Abstract: A variable impedance control circuit for a semiconductor device reduces susceptibility to power supply variations and improves impedance matching by utilizing the same power supply for portions of the array driver and for the transistor arrays used for impedance matching.

Abstract: A reference circuit, which is applied to a ferroelectric random access memory device, includes a polarization state detection circuit having dummy cells with ferroelectric capacitors. The detection circuit checks polarization states of the ferroelectric capacitor in the dummy cells using dumping voltages of different levels, and generates pass/fail signals as a check result. The generated pass/fail signals are decoded, using themselves as selection information for selecting one of reference voltages, of different levels, which are generated from a reference voltage generation circuit. Thus, it is possible to generate an optimal reference voltage, which senses a ferroelectric capacitor polarization state that is changed with time.

Abstract: A semiconductor memory device includes input/output circuitry capable of operating in sync with an externally provided I/O clock signal. A data in buffer and a data out buffer provide for serial to parallel conversion of write data and, conversely, parallel to serial conversion of read data. The data buffers can be synchronized with the external I/O clock signal thereby decoupling their operation from the internal system clock signal. This strategy improves I/O bandwidth and further provides for matching different numbers of bit lines or word sizes as between the I/O data port and the memory array itself. An internal I/O clock generator can be provided for generating I/O clock signals, again without the limitation of synchronizing to the internal system clock signal.