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

The present invention relates to an impedance adjusting device that can increase the accuracy of calibration and termination operations without increasing the number of impedance code bits. The device includes a comparison unit, a counting unit, a reference impedance unit, a storage unit, and a termination unit. The comparison unit compares a reference voltage with a voltage of a calibration node and generates an impedance code based on the comparison. The reference impedance unit has an impedance value determined by the impedance code and is connected to the calibration node. The counting unit generates the impedance code and stores it in the storage unit. The termination unit includes a plurality of parallel resistors that are turned on / off based on the impedance code and a resistor that is turned on / off based on the value stored in the storage unit. The device can be used to adjust the impedance of an interface node connected to a data pad or other external devices.

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.

Images