Programmable delay element using memristor and case study in delay lock loop

Abstract

Until now, only few researches have been reported in application of memristor in analog circuits, despite the actual fact that analog memristor switching (MRS) is more intriguing than digital memristor switching. In this research, potential application of memristor in analog circuit is explored. A programmable delay element (PDE) which consists of memristor resistance write circuit, read circuit and delay element is presented. Operation of proposed PDE started with write circuit to program memristor resistance and read circuit to read the current from memristor that change according to resistance. A sample/hold circuit acted as nonvolatile characteristic of actual memristor that hold memristor current when voltage supply is off. Memristor current then supplied to delay element to regulate the delays. If memristor resistance is small, current flow is large and resulting in small delay and otherwise. This is how memristor able to program the delay of PDE. Maximum and minimum memristor current achieved are 265μΑ and 197μΑ that results in delay range from 1.31ms to 1.68 ms for 167 MHz input clock. Next, a case study of proposed PDE application in delay locked loop circuit (DLL) is discussed to prove PDE functionality in more complex system. For input frequency 5MHz, both conventional DLL and DLL with proposed PDE successfully locked input and output clock. Operating frequency range of conventional DLL is 5–7(MHz), while for DLL with PDE is 3–5 (MHz). This shows comparable result of CMOS DLL and DLL with PDE.