An Energy Ef ficient Generator With Fast Ramp-Up Time for Mobile DRAM Kyu-Y oung Kim, Y onghwan Kim, Doo-Chan Lee, Y u-Ri Kang, Hoonki Kim

Abstract

An energy efficient generator with fast ramp-up time for mobile DRAM is presented in this paper. Instead of using a fixed pumping clock frequency as in the conventional gener- ator, the proposed generator adopts a voltage-controlled oscil- lator (VCO) and uses variable pumping frequencies to improve the ramp-up time as well as energy ef ficiency. Numerical results show that the VCO based generators achieve energy savings of up to 34% with 40% improvement on ramp-up time when compared to the conventional ring oscillator (RO) based design. Our pro- posed generator, which uses a three-stage voltage doubler as a charge pump, was implemente d and fabricated in CMOS 0.13 m process. The generator chip’s core occupies 0.6 mm area and consumes 1162 nJ (average power of 47.8 mW during 24 s ramp-up time) while generating 3.0 V output voltage with 1.0 nF load capacitor, 2.0 mA current load and 1.2 V supply voltage.