Delay Locked Loop and clock delay method controlling delay time using shifter and adder

摘要

A delay locked loop that controls a delay time period by using a shifter and an adder includes a master delay locked loop and a slave delay locked loop. The master delay locked loop outputs a first digital value corresponding to one clock cycle of a first input clock signal. The slave delay locked loop receives the first digital value and delays a second input clock signal for a time period smaller than the one clock cycle of the first input clock signal. The slave delay locked loop includes a shifter, an operator, and a variable delay circuit. The shifter shifts the first digital value to generate a second digital value. The operator adds or subtracts an offset value to or from the second digital value to generate a third digital value, wherein the offset value varies according to a process, a voltage, and a temperature (PVT). The variable delay circuit delays the second input clock signal for a time period corresponding to the third digital value.