DELAY TIME CONTROLLING CIRCUIT AND METHOD FOR CONTROLLING DELAY TIME OF VARIABLE DELAY CIRCUIT WITH ADJUSTABLE DELAY TIME

摘要

PROBLEM TO BE SOLVED: To provide a delay time controlling circuit and method for controlling a delay time of a variable delay circuit whose delay time can be controlled. SOLUTION: The delay time controlling circuit comprises a controller for generating a delay control signal in m (m is an integer) bits to control a delay time of the variable delay circuit in response to a first control signal, a fuse unit for receiving the delay control signal, blowing a fuse provided inside in response to a fuse blowing signal when the delay control signal reaches an object delay time and generating an m-bit fuse code signal corresponding to a logical value of the blown fuse, a selector fuse for being blown in response to the fuse blowing signal, and a multiplexer that is controlled by the selector fuse to select the delay control signal or the fuse code signal and outputs the selected signal to a variable delay circuit. The controller is provided with a register and then a semiconductor memory device whose packaging is completed can control the delay time without the need for additional works.