| 摘要 |
PURPOSE: A semiconductor device having an impedance control function, which is capable of matching impedance with an external device, is provided to eliminate a noise of high frequency wave caused by an external resistance by utilizing a low-pass filter of a comparator. CONSTITUTION: A resistor (RZQ) corresponding to a system impedance is combined with a ZQ pad (100). A code detection section (110) detects a fed-back count code (CTQx), generates a pre-set first voltage (Vref), and outputs a current signal, which is variable in accordance with the detected count code (CTQx), to the ZQ pad (100). A filtering section (120) filters and outputs noise components contained in a pre-set first voltage (Vref) and a second voltage (VZQ) applied to the ZQ pad (100), respectively. A comparator (140) compares level values of the first and the second voltages (Vref, VZQ) filtered by the filtering section (120), and outputs a count enable signal (U/D) when the level values of the first and the second voltages (Vref, VZQ) are discord with each other. A code generation section (160) generates the count code (CTQx) by counting upwardly or downwardly from the initial value in response to a count enable signal (U/D) from the comparator (140), and feeds back the count code (CTQx) to the code detection section (110). A data driving section (180) latches the count code (CTQx) generated from the code generation section (160) in response to an elevating edge of an output enable signal (OE), and buffers and outputs the data inputted through data lines (DL, DLB) by the latched count code (CTQx) in response to a descending edge of the output enable signal (OE).
|
