memory, using an OCD impedance adjusting function, from a side of a memory controller, includes first and second terminals, first and second switches, a comparator, and a control circuit. The DDR2 memory has an OCD impedance adjusting function and includes a first output buffer and a second buffer each having a pull-up buffer and a pull-down buffer that receive an input signal in common and with impedances thereof capable of being variably set. The first and second terminals receive first and second signals output from the first buffer and the second buffers, respectively. The first and second switches are connected between the first terminal and the second terminal in series. The comparator compares a reference voltage VREF with a voltage at a connection node between the first and second switches.