Ultra-low power microcontrollers enabling energy harvesting applications: Page 6 of 7

June 19, 2019 //By Graeme Clark, Renesas Electronics
Ultra-low power microcontrollers enabling energy harvesting applications
In the aftermath of the Fukushima nuclear disaster in Japan, the Japanese government set up the LEAP (Low power Electronics Association and Project) initiative. This has the express aim of developing new, ultra-low power technologies to reduce energy consumption in a wide range of applications across the consumer and industrial market in Japan.

For the first time, the first SOTB embedded controller will allow powerful, connected applications to source energy from the environment. For this reason, it includes an integrated energy harvesting controller on chip.

This unique peripheral is designed to allow the microcontroller to start from an energy harvesting source and also to manage external rechargeable batteries or super capacitors to provide a power reservoir.

There are many issues that must be resolved when designing an energy harvesting application. For example, one of the biggest problems when using a normal microcontroller is managing the start-up current, as an energy source can normally only supply a small amount of current at any time. Yet a normal microcontroller will typically use significantly more current than is available from the energy source during the start-up phase.

The energy harvesting controller on the R7F0E017 manages this start up current along with the whole start up sequence, so thmicrocontroller starts up reliably and safely.

Figure 5 shows the energy harvesting controller implemented on the R7F0E017.

Figure 5: energy harvesting controller operation

The R7F0E017 is able to run safely from a pure energy harvesting power source due to the operation of the Energy Harvesting Controller.  The device can operate from a wide range of potential energy sources including solar power, vibration, pressure and temperature difference, and many others. The integrated energy harvesting controller, supported by very few inexpensive external components, completely manages the cyclic wake-up sequence of the microcontroller, only using the extremely low energy harvesting source current.  The energy harvesting controller includes internal ‘inrush-current’ protection and can operate at very low voltage level to avoid malfunctions during the start-up phase.

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