A 65-nm, 1-A Buck Converter With Multi-Function SAR-ADC-Based CCM/PSK Digital Control Loop

This paper proposes a 1-A, 6.4-MHz switching frequency DC-DC converter with embedded digital controller, implemented in 65-nm CMOS technology. The proposed DC-DC converter, exploiting a customized, multi-function SAR ADC and a non-linear PID controller, can switch automatically between continuous-conduction mode and pulse-skipping mode, thus maintaining a fairly large efficiency also for light loads. Moreover, a feedforward path in the digital control loop, implemented using the SAR ADC for converting also the battery voltage, significantly improves the line transient performance. The DC-DC converter, which occupies an area of 0.038 mm2 , consumes 115.5 μA, and requires an external inductance as low as 470 nH, is particularly suited for portable applications.

[1]  Justin Gaither,et al.  A robust digital DC-DC converter with rail-to-rail output range in 40nm CMOS , 2010, 2010 IEEE International Solid-State Circuits Conference - (ISSCC).

[2]  Michael Fulde,et al.  A digitally controlled DC-DC converter for SoC in 28nm CMOS , 2011, 2011 IEEE International Solid-State Circuits Conference.

[3]  Ke-Horng Chen,et al.  Zero current detection technique for fast transient response in buck DC-DC converters , 2008, 2008 IEEE International Symposium on Circuits and Systems.

[4]  D. Maksimovic,et al.  Digital PWM/PFM controller with input voltage feed-forward for synchronous buck converters , 2008, 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition.

[5]  D. Maksimovic,et al.  Digital pulse width modulator architectures , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[6]  A. Prodic,et al.  Design of a digital PID regulator based on look-up tables for control of high-frequency DC-DC converters , 2002, 2002 IEEE Workshop on Computers in Power Electronics, 2002. Proceedings..

[7]  Dragan Maksimovic,et al.  Feed-forward pulse-width modulators for switching power converters , 1995 .

[8]  Tao Liu,et al.  A digitally controlled DC-DC buck converter with lossless load-current sensing and BIST functionality , 2011, 2011 IEEE International Solid-State Circuits Conference.

[9]  Bertan Bakkaloglu,et al.  A 300mA 14mV-ripple digitally controlled buck converter using frequency domain ΔΣ ADC and hybrid PWM generator , 2010, 2010 IEEE International Solid-State Circuits Conference - (ISSCC).

[10]  Jinwen Xiao,et al.  A 4/spl mu/A-quiescent-current dual-mode buck converter IC for cellular phone applications , 2004, 2004 IEEE International Solid-State Circuits Conference (IEEE Cat. No.04CH37519).

[11]  V. Yousefzadeh,et al.  Nonlinear digital PID controller for DC-DC converters , 2008, 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition.

[12]  Andrea Baschirotto,et al.  A 65-nm, 1-A buck converter with multi-function SAR-ADC-based CCM/PSK digital control loop , 2011, 2011 Proceedings of the ESSCIRC (ESSCIRC).

[13]  Seth R. Sanders,et al.  Converter IC for Cellular Phone Applications , 2004 .

[14]  A. Prodic,et al.  Programmable Analog-to-Digital Converter for Low-Power DC–DC SMPS , 2008, IEEE Transactions on Power Electronics.

[15]  Anantha Chandrakasan,et al.  20 $\mu$ A to 100 mA DC–DC Converter With 2.8-4.2 V Battery Supply for Portable Applications in 45 nm CMOS , 2011, IEEE Journal of Solid-State Circuits.