Delay control circuit and a memory module including the same

Abstract

A delay control circuit includes: a delay cell including a plurality of bias inverters, first RC circuits, and second RC circuits, the delay cell activates a number of first RC circuits in response to a step code, delays a signal by a delay time based on the number of the activated first RC circuits, and outputs the delayed signal; a ZQ calibrator including pull-up and pull-down circuits, the ZQ calibrator adjusts a number of activated pull-up and pull-down circuits, and inputs a pull-up and pull-down voltage, based on a calibration code to the bias inverters; and a step adjuster including a first ring oscillator including test delay cells, the step adjuster determining characteristics of the first and second RC circuits and activates a number of second RC circuits based on the characteristics and an operating frequency of the delay control circuit.