Gangadhar Burra

An RC Oscillator With Comparator Offset Cancellation

A fully-integrated 18.5 kHz RC time-constant-based oscillator is designed in 65 nm CMOS for sleep-mode timers in wireless sensors. A comparator offset cancellation scheme achieves 4× to 25× temperature stability improvement, leading to an accuracy of ±0.18% to ±0.55% over -40 to 90 °C. Sub-threshold operation and low-swing oscillations result in ultra-low power consumption of 130 nW. The architecture also provides timing noise suppression, leading to 10× reduction in long-term Allan deviation. It is measured to have a stability of 20 ppm or better for measurement intervals over 0.5 s. The oscillator also has a fast startup-time, with the period settling in 4 cycles.

F5: Low-power radios for sensor networks

Sensor node systems are expected to be a major growth field for semiconductor markets, and will connect to the cloud in a future cyber physical world. Wireless sensor networks (WSN) face multiple challenges from system design to low-power electronics and energy sources. Ultra-low-power radios are key elements in such systems, putting high demand on energy efficiency in different modes of operation (active, wake-up and sleep). This forum presents system perspectives and practical design aspects in various energy-efficient and short-range radio circuits and systems, including an introduction to various applications and their requirements for RF and digital signal processing in WSN systems. The technologies range from RF to digital signal processing and algorithms to give comprehensive understanding of recent advances. The forum begins with two high-level design talks on low power radio SoCs. The following four talks present ultra-low-power transceivers for body-area networks, sensor nodes, and health-monitoring applications. The last two talks cover efficient power management and emerging compression methodologies.

Commercially Viable Ultra-Low Power Wireless

This chapter looks at various practical aspects of architecting and designing low power wireless radios and systems-on-chip for applications such as consumer wearables, industrial automation etc. The chapter starts with a discussion on the need for industry accepted protocols for low power wireless and aspects in these protocols that lend themselves to low power implementations. With these protocols in place, we then look at practical design techniques of the RF/analog components, followed by a look at the Physical layer and the MAC and conclude the section by looking at the overall SoC design techniques for proper energy management. The chapter concludes by looking at the upcoming IEEE 802.11ah standard and discuss how this is adapted in an advantageous manner for low power wireless applications.