Analog Integrated Circuits and Signal Processing

, Volume 98, Issue 2, pp 321–329 | Cite as

A CMOS PFM buck converter employing a digitally programmable voltage level-shifting technique

  • Jong Gu Kim
  • Jin-Woo So
  • Kwang Sub YoonEmail author


This paper describes a CMOS pulse frequency modulation (PFM) buck converter employing a digitally programmable voltage level-shifting technique capable of adjusting peak inductor current and output ripple voltage for different load currents. The conventional PFM buck converters employ either an adaptive delay time control circuit or a fixed delay time control circuit to control output ripple voltage and power efficiency with the switching frequency. However, they suffer from a large peak inductor current, resulting in reduced power efficiency. The digitally programmable voltage level-shifting circuit, based on a common source amplifier, is capable of sensing inductor current through the voltage drop caused by on-resistance of the power switch, and can control peak inductor current. The precision needed to control the magnitude of the peak inductor current can be obtained with the number of bits in the digitally programmable voltage level-shifting circuit that are dependent on the input common mode range of the comparator. Employment of one comparator with pre-control logic and post-control logic circuits allows the proposed circuit to improve power efficiency by removing additional circuits, compared with the conventional PFM buck converters. The proposed converter was implemented with a 180 nm CMOS process. The effective chip size of the core block occupies 900μm × 590μm. The proposed PFM mode buck converter with a precision of four bits to control peak inductor current is capable of accommodating an input voltage range of 2.7–3.3 V, and can produce output voltage of 1.2 V. The operational switching frequency measured is on the order of several to several hundred kHz, the load current range is under 150 mA, and the measured output ripple voltage varied, depending on the digital programming status. The measured power efficiency ranged between 70 and 84%.


PFM buck converter Digitally programmable Voltage level-shifting Peak inductor current CMOS 



This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2010-0020163). The chip was fabricated under the IDEC MPW program.


  1. 1.
    Hiremath, S.,Yang, G., & Mankodiya, K. (2014). Wearable internet of things: Concept architectural components and promises for person-centered healthcare. In Wireless Mobile Communication and Healthcare (Mobihealth) 2014 EAI 4th International Conference on, pp. 304–307.Google Scholar
  2. 2.
    Ko, U. (2016). Ultra-low power SoC for wearable & IoT. In VLSI Technology, Systems and Application (VLSITSA), pp. 1–1.Google Scholar
  3. 3.
    Yoon, SW., Petrov, B., & Liu, K. (2015). Advanced wafer level technology: Enabling innovations in mobile. In IoT and wearable electronics, Electronics Packaging and Technology Conference (EPTC).Google Scholar
  4. 4.
    Sahu, B., & Rincon-Mora, G. A. (2007). An accurate, low-voltage, CMOS switching power supply with adaptive on-time pulse-frequency modulation(PFM) control. IEEE Transactions on Circuits and Systems I: Regular Papers, 54(2), 312–321.CrossRefGoogle Scholar
  5. 5.
    Tao, C., & Fayed, A. A. (2012). A low-noise PFM-controlled buck converter for low-power applications. IEEE Transactions on Circuits and Systems I, 59(12), 3071–3080.MathSciNetCrossRefGoogle Scholar
  6. 6.
    Chen, C.-L., Hsieh, W.-L., Lai, W.-J., Chen, K.-H., & Wang, C.-S. (2008). A new PWM/PFM control technique for improving efficiency over wide load range. In Proceedings of IEEE International Conference Electron, Circuits, Systems, pp. 962–965.Google Scholar
  7. 7.
    Ma, F., Chen, W., & Wu, J. (2007). A monolithic current-mode buck converter with advanced control and protection circuits. IEEE Transactions on Power Electronics, 22(5), 1836–1846.CrossRefGoogle Scholar
  8. 8.
    Yuan, B., Lai, X.-Q., Wang, H.-Y., & Shi, L.-F. (2013). High-efficient hybrid buck converter with switch-on-demand modulation and switch size control for wide-load low-ripple applications. IEEE Transactions on Microwave Theory and Techniques, 61(9), 3329–3338.CrossRefGoogle Scholar
  9. 9.
    Tsai, C.-H., Chen, B.-M., & Li, H.-L. (2016). Switching frequency stabilization techniques for adaptive on-time controlled buck converter with adaptive voltage positioning mechanism. IEEE Transactions on Power Electronics, 31(1), 443–451.CrossRefGoogle Scholar
  10. 10.
    Fu, W., Tan, S. T., Radhkrishnan, M., Byrd, R., & Fayed, A. A. (2016). A DCM only buck regulator with hysteretic-assisted adaptive minimum-on-time control for low-power microcontrollers. IEEE Transactions on Power Electronics, 31(1), 418–429.CrossRefGoogle Scholar
  11. 11.
    Kim, S. J., Choi, W. S., Pilawa-Podgurski, R., & Hanumolu, P. K. (2018). A 10 MHz 2-800 mA 0.5-1.5 V 90% peak efficiency time-based buck converter with seamless transition between PWM/PFM modes. IEEE Journal of Solid-State Circuits, 53(3), 814–824.CrossRefGoogle Scholar
  12. 12.
    Park, Y. J., Park, J. H., Kim, H. J., Ryu, H. C., Kim, S. Y., Pu, Y. G., et al. (2017). A design of a 92.4% efficiency triple mode control DC–DC buck converter with low power retention mode and adaptive zero current detector for IoT/Wearable applications. IEEE Transactions on Power Electronics, 32(9), 6946–6960.CrossRefGoogle Scholar

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© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Electronic EngineeringINHA UniversityIncheonKorea

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