Vol: 56(70) No: 4 / December 2011 |
Delay Locked Loop Clock Generator in Low Power VLSI IC Design
Goran S. Jovanović
University of Niš, Faculty of Electronic Engineering, A. Medvedeva 14, 18000 Niš, Serbia, phone: +381 (18) 529-660, e-mail: goran. email@example.com
Darko B. Mitić
University of Niš, Faculty of Electronic Engineering , A. Medvedeva 14, 18000 Niš, Serbia, e-mail: firstname.lastname@example.org
Mile K. Stojčev
University of Niš, Faculty of Electronic Engineering, A. Medvedeva 14, 18000 Niš, Serbia, e-mail: email@example.com
Dragan S. Antić
University of Niš, Faculty of Electronic Engineering , A. Medvedeva 14, 18000 Niš, Serbia, e-mail: firstname.lastname@example.org
Keywords: low power design, frequency multiplier, PLL, DLL, jitter
In order to decrease the power consumption of embedded systems, the power management unit (PMU) is used. PMU is responsible for coordinating many functions, including: monitoring power connections and battery charges, controlling power to other integrated circuits, identifies idle or low active parts of VLSI IC and to apply lower frequency clock to supply their operations, shutting down unnecessary system components when they are left idle, controlling sleep and power functions (on and off), regulating the real-time clock, etc. Basic components of PMU are : threshold detector, timer and control logic. The control logic is responsible for generating control signals for clock/power switching on/off, adjusting voltage/clock frequency, etc. We consider herein one approach for synthesis of multi-frequency and multi-phase clock generator as constituent of PMU which is based on delay locked loop (DLL) control principle. Contrary to phase locked loop (PLL) control, the DLL offers a simple implementation and lower jitter in the clock signal. The clock generator is implemented in 1.2 m CMOS technology using dedicated delay oriented design methodology. It converts a square wave signals to in-phase, quadrature-phase and eight-phase square wave signals, and multiplies the frequency by two- and four-times. The output frequency of the multi-frequency and multi-phase clock generator extends from 20MHz to 80MHz.
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