A Variable Output Voltage Switched-Capacitor DC-DC Converter with Pulse Density and Width Modulation (PDWM) for 57% Ripple Reduction at Low Output Voltage

Xin ZHANG  Yu PU  Koichi ISHIDA  Yoshikatsu RYU  Yasuyuki OKUMA  Po-Hung CHEN  Takayasu SAKURAI  Makoto TAKAMIYA  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.6   pp.953-959
Publication Date: 2011/06/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.953
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuits and Related SoC Integration Technologies)
DC-DC converter,  low ripple,  low voltage,  pulse density modulation,  pulse width modulation,  switched-capacitor,  

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In this paper, a novel switched-capacitor DC-DC converter with pulse density and width modulation (PDWM) is proposed with reduced output ripple at variable output voltages. While performing pulse density modulation (PDM), the proposed PDWM modulates the pulse width at the same time to reduce the output ripple with high power efficiency. The prototype chip was implemented using 65 nm CMOS process. The switched-capacitor DC-DC converter has 0.2-V to 0.47-V output voltage and delivers 0.25-mA to 10-mA output current from a 1-V input supply with a peak efficiency of 87%. Compared with the conventional PDM scheme, the proposed switched-capacitor DC-DC converter with PDWM reduces the output ripple by 57% in the low output voltage region with the efficiency penalty of 2%.