Current 4 Click as its foundation uses the INA250, a current-sense amplifier with a high-precision, low-drift shunt resistor which can deliver highly accurate measurements over a wide temperature range from Texas Instruments. The INA250 measures the voltage developed across the internal current-sensing resistor when current passes through it. The integrated 2mΩ shunt resistor offers 0.1% tolerance and low drift of 15pmm/°C, enabling the higher performance of the end equipment. This amplifier allows for high-accuracy current measurements at common-mode voltages and offers a maximum error of 0.84% over the temperature range from -40 to +125°C.

Current 4 Click communicates with MCU using only one pin routed on the AN pin of the mikroBUS™ socket. The output analog signal from INA250 is forwarded to the input of the operational amplifier, the LMV321 low-voltage rail-to-rail OpAmp from Texas Instruments, which represents the most cost-effective solution for applications where low voltage operation is needed. The output of the LMV321 OpAmp has a stable unity-gain, acting as a buffer so that the host MCU can sample the output voltage of the INA250 via the AN pin of the mikroBUS™ socket.

The INA250 can be configured to measure both unidirectional and bidirectional currents through the reference voltage level. For unidirectional operation, the reference pin should be tied to the ground. When the current increases, the output signal also increases upwards from this reference voltage (or ground in this case). For bidirectional currents, an external voltage source can be used as the reference voltage, in this case, a low dropout linear regulator AP7331 from Diodes Incorporated to provide the 2.5V reference supply voltage for the INA250. The reference voltage level can be selected by positioning the SMD jumper labeled VREF SEL to an appropriate position choosing between 2.5V provided by AP7331 or GND.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it allows both 3.3V and 5V capable MCUs to 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.