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

Overview

ACS72981 Current Sensor Compact Carrier (top) and Large Carrier (bottom) size comparison.

We are offering these breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS72981xLR Hall effect-based, electrically isolated 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:

• 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 0.2 mΩ, and the PCB is made with 6 layers of 2-oz copper, so very little power is lost in the module.
• High-bandwidth 250 kHz analog output voltage proportional to AC or DC currents
• Less than 2 µs response time.
• Integrated digital temperature compensation circuitry allows improved accuracy over the full operating temperature range.
• Carrier boards, available in compact and large sizes, offer 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 connection points are labeled on the bottom silkscreen. The silkscreen also shows the direction that is interpreted as positive current flow via the +i arrow.

The following table lists the available ACS72981 carrier options:

	Pololu Item #	Part Suffix	Supply Voltage (V)	Current Range		Sensitivity @ Nominal Vcc (mV/A)	Zero Point @ Nominal Vcc (V)	Size	Price
Large Carrier	#5270	050B3	3.0 to 3.6 (3.3 nominal)	Bidirectional	±50 A	26.4	1.65	1.4″×1.2″	$12.95
	#5273	100B3			±100 A	13.2
	#5277	150B3			±150 A	8.8
	#5281	200B3			±200 A	6.6
	#5272	050U3		Unidirectional	0-50 A	52.8	0.33
	#5275	100U3			0-100 A	26.4
	#5279	150U3			0-150 A	17.6
	#5283	200U3			0-200 A	13.2
	#5271	050B5	4.5 to 5.5 (5 nominal)	Bidirectional	±50 A	40	2.5
	#5274	100B5			±100 A	20
	#5278	150B5			±150 A	13.3
	#5282	200B5			±200 A	10
	#5276	100U5		Unidirectional	0-100 A	40	0.5
	#5280	150U5			0-150 A	26.7
Compact Carrier	#5250	050B3	3.0 to 3.6 (3.3 nominal)	Bidirectional	±50 A	26.4	1.65	0.7″×0.8″	$9.95
	#5253	100B3			±100 A	13.2
	#5257	150B3			±150 A	8.8
	#5261	200B3			±200 A	6.6
	#5252	050U3		Unidirectional	0-50 A	52.8	0.33
	#5255	100U3			0-100 A	26.4
	#5259	150U3			0-150 A	17.6
	#5263	200U3			0-200 A	13.2
	#5251	050B5	4.5 to 5.5 (5 nominal)	Bidirectional	±50 A	40	2.5
	#5254	100B5			±100 A	20
	#5258	150B5			±150 A	13.3
	#5262	200B5			±200 A	10
	#5256	100U5		Unidirectional	0-100 A	40	0.5
	#5260	150U5			0-150 A	26.7

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

Details for item #5270

ACS72981LLRATR-050B3 Current Sensor Large Carrier -50A to +50A, 3.3V, bottom view.

ACS72981 Current Sensor Large Carrier.

This large 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.

Part Suffix	Range	Supply Voltage	Sensitivity @ 3.3 V	Zero Point @ 3.3 V	Size
050B3	±50 A (bidirectional)	3.0 V to 3.6 V	26.4 mV/A	1.65 V	1.4″×1.2″

A compact carrier is also available for this sensor IC for more space-constrained applications or to evaluate the IC’s performance with a smaller PCB area for thermal dissipation.

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 a ratiometric analog voltage on VIOUT that is centered 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:

``V_"IOUT" = V_"CC" / 2 + 0.0264 text(V)/text(A) * V_"CC" / (3.3 text(V)) * I_"P" = V_"CC" * (1/2 + I_"P" / (125 text(A)))``

``I_"P" = 125 text(A) * (V_"IOUT" / V_"CC" – 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. The largest through-holes are 8.4 mm in diameter with 20 mm spacing. These can be used with 5/16″ or M8 screws for attaching various types of lugs or solderless ring terminals, or thick wires up to 2 AWG can be soldered directly to the board. The slots near the edge of the board can accommodate a 4-pin terminal block or other connector with a pitch between 7.5 mm and 9.5 mm. Examples of these kinds of connections are shown in the pictures below. Holes with 0.1″, 3.5 mm, and 5 mm spacing are also available for connecting male header pins or terminal blocks, but please note that these smaller connection options are generally not suitable for high currents like those 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 experience.

Schematic and dimension diagrams

ACS72981 Current Sensor Carrier schematic diagram.

The dimension diagram is available as a downloadable PDF (400k 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 ACS72981 can measure up to ±200 A, but its datasheet specifies an absolute maximum continuous current of 120 A. Furthermore, the sensor chip can overheat at lower currents. In our tests, we found that our ACS72981 carrier boards could conduct 60 A continuously while staying well below 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 50 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…