Digitally controlled voltage regulator using oscillator-based ADC with fast-transient-response and wide dropout range in 14nm CMOS

In this paper, we propose a digitally controlled voltage regulator with fast-transient-response using an oscillator based ADC implemented in 14nm CMOS technology. The transient response is critical to mitigate droop for large di/dt seen in cores and wide dropout range helps enable DVFS to improve power/performance ratio. In this work, we target 1-1.15V input voltage with output voltage range of 0.5-1.12V with minimum 30mV dropout, and load current range of >22x with 0.1A-2.2A at 50mV dropout with <;0.006mV/mA load regulation using 10-bit power-stage binary control and characterized using a slew-rate programmable synthetic resistive load on-die to mimic core with 18nF load capacitance implemented on-die using area over load.

I. Introduction;

Modern day multi-core CPU's want to enable per-core Dynamic Voltage Frequency Scaling (DVFS) for energy efficiency [1]. However, modern hand-held devices look for cost-optimization by merging of the supply rails on the System-on-Chip (SoC). A CPU core powered by a shared rail would have energy wastage if other blocks require higher voltage for high performance. To improve energy efficiency, a fully-integrated digitally-controlled voltage regulator (VR) with autonomous DVFS provides a cost-effective solution as digital circuits can operate better at sub-1V supply voltage and are easy to migrate across technologies [2]–[5].