Hall Current 6 Click is a very accurate current measurement Click board™, based on the ACS723 IC. This IC is a galvanically isolated current sensor, which utilizes the Hall-effect principle. Its most distinctive feature is its very low series resistance of only 0.65 mΩ, which makes this device a nearly-perfect ammeter. The maximum current which can be measured with Hall Current 6 Click ranges from -5 A to +5 A, with the optimized precision. It features a dedicated bandwidth selection pin, which allows better noise performance for a specific application.
Hall Current 6 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.
The ACS723 has a precisely trimmed analog output, which changes linearly with the applied current. Its accuracy is further optimized through the Allegro’s patented digital temperature compensation. Its excellent galvanic isolation simplifies the application, allowing the Click board™ to be connected directly to the high side of the measured circuit. It can be used to measure both DC and AC current. The ACS723 IC features a bandwidth selection pin, used to adjust the measurement to a frequency bandwidth of the application. Hall Current 6 Click can be used in motor control applications, load detection and management applications, switch-mode power supplies, overcurrent fault protection applications, and similar applications that require accurate and reliable current sensing.
Note: The Click board™ is to be used by trained personnel only, while applying high voltages. A special care should be taken when working with hazardous voltage levels.
Hall Current 6 utilizes the ACS723(LLCTR-05AB-T), a high-accuracy, galvanically isolated current sensor IC, from Allegro Microsystems. This sensor utilizes the Hall effect phenomenon to measure the current passing through the internally fused input pins of the IC. This allows the series resistance to stay very low. Current through the input rails of the IC generates a magnetic field, causing the Hall effect on the current through the integrated sensor. These two current circuits are completely isolated, with the basic isolation working voltage of about 297VRMS, allowing the Click board™ to be used in high-side current sensing applications.
The output voltage changes linearly with the current in the primary circuit, with the ratio of 400mV/A, and it is fed to the MCP3221, a 12-bit analog to digital converter (ADC) with I2C interface, from Microchip. This is a well-established converter used in many Click board™ designs, thanks to its proven reliability, reasonably good sampling rate well suited for instrumentation applications (22.3 ksps), and simplicity of use. It converts the output voltage from the ACS723 into a digital value, which is available over the I2C interface. The output voltage of the ACS723 has a very linear dependency of the current through the primary pins, due to the Allegro’s patented digital temperature compensation. Although it can be used in a rather limited current range of ±5A, it has a great accuracy of ±3% (referred to as a Total Output Error in the datasheet).
The ACS723 IC features a bandwidth selection pin, which allows the bandwidth selection according to the application it is used in. For example, when measuring current in some applications that operate at lower frequencies, limiting the bandwidth improves the noise performance, enabling to obtain results with higher accuracy. The bandwidth selection pin acts as a filter on the measurement line, allowing two cutoff frequencies: 20kHz and 80kHz. The BW_SEL pin of the ACS723 is routed to the small SMD jumper, labeled as BW SEL. When the jumper is at the position 0, the bandwidth of the device is 80kHz.
The secondary side of the ACS733 is powered from the 5V mikroBUS™ rail. As explained earlier, current flowing through the primary conductors is galvanically isolated from the rest of the IC, protecting low-voltage parts of the Click board™, as well as the host MCU. The Click board™ should be connected in series with the load through which the current is measured, by using the load connector, labeled with IP+ and IP-. A very low internal resistance of only 0.65 mΩ across the primary conductors, will not disturb the current through the circuit, so the Click board™ will not introduce its own error into the measurement, thus acting as a nearly-perfect ammeter.
The voltage at which the I2C lines are pulled up can be selected using the VCC SEL jumper. The ability to select the logic voltage level allows this Click board™ to be interfaced with a wide range of different MCUs, operating at both 3.3V and 5V.
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