This is the compact version of a simple carrier for Allegro’s ACS37220LEZATR-200B5 Hall effect-based, electrically isolated current sensor, which offers an extra-low-resistance (~0.1 mΩ) current path, a high 150 kHz bandwidth for fast response times, and an overcurrent fault output with a user-configurable threshold.

We are offering these breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS37220 Hall effect-based, electrically isolated current sensors with user-configurable overcurrent fault output; we therefore recommend careful reading of the  ACS37220 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.
• Extra-low IC primary current path resistance of 0.1 mΩ for higher efficiency.
• 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.
• High-bandwidth 150 kHz analog output voltage proportional to AC or DC currents.
• Less than 4 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.
• User-configurable overcurrent fault output with 3 µs response time indicates when the current magnitude exceeds the set threshold and can be used for fast short-circuit detection.
• Integrated digital temperature compensation circuitry allows improved accuracy over the full operating temperature range.
• Automotive-grade operating temperature range of -40°C to 150°C.
• Carrier boards, available in compact and large sizes, offer a variety of ways to insert it into the current path and 0.1″-pitch (breadboard compatible) power, ground, and output pins.
• The PCB is made with 2-layer (compact versions) or 6-layer (large versions) 2-oz copper, so very little power is lost in the module.
• 3.3V and 5V versions available.

The connection points are labeled on the silkscreen, which is on the bottom side of the compact versions and on both sides of the large versions. The bottom silkscreen also shows the direction that is interpreted as positive current flow via the +i arrow.

Details for item #5294

This compact carrier features the ACS37220LEZATR-200B5, which is intended for nominal 5 V operation and is designed for bidirectional input current from -200 A to +200 A. This version can be visually distinguished from the other versions by the “5V B20” printed on the bottom side, as shown in the left picture above.

A larger carrier with a 6-layer PCB is also available for this sensor IC with room for larger connectors and thicker wires for the high-current path, offering different ways to use or evaluate this current sensor.

Using the sensor

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

The sensor requires a supply voltage of 4.5 V to 5.5 V to be connected across the VDD and GND pads, which are labeled on the bottom silkscreen. The sensor outputs an analog voltage on VOUT that is centered at 2.5 V and changes by 10 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage:

• VOUT=2.5V+0.010VA⋅IP
• IP=VOUT–2.5V0.010VA=(VOUT–2.5V)⋅100AV

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

Setting the overcurrent fault threshold

The optional VOC pin can be used to set the overcurrent fault threshold. An on-board 205 kΩ resistor between VOC and GND sets the default overcurrent fault threshold to approximately 200% of the nominal sensing range, and an external resistor can be added in parallel between VOC and GND to lower this threshold to between 50% and 200%. The following equation gives the value of this parallel resistor, ROC, in kΩ as a function of overcurrent fault threshold percentage P:

• ROC=205kΩ⋅P205%–P

So for example, to set the overcurrent fault limit to 50% of the nominal sensing range, a 66 kΩ external resistor can be added between VOC and GND:

• ROC=205kΩ⋅50%205%–50%≈66kΩ

As a shortcut, VOC can be connected directly to ground to set the overcurrent fault limit to 100% of the nominal sensing range.

Alternatively, the on-board resistor can be replaced, or a low-impedance voltage source can be applied directly to the VOC pin as described in the  ACS37220 datasheet.

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

We manufacture these boards in-house at our Las Vegas facility, which gives us the flexibility to make these current sensors with custom default overcurrent fault thresholds. If you are interested in customization, please contact us.

Making connections to the board

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 pictures below. The largest through-holes are big enough for 10 AWG wires or #6 or M3.5 screws, and the second-largest through-holes (and mounting holes) are sized for 14 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 high currents intended for this sensor.

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.