Arnold: An eFPGA-Augmented RISC-V SoC for Flexible and Low-Power IoT End Nodes

A wide range of Internet of Things (IoT) applications require powerful, energy-efficient, and flexible end nodes to acquire data from multiple sources, process and distill the sensed data through near-sensor data analytics algorithms, and transmit it wirelessly. This work presents Arnold: a 0.5-to0.8-V, 46.83-mu W/MHz, 600-MOPS fully programmable RISC-V microcontroller unit (MCU) fabricated in 22-nm Globalfoundries GF22FDX (GF22FDX) technology, coupled with a state-of-theart (SoA) microcontroller to an embedded field-programmable gate array (eFPGA). We demonstrate the flexibility of the system-on-chip (SoC) to tackle the challenges of many emerging IoT applications, such as interfacing sensors and accelerators with nonstandard interfaces, performing on-the-fly preprocessing tasks on data streamed from peripherals, and accelerating near-sensor analytics, encryption, and machine learning tasks. A unique feature of the proposed SoC is the exploitation of body-biasing to reduce leakage power of the eFPGA fabric by up to 18x at 0.5 V, achieving SoA state bitstream-retentive sleep power for the eFPGA fabric, as low as 20.5 mu W. The proposed SoC provides 3.4x better performance and 2.9x better energy efficiency than other fabricated heterogeneous reconfigurable SoCs of the same class.

Automated summary

This study introduces Arnold: a low-power, high-performance programmable microcontroller unit that can handle and transmit various data needed for IoT applications.