HOW DOES IT WORK?

Solar Energy 2 Click is based on the EM8500, a power management controller with an energy harvesting interface from EM Microelectronic. The EM8500 is flexible in operation and can use different energy banks such as primary cell batteries, gold capacitors, and supercapacitors. It can work in harvesting sources in μW to mW range thanks to an ultra-low power DC-DC boost converter with very high efficiency. The EN8500 uses short-term storage (STS) element (100μF capacitor) to speed up system start-up. Besides fast start-up time over battery power, the LTS element (long-term storage) controls the minimum and maximum voltages, thus preventing damage to the battery. The onboard PMU with a built-in mechanism will extend the battery life if using a non-rechargeable battery.

The Solar Energy 2 Click can supply the external application through the VSUP and VAUX0-2 pins and correspondent GNDs of the 12-pin AUX COM header. On the VSUP pin, which is the main supply output, the wake-up function allows the automatic enabling of the supply after a given time. The AUX (auxiliary) output pins can output regulated voltages from 1.2 to 2.6V. Onboard EEPROM stores device configuration data, such as minimum and maximum voltage monitors, which will stop the DC-DC convertor, thus limiting the power loss. On EEPROM can be stored data for the VAUX0-2 and VGND0-2 pins, which besides the voltage output, can be used to store data for disconnecting any of these pins.

There are three modes in which Solar Energy 2 Click can operate. In Normal mode, the battery is connected and is in operating range. The LTS Protection mode is activated when the LTS voltage drops below minimum battery operation. In this mode is activated under-voltage protection. Finally, there is a Sleep mode where the VSUP is not supplied, and the communication with the host MCU is off. Sleep mode exit can be activated over the wake-up pin or by an internal timer.

The EN8500 also comes with several features, such as under-voltage, over-voltage, min/max voltage warning, USB connected status, lux-meter, and more. The lux-meter can run in three modes: Fully Automatic mode, Automatic Range Selection, and Fully Manual mode. The lux-meter determines current ranges by the harvesting element in 1 μA steps. On Solar Energy 2 Click, a VIN SEL switch allows the EN8500 to use the 5V rail from the mikroBUS™ socket or the 5V from the onboard USB Type-C connector as its supply. The EM8500 can detect the power on this line but can't determine if it is from the USB C or the 5V rail of the mikroBUS™ socket.

Although the EN8500 uses 5V rail only for its power management, the Solar Energy 2 Click can work with 3.3V systems, too. This Click board™ features the PCA9306, a dual bidirectional voltage level translator from Texas Instruments. As a low-voltage-side reference voltage, this translator uses the VSUP from the EN8500, while the high-side is the one selected via the VCC SEL jumper. In the same manner, several MOSFETs are used for other onboard interconnections.

Solar Energy 2 Click uses a standard 2-Wire I2C interface to communicate with the host MCU and supports Standard, Fast, and High-Speed communication. As mentioned, the EN8500 can exit sleep mode via the wake-up functions, which can be the WUP pin of the mikroBUS™ socket or the WUP pin of the AUX COM header. The EN8500 uses two more pins to send statuses to the host MCU. The HLV is used as a harvester-energy levels detection status, while the BLV is used for battery voltage levels monitoring.

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

SPECIFICATIONS