Biblio

This paper presents a scalable single-input-multiple-output DC/DC converter targeting load transient response and security improvement for low-power System-on-Chips (SoCs). A two-stage modular architecture is introduced to enable scalability. The shared switched-capacitor pre-charging circuits are implemented to improve load transient response and decouple correlations between inputs and outputs. The demo version of the converter has three identical outputs, each supporting 0.3V to 0.9V with a maximum load current of 150mA. Based on post-layout simulation results in 32nm CMOS process, the converter output provides 19.3V/μs reference tracking speed and 27mA/ns workload transitions with negligible voltage droops or spikes. No cross regulation is observed at any outputs with a worst-case voltage ripple of 68mV. Peak efficiency reaches 85.5% for each output. With variable delays added externally, the input-output correlations can change 10 times and for steady-state operation, such correlation factors are always kept below 0.05. The converter is also scaled to support 6 outputs with only 0.56mm2 more area and maintains same load transient response performance.

In this paper we propose a novel integrated DC/DC converter featuring a single-input-multiple-output architecture for emerging System-on-Chip applications to improve load transient response and power side-channel security. The converter is able to provide multiple outputs ranging from 0.3V to 0.92V using a global 1V input. By using modularized circuit blocks, the converter can be extended to provide higher power or more outputs with minimal design complexity. Performance metrics including power efficiency and load transient response can be well maintained as well. Implemented in 32nm technology, single output efficiency can reach to 88% for the post layout models. By enabling delay blocks and circuits sharing, the Pearson correlation coefficient of input and output can be reduced to 0.1 under rekeying test. The reference voltage tracking speed is up to 31.95 V/μs and peak load step response is 53 mA/ns. Without capacitors, the converter consumes 2.85 mm2 for high power version and only 1.4 mm2 for the low power case.

This paper presents a sequence switching control (SSC) scheme for buck converters with a series-inductor auxiliary circuit, aiming at improving the load transient response. During an unloading transient, the series inductor is controlled as a small equivalent inductance so as to achieve a fast transient regulation. While in the steady state, the series inductor behaves as a large inductance to reduce the output current ripple. Furthermore, on the basis of the proposed variable inductance circuit, a SSC control scheme is proposed and implemented in a digital form. With the proposed control scheme the unloading transient event is divided into n+1 sub-periods, and in each sub-period, the capacitor-charge balance principle is used to determine the switching time sequence. Furthermore, its feasibility is validated in experiment with a 12V-3.3V low-voltage high-current synchronous buck converter. Experimental results demonstrate that the voltage overshoot of the proposed SSC scheme has improved more than 74% compared to that of the time-optimal control (TOC) scheme.