eFuse 3 Click, as its foundation, uses the NIS6150, a self-protected, resettable electronic fuse from ON Semiconductor that contains circuits to monitor the input voltage, output voltage, output current, and die temperature. It comes with ENABLE feature with a separate 'flag' for fault identification, adjustable output current-limit protection with a thermal shutdown, and a current monitoring pin. The NIS6150 also includes an internal temperature sensing circuit that senses the temperature on the die of the power FET. If the temperature reaches 175°C, the device will shut down and remove power from the load.

This Click board™ communicates with MCU through the 3-Wire SPI serial interface using the MCP3551, a 22bit sigma-delta ADC from Microchip. The MCP3551 is used for current monitoring purposes by converting the output current from NIS6150 IMON pin with a very high resolution of 22 bits and low noise to digital data, which can be obtained via the SPI interface of the Click board™. This ADC uses the reference voltage, the 4.096V reference voltage level provided by the MCP1541 from Microchip powered from the +5V mikroBUS™ power rail, resulting in high accuracy and stability. A resistor that connects to the middle connector on this Click board™, labeled as Rlim, sets the overload and short circuit current limit levels.

The VSL pin routed to the RST pin on the mikroBUS™ socket allows the overvoltage clamp to be set at either a 5.7 V or 6.5 V minimum by pulling this pin to a low logic state. It monitors the output voltage, and if the input exceeds the output voltage, the gate drive of the main FET is reduced to limit the output. This is intended to allow operation through transients while protecting the load. If an overvoltage condition exists for many seconds, the device may overheat due to the voltage drop across the FET combined with the load current. In this event, the thermal protection circuit would shut down the device.

The eFuse 3 Click also has active two additional pins of the mikroBUS™ socket, the INT and PWM pins labeled as FLG and EN. The Enable feature, routed to the PWM pin on the mikroBUS™ socket, provides a digital interface to control the output of the eFuse. That's why when this pin is pulled to a low logic state - the eFuse is turned OFF. On the other hand, the 'flag' pin routed to the INT pin on the mikroBUS™ socket sends information to the MCU regarding the state of the chip. If a thermal fault occurs, the voltage on this pin will go to a low state to signal a monitoring circuit that the device is in thermal shutdown.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to properly use the SPI communication lines. 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.