SOTB-based embedded controller enables next step for energy harvesting

16th November 2018
Caroline Hayes


Batteries in IoT devices could be redundant as energy harvesting progresses with reduced active and standby current consumption in the RF70E embedded controller, based on Renesas Electronics’ silicon on thin buried oxide (SOTB) process technology.

According to the company the levels of current consumption has not been able to be realised before and are a move closer to the elimination of batteries in products using light or vibration for energy harvesting.

Without batteries, IoT devices can become maintenance-free sensing devices with endpoint intelligence in industrial, healthcare, enterprise, residential and infrastructure applications, as well as in drones and health and fitness consumer products.

The 32bit Arm Cortex-M0+-based controller operates at up to 64MHz to locally process sensor data and execute complex analysis and control functions. Active current is 20μA/MHz and deep standby current is just 150nA, or approximately 10% that of conventional low-power microcontrollers, says the company.

The configurable Energy Harvester Control (EHC) function enables direct connection to different types of ambient energy sources, such as solar, vibration, or piezoelectric, while protecting against harmful inrush current at start-up. It also manages the charging of external power storage devices such as supercapacitors or optional rechargeable batteries.

For low power system operation, the controller can sense and capture external analogue signals at all times because the 14bit ADC consumes only 3uA current. Another characteristic is that up to 256kbyte of SRAM data can be retain, consuming just 1nA per Kbyte. Low power hardware techniques are used to convert graphics data, including rotation, scroll, and colorisation, to drive an external display using memory in pixel (MIP) LCD technology that is claimed to consume virtually no power to retain an image.

For security there is a true random number generator ID for each device and AES encryption acceleration.

Samples are available now for beta customers, and scheduled to be available for general customers from July 2019. Mass production is scheduled to begin October 2019.


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