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A practical method for coupled oscillator design is elaborated. The topology analysis of a coupled oscillator, the ways of simulating its sensitivity, initializing its operation, and the oscillation frequency enhancement with nMOS phase couplers are presented. We have developed a write strategy system for DVD with a coupled oscillator using these techniques. In addition, we have also developed a low-power-oriented multiphase generator for mobile phones with our newly devised multiphase level shift system (M-LS). The M-LS has established superiority in its low power consumption because of no short current. Moreover, we have applied the method of output phase-accuracy improvement using a resistor ring to the M-LS. Two test chips are fabricated and the design method is validated. The first coupled oscillator has a resolution of 32 ps and a phase accuracy of -1.0 to 0.8 LSB at 490 MHz, corresponding to 16times DVD write speed. The second one consumes 1 mA and has a high phase accuracy of 0.5 LSB at 123 MHz.
Date of Publication: April 2008