RESUMEN
Improving system lifetime and robustness is a key to advancing self-powered platforms for real world applications. A complete self-powered, battery-less, wearable platform requires a microwatt-power system-on-chip (SoC), operating reliably within this budget, capable of surviving long periods without charging, and recovering from power loss to its previous state. To meet these requirements, we designed a wireless sensing heterogeneous system-in-package (SiP) containing an ultra-low power (ULP) SoC, a non-volatile boot memory (NVM), and a 2.4 GHz frequency shift key (FSK) radio, all integrated with custom ULP interfaces. The SoC includes a fully integrated energy harvesting platform power manager (EH-PPM) to power the SiP and other commercial sensors. The EH-PPM is designed for small loads and powers the SoC and peripherals while drawing very low operating current. The SoC also includes a digital system data-flow for sensing applications, an analog front end for ECG signal acquisition, and a cold-boot management system (CBMS) for boot and recovery from the NVM. The CBMS enables integration of the SoC with the ULP NVM to create a wearable formfactor, self-powered system capable of recovery from power loss. The SoC also includes a radio interface tightly integrated with a compression accelerator to efficiently communicate with the FSK transmitter and reduce the FSK's transmission time. This tight integration between accelerators on the SoC and peripherals is another feature that reduces the system's power consumption by reducing the code size and number of memory accesses required to perform an operation. The SoC consumes 507 nW average power while running free-fall detection, 519 nW average power while measuring ambient temperature, and 1.02 µW during continuous ECG monitoring and post-processing.
Asunto(s)
Suministros de Energía Eléctrica , Dispositivos Electrónicos Vestibles , Conversión Analogo-Digital , Electrocardiografía , Procesamiento de Señales Asistido por Computador , Temperatura , Análisis de Ondículas , Tecnología InalámbricaRESUMEN
This paper presents a batteryless system-on-chip (SoC) that operates off energy harvested from indoor solar cells and/or thermoelectric generators (TEGs) on the body. Fabricated in a commercial 0.13 µW process, this SoC sensing platform consists of an integrated energy harvesting and power management unit (EH-PMU) with maximum power point tracking, multiple sensing modalities, programmable core and a low power microcontroller with several hardware accelerators to enable energy-efficient digital signal processing, ultra-low-power (ULP) asymmetric radios for wireless transmission, and a 100 nW wake-up radio. The EH-PMU achieves a peak end-to-end efficiency of 75% delivering power to a 100 µA load. In an example motion detection application, the SoC reads data from an accelerometer through SPI, processes it, and sends it over the radio. The SPI and digital processing consume only 2.27 µW, while the integrated radio consumes 4.18 µW when transmitting at 187.5 kbps for a total of 6.45 µW.