Current controlled delay line elements´ improvement study

The chain of delay elements creating delay lines are the basic building blocks of delay locked loops (DLLs) applied in clock distribution network in many VLSI circuits and systems. In the paper Current Controlled delay line (CCDL) elements with Duty Cycle Correction (DCC) has been described and investigated. The architecture of these elements is based on Switched-Current Mirror Inverter (SCMI) and CMOS standard or Schmitt type inverters. The primary characteristics of the described CCDL element have been compared with characteristics of two most popular ones: current starved, and shunt capacitor delay elements. The simulation results with real foundry parameters models in 180 nm, 1.8 V CMOS technology from UMC are also included. Simulations have been done using BSIM3V3 device models for Spectre from Cadence Design Systems.