Impedance calibration circuit, semiconductor memory device...

Details Impedance calibration circuit, semiconductor memory device... Impedance calibration circuit, semiconductor memory device...

2011-05-31

2011-05-31

Cho, James H. (Department: 2819)

Electronic digital logic circuitry

Signal sensitivity or transmission integrity

Bus or line termination

Reexamination Certificate

active

07952382

ABSTRACT:
An impedance calibration circuit for impedance matching between a semiconductor memory device and an external device includes a driving circuit and a comparing circuit. The driving circuit has a plurality of internal resistances, with one or more of the internal resistances being a variable resistance. The driving circuit compares the impedance of the internal resistances to the input/output impedance of the external device in order to provide a calibration voltage. The comparing circuit compares the calibration voltage to a reference voltage and provides a code signal for calibrating the impedance corresponding to output data with the input/output impedance of the external device. The impedance calibration circuit calibrates an impedance mismatch between the impedance calibration circuit and a data input/output driver by adjusting the impedance of the impedance calibration circuit through the variable resistance.

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