ACS724 Current Sensor Carrier -2.5A to +2.5A

Pololu are offering these breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS724LLCTR Hall effect-based, electrically isolated current sensors; Pololu therefore recommend careful reading of the ACS724 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 1.2 mO, and the PCB is made with 2-oz or 4-oz copper, depending on the sensor version, so very little power is lost in the module.
• High-bandwidth 120 kHz analog output voltage proportional to AC or DC currents.
• Typical 4 µs response time.
• Optional FILTER pin simplifies bandwidth limiting for better noise reduction and improved resolution at lower frequencies.
• 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 150°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.
• Unidirectional and bidirectional versions available.

The pads are labeled on the bottom silkscreen, as shown in the picture to the right. The silkscreen also shows the direction that is interpreted as positive current flow via the +i arrow.

A variety of options are available with different current sensing ranges and sensitivities:

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

These versions all look very similar, and while you can distinguish them by reading the text on the IC, Pololu also provide a white box on the bottom silkscreen where you can add your own distinguishing markings if so desired.

Details for item #4040

ACS724LLCTR-2P5AB Current Sensor Carrier -2.5A to +2.5A, top view.

ACS724LLCTR-2P5AB Current Sensor Carrier -2.5A to +2.5A with included 0.1" header pins.

This carrier features the ACS724LLCTR-2P5AB, which operates at 5 V and is designed for bidirectional input current from -2.5 A to +2.5 A. This version can be visually distinguished from the other versions by the writing on the IC as shown in the pictures above.

When Vcc is 5 V, the output voltage is centered at 2.5 V and changes by 800 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage. More generally, the sensor’s zero point and sensitivity depend on VCC as follows:

Zero Point=VCC2" role="presentation" style="position: relative;">Zero Point=VCC2$\text{Zero Point}=\frac{V_{\text{CC}}}{2}$

Sensitivity=0.8VA⋅(1+(VCC–5V)⋅1.35V)" role="presentation" style="position: relative;">Sensitivity=0.8VA·(1+(VCC–5V)·1.35V)$\text{Sensitivity}=0.8\frac{\text{V}}{\text{A}}·(1+\frac{(V_{\text{CC}}–5\text{V})·1.3}{5\text{V}})$

This board ships assembled with all surface mount components, and a 3×1 strip of 0.1" header pins is included but not soldered in.

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 4.5 V to 5.5 V to be connected across the VCC and GND pads, which are labeled on the bottom silkscreen, and the sensor outputs an analog voltage with a linear relationship to the input current:

VIOUT=Zero Point+Sensitivity⋅IP" role="presentation" style="position: relative;">VIOUT=Zero Point+Sensitivity·IP$V_{\text{IOUT}}=\text{Zero Point}+\text{Sensitivity}·I_{\text{P}}$

IP=VIOUT–Zero PointSensitivity" role="presentation" style="position: relative;">IP=VIOUT–Zero PointSensitivity$I_{\text{P}}=\frac{V_{\text{IOUT}}–\text{Zero Point}}{\text{Sensitivity}}$

The FILTER pin lets you adjust the board’s bandwidth by adding a capacitor to ground (a ground pad has been added next to the FILTER pin for convenience) in parallel with the 1 nF capacitor that is already on the board. Without an added external filter capacitor, the bandwidth is about 90 kHz. The datasheet provides more information on how the filter capacitors affect bandwidth.

You can insert the board into your current path in a variety of ways. For low-current applications, you can solder 0.1" male header pins to the board via the smallest pair of through-holes on the input-current side of the board. For higher-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.

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

Schematic diagram of the ACS724 Current Sensor Carrier.

The dimension diagram is available as a downloadable PDF (1MB pdf).

Comparison of the Pololu current sensor carriers

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

	ACS711 Current Sensor Carriers	ACS71240 Current Sensor Carriers	ACS724 Current Sensor Carriers	ACS37220 Current Sensor Compact Carriers	ACS37220 Current Sensor Large Carriers	ACS72981 Current Sensor Compact Carriers	ACS72981 Current Sensor Large Carriers	CT432/CT433 TMR Current Sensor Compact Carriers	CT432/CT433 TMR Current Sensor Large Carriers
Sensor IC	Allegro ACS711KEXT	Allegro ACS71240	Allegro ACS724LLCTR	Allegro ACS37220		Allegro ACS72981xLR		Allegro CT432/CT433
Sensing technology	Hall effect	Hall effect	Hall effect	Hall effect		Hall effect		XtremeSense™ TMR (tunneling magnetoresistance)
Logic voltage range (V)	3.0–5.5	3.3V versions: 3.0–3.6 5V versions: 4.5–5.5	4.5–5.5	3.3V versions: 3.15–3.45 5V versions: 4.5–5.5		3.3V versions: 3.0–3.6 5V versions: 4.5–5.5		3.3V versions: 3.0–3.6 5V versions: 4.75–5.5
Current range / sensitivity	Bidirectional:(1) ±15.5 A / 90 mV/A ±31 A / 45 mV/A	3.3V Bidirectional: ±10 A / 132 mV/A ±30 A / 44 mV/A ±50 A / 26.4 mV/A 5V Bidirectional: ±10 A / 200 mV/A ±30 A / 66 mV/A ±50 A / 40 mV/A 5V Unidirectional: 0–?50 A / 80 mv/A	5V Bidirectional:(2) ±2.5 A / 800 mV/A ±5 A / 400 mV/A ±10 A / 200 mV/A ±20 A / 100 mV/A ±30 A / 66 mV/A ±50 A / 40 mV/A 5V Unidirectional:(2) 0–?5 A / 800 mv/A 0–?10 A / 400 mv/A 0–?20 A / 200 mv/A 0–?30 A / 133 mV/A	3.3V Bidirectional: ±100 A / 13.2 mV/A ±150 A / 8.8 mV/A 5V Bidirectional: ±100 A / 20 mV/A ±150 A / 13.3 mV/A ±200 A / 10 mV/A	3.3V Bidirectional: ±100 A / 13.2 mV/A ±150 A / 8.8 mV/A 5V Bidirectional: ±100 A / 20 mV/A ±150 A / 13.3 mV/A ±200 A / 10 mV/A	3.3V Bidirectional:(1) ±50 A / 26.4 mV/A ±100 A / 13.2 mV/A ±150 A / 8.8 mV/A 3.3V Unidirectional:(1) 0–?50 A / 52.8 mv/A 0–?100 A / 26.4 mv/A 0–?150 A / 17.6 mv/A 0–?200 A / 13.2 mv/A 5V Bidirectional:(2) ±50 A / 40 mV/A ±100 A / 20 mV/A ±150 A / 13.3 mV/A ±200 A / 10 mV/A 5V Unidirectional:(2) 0–?100 A / 40 mv/A 0–?150 A / 26.7 mv/A	3.3V Bidirectional:(1) ±50 A / 26.4 mV/A ±100 A / 13.2 mV/A ±150 A / 8.8 mV/A 3.3V Unidirectional:(1) 0–?50 A / 52.8 mv/A 0–?100 A / 26.4 mv/A 0–?150 A / 17.6 mv/A 0–?200 A / 13.2 mv/A 5V Bidirectional:(2) ±50 A / 40 mV/A ±100 A / 20 mV/A ±150 A / 13.3 mV/A ±200 A / 10 mV/A 5V Unidirectional:(2) 0–?100 A / 40 mv/A 0–?150 A / 26.7 mv/A	3.3V Bidirectional: ±20 A / 50 mV/A ±30 A / 33.3 mV/A ±50 A / 20 mV/A 5V Bidirectional: ±20 A / 100 mV/A ±30 A / 66.7 mV/A ±65 A / 30.8 mV/A 5V Unidirectional: 0–?50 A / 80 mv/A 0–?70 A / 57.1 mv/A	3.3V Bidirectional: ±50 A / 20 mV/A 5V Bidirectional: ±65 A / 30.8 mV/A 5V Unidirectional: 0–?50 A / 80 mv/A 0–?70 A / 57.1 mv/A
IC path resistance	0.6 mO	0.6 mO	0.6 mO	0.1 mO		0.2 mO		1 mO
PCB	2 layers, 2-oz copper	2 layers, 2-oz copper	2 layers, 2- or 4-oz copper(4)	2 layers, 2-oz copper	6 layers, 2-oz copper	6 layers, 2-oz copper	6 layers, 2-oz copper	2 or 4 layers(5), 2-oz copper	6 layers, 2-oz copper
Max bandwidth	100 kHz	120 kHz	120 kHz(3)	150 kHz		250 kHz		1 MHz
Size	0.7" × 0.8"	0.7" × 0.8"	0.7" × 0.8"	0.7" × 0.8"	1.4" × 1.2"	0.7" × 0.8"	1.4" × 1.2"	0.8" × 1.1"	1.4" × 1.2"
Overcurrent fault output				User-configurable threshold
Common-mode field rejection
Non-ratiometric output

⁽¹⁾ Sensitivity when Vcc = 3.3 V; sensitivity is ratiometric.
⁽²⁾ Sensitivity when Vcc = 5 V; sensitivity is ratiometric.
⁽³⁾ Bandwidth can be reduced by adding a filter capacitor.
⁽⁴⁾ ±50A version uses 4-oz copper PCB; all other versions use 2-oz copper.
⁽⁵⁾ 50A and higher versions use 4-layer PCB; all other versions use 2-layer PCB.

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 rangeSelect variant…

Dimensions

General specifications

Identifying markings

Notes:

1

When Vcc is 5 V.

2

Max. 10 mA typical.

File downloads

• Dimension diagram of the ACS724 Current Sensor Carrier (1MB pdf)

• 3D model of the ACS724 Current Sensor Carrier (3MB step)

• Drill guide for ACHS-712x Current Sensor Carriers (17k dxf)

  This DXF drawing shows the locations of all of the board’s holes. The through-hole sizes and locations in this file also apply to cs01b versions of the PCB, though some of the via locations are different.

Recommended links

• ACS724 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 ACS724 Hall-based Current Sensor

  Allegro product page for the ACS724, where you can find additional application notes and other resources.