ACS72981LLRATR-050B3 Current Sensor Compact Carrier -50A to +50A, 3.3V

Overview

We are offering these compact breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS72981xLR Hall effect-based linear current sensors; we therefore recommend careful reading of the ACS72981 datasheet before using this product. The following list details some of the sensor’s key features:

• 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 0.2 mΩ, and the PCB is made with 6 layers of 2-oz copper, so very little power is lost in the module.
• Use of a Hall effect sensor means the IC is able to electrically isolate the current path from the sensor’s electronics, which allows the sensor to be inserted anywhere along the current path and to be used in applications that require electrical isolation.
• High-bandwidth 250 kHz analogue output voltage proportional to AC or DC currents.
• Less than 2 µs response time.
• 3.3V and 5V versions available.
• Integrated digital temperature compensation circuitry allows improved accuracy over the full operating temperature range.

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

Details for item #5250

This carrier features the ACS72981LLRATR-050B3, which is intended for nominal 3.3 V operation and is designed for bidirectional input current from -50 A to +50 A. This version can be visually distinguished from the other versions by the “3V3 B05” printed on the bottom side, as shown in the left picture above.

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 labelled on the bottom silkscreen. The sensor outputs a ratiometric analogue voltage on VIOUT that is centred at VCC/2 and changes by 26.4 mV × (VCC/3.3 V) per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage:

``text(VIOUT) = text(VCC) / 2 + 0.0264 V/A * text(VCC) / (3.3 V) * text(IP) = text(VCC) * (1/2 + text(IP) / (125 A))``

``text(IP) = 125A * (text(VIOUT) / text(VCC) – 1/2)``

The 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. For typical 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, as shown in the picture above. 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. Holes with 0.1″, 3.5 mm, and 5 mm spacing are also available as shown in the diagram above for connecting male header pins or terminal blocks, but please note that these connection options will generally not be suitable for the kinds of currents this sensor is intended for.

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 protective gear.

Schematic and dimension diagrams

The dimension diagram is available as a downloadable PDF (264k pdf).

Dimensions

General specifications

Identifying markings

Notes:

1

At VCC = 3.3 V.

2

Typical.

File downloads

• Dimension diagram of the ACS72981xLR Current Sensor Compact Carriers (264k pdf)

• 3D model of the ACS72981xLR Current Sensor Compact Carriers (3MB step)

• Drill guide for the ACS72981xLR Current Sensor Carriers (18k dxf)

  This DXF drawing shows the locations of all of the board’s holes.

Recommended links

• ACS72981 datasheet

• Allegro Application Note AN296169: Characterizing System Bandwidth in Complex Current Sensor Applications

  This is the application note referenced on page 16 of the ACS724 datasheet, page 22 of the ACS71240 datasheet, and page 42 of the ACS72981xLR datasheet. The ACS720 is used validate the test methods presented, but these same methods and principles would also apply to the ACS724, ACS71240, and ACS72981.

• Allegro product page for the ACS72981 Hall-based Current Sensor

  Allegro product page for the ACS72981, where you can find additional application notes and other resources.