Impedance adjusting device

Abstract

An impedance adjusting device includes: a calibration node; a comparison unit configured to compare a reference voltage with a voltage of the calibration node; a counting unit configured to generate an impedance code according to a comparison result of the comparison unit; a reference impedance unit having an impedance value according to the impedance code and connected to the calibration node; a storage unit configured to store the comparison result of the comparison unit upon the generation of the impedance code being completed; an interface node; and a termination unit configured to terminate the interface node, the termination unit including a plurality of parallel resistors configured to be turned on / off according to the impedance code, and a parallel resistor configured to be turned on / off according to a value stored in the storage unit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority of Korean Patent Application No. 10-2009-0117428, filed on Nov. 30, 2009, which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]An embodiment of the present invention relates to an impedance adjusting device for matching impedances of input / output pads for communication with external circuits in a semiconductor device.[0003]A variety of semiconductor devices are implemented with integrated circuit chips, such as CPUs, memories, and gate arrays. Such semiconductor devices are incorporated in various electronic products, such as personal computers, servers, and workstations. In most cases, semiconductor devices include receiving circuits to receive a variety of external signals through input pads, and output circuits to output a variety of internal signals through output pads.[0004]Meanwhile, as the operating speeds of the electronic products increase, amplitude sw...

AI Technical Summary

Benefits of technology

[0024]An embodiment of the present invention is directed to an impedance adjusting device which is capable of increasing the accuracy of the calibration and termination operations, without increasing the number of impedance code bits.

Problems solved by technology

However, as the amplitude swings of the signals are reduced, the influence of external noise is increased, and signal reflectivity due to impedance mismatching at interfaced terminals becomes more severe.

The impedance mismatching is caused by external noise or variations in power supply voltage, operating temperature or fabrication process.

When impedance mismatching occurs, high-speed data transmission may be difficult, and data outputted from data output terminals of the semiconductor device may be distorted.

Therefore, when the receiving circuit of the semiconductor device receives the distorted output signals through the input terminals, setup / hold failure or an incorrect determination of input levels may frequently occur.

However, if the number of bits of the impedance codes PCODE and NCODE is increased, then the complexity of the calibration circuit is also increased.

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