ACS71240KEXBLT-030B3 Current Sensor Carrier -30A to +30A, 3.3V

Overview

We are offering these breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS71240 Hall effect-based, electrically isolated current sensors with overcurrent fault output; we therefore recommend careful reading of the ACS71240 datasheet before using this product. The following list details some of the sensor’s key features:

• Hall effect-based sensor with electrically isolated current path allows the sensor to be inserted anywhere along the current path and to be used in applications that require electrical isolation.
• Differential Hall sensing rejects common-mode fields, so the orientation of the sensor relative to uniform external magnetic fields (e.g. the Earth’s magnetic field) has less effect on the measurement.
• The conductive path internal resistance is typically 0.6 mΩ, and the PCB is made with 2-oz copper, so very little power is lost in the module.
• High-bandwidth 120 kHz analog output voltage proportional to AC or DC currents.
• Less than 5 µs response time.
• Output is not ratiometric (i.e. the zero point and sensitivity are independent of the actual supply voltage), which provides immunity from noisy supplies.
• Overcurrent fault output with 1.5 µs response time indicates when the current exceeds the optimized sensing range and can be used for fast short-circuit detection.
• Integrated digital temperature compensation circuitry allows for near closed loop accuracy over temperature in an open loop sensor.
• Automotive-grade operating temperature range of -40°C to 125°C.
• 0.7″×0.8″ carrier board offers a variety of ways to insert it into the current path along with 0.1″-pitch (breadboard-compatible) power, ground, and output pins.
• 3.3V and 5V versions available.
• Unidirectional and bidirectional versions available.

The pads are labeled on the bottom silkscreen. The silkscreen also shows the direction that is interpreted as positive current flow via the +i arrow.

Details for item #5241

ACS71240KEXBLT-030B3 Current Sensor Carrier -30A to +30A, 3.3V, bottom view.

ACS71240 Current Sensor Carrier.

This carrier features the ACS71240KEXBLT-030B3, which is intended for operation around 3.3 V and is designed for bidirectional input current from -30 A to +30 A. This version can be visually distinguished from the other versions by the “3V3 B30” printed on the bottom side, as shown in the left picture above.

Part Suffix	Range	Supply Voltage	Sensitivity	Zero Point	Fault Trip Level
030B3	±30 A (bidirectional)	3.0 V to 3.6 V	44 mV/A	1.65 V	±30 A

Using the sensor

This sensor has five required connections: the input current (IP+ and IP-), logic power (VCC and GND), and the sensor output (VIOUT).

The sensor requires a supply voltage of 3.0 V to 3.6 V to be connected across the VCC and GND pads, which are labeled on the bottom silkscreen. The sensor outputs an analog voltage on VIOUT that is centered at 1.65 V and changes by 44 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage:

``V_"IOUT" = 1.65 text(V) + 0.044 text(V)/text(A) * I_"P"``

``I_"P" = (V_"IOUT" – 1.65 text(V)) / (0.044 text(V)/text(A)) = (V_"IOUT" – 1.65 text(V)) * 22.7 text(A)/text(V)``

The output is not ratiometric, so the zero point and sensitivity are independent of the actual supply voltage.

The optional FAULT pin is normally at VCC and is pulled low when the IP current magnitude exceeds 30 A in either direction. This pin only asserts while the fault condition is present (it is not latched).

The FAULT, VIOUT, VCC, and GND pins work with 0.1″-pitch header pins and are compatible with standard solderless breadboards.

You can insert the board into your current path in a variety of ways. Holes with 0.1″, 3.5 mm, and 5 mm spacing are available as shown in the diagram above for connecting male header pins or terminal blocks. For high-current applications, you can solder wires directly to the through-holes that best match your wires, or you can use solderless ring terminal connectors. The largest through-holes are big enough for 8 AWG wires or #6 or M3.5 screws, and the second-largest through-holes (and mounting holes) are sized for 12 AWG wires or #2 or M2 screws. The pictures below show some of the possible connection options:

Warning: This product is intended for use below 30 V. Working with higher voltages can be extremely dangerous and should only be attempted by qualified individuals with appropriate equipment and experience.

Schematic and dimension diagrams

ACS72140 current sensor carrier schematic diagram.

The dimension diagram is available as a downloadable PDF (274k pdf).

Real-world power dissipation considerations

Thermal image of a high-current test of a Pololu current sensor carrier (not necessarily this product).

Depending on the version, the ACS71240 can measure up to ±50 A. However, the sensor chip will typically overheat at lower currents. In our tests, we found that our ACS71240 carrier board could conduct about 45 A continuously without reaching the thermal limit for the IC. Our tests were conducted at approximately 25°C ambient temperature with no forced air flow.

The actual current you can pass through the sensor will depend on how well you can keep it cool. The carrier’s printed circuit board is designed to help with this by drawing heat out of the sensor chip. Solid connections to the current path pins (such as with thick soldered wires or large, tightly-secured lugs) can also help reduce heat build-up in the sensor and carrier board.

Warning: Exceeding temperature or current limits can cause permanent damage to the sensor. If you are measuring an average continuous current greater than 30 A, we strongly recommend that you monitor the sensor’s temperature and look into additional cooling if necessary.

This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it.

Comparison of the Pololu current sensor carriers

We have a variety of current sensors available with different ranges, sensitivities, and features. The table below summarizes our selection of active and preferred options:

You can also use the following selection box to see all these options sorted by current range:

Alternatives available with variations in these parameter(s): current range Select variant…