Decoder and pass transistor based digitally controlled linear delay element

With advancement and scaling in Integrated circuit design, the accuracy of clock circuitry plays an increasingly important role. Timing precision is important to reduce the synchronization problem in digital circuits. The precise timing of pulse is also extremely important for designing asynchronous circuits. Delay element is the basic building block for asynchronous circuits. Many circuits of digitally controlled delay elements have been reported in literature. The reported circuits provide a delay which is a non linear function of digital inputs. Non linearity of delay in reported circuits affects the accuracy of time because of which they cannot be used in real world applications. This paper presents a novel circuit of decoder and pass transistor based delay element. The proposed circuit is designed for 3 bits and it provides a delay which is a linear function of digital inputs. The design is implemented in cadence using 180 nm CMOS technology.