This is the compact version of a simple carrier for Allegro’s ACS37200LLXTR-100B5 Hall effect-based, electrically isolated current sensor that offers an extra-low-resistance (~0.05 mΩ) IC current path, a 150 kHz bandwidth with <4 µs response time, 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 ACS37200 Hall effect-based, electrically isolated current sensors with user-configurable overcurrent fault output; we therefore recommend careful reading of the ACS37200 datasheet (1MB pdf) 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 primary current path resistance of 0.05 mΩ in the sensor IC 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.
• 150 kHz bandwitdth 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.
• VREF output for pseudo-differential signaling in noisy application environments.
• 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 board includes routed slots for increased creepage along the PCB surface and offers a variety of ways to insert it into the current path along with 0.1″-pitch (breadboard-compatible) power, ground, and output pins.
• Optional connection points for convenient 4-wire measurement of the IC current path resistance.

The connection points and the direction interpreted as positive current flow (via the +i arrow) are labeled on the silkscreen.

Details for item #5783

ACS37200LLXTR-100B5 Current Sensor Compact Carrier -100A to +100A, 5V, bottom view                                         ACS37200 Current Sensor Compact Carrier.

This compact carrier features the ACS37200LLXTR-100B5, which is intended for nominal 5 V operation and is designed for bidirectional input current from -100 A to +100 A. This version can be visually distinguished from the other versions by the “10B5” 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 (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 20 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage:

VOUT=2.5V+0.02VA⋅IP

IP=VOUT–2.5V0.02VA=(VOUT–2.5V)⋅50AV

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

The zero-current reference voltage, which is available on VREF, can be used to reduce errors due to reference shifts or noise on the ground line.

The carrier board also includes two optional connection points, marked in red in the picture above, for taking a 4-wire measurement of the IC current path resistance. This is to more conveniently evaluate that property of the chip and is not required for normal use of this product as a current sensor.

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.

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).

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. The largest through-holes are big enough for 8 AWG wires or #8 or M4 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 are generally not suitable for high currents and could limit the usable range of the sensor. The pictures below show examples of various connection options with the CT432/CT433 compact carrier, which has the same physical dimensions as the ACS37200 compact carrier.

Isolation rating and board creepage considerations

The ACS37200 has a manufacturer-rated basic working isolation voltage of 1097 VRMS. The IC package has a creepage of 8 mm, and our carrier PCB has a routed slot under the IC to provide a PCB creepage distance of 10.1 mm. A rough rule of thumb is that uncontaminated FR4 PCBs should have roughly 1 mm of creepage per 100 VRMS of isolation. Please note that these carrier boards are not certified to any particular safety standard.

Warning: This product is generally intended for use below 30 V, and many of the application example pictures (e.g. use on a breadboard) are appropriate for such lower-voltage applications. These boards can be used at higher voltages, but 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

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 ACS37200 can measure up to ±200 A. However, the sensor chip can overheat at lower currents. In our tests, we found that our ACS37200 compact carrier boards 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, as can switching to the equivalent large carrier version.

Warning: Exceeding temperature or current limits can cause permanent damage to the sensor. If you are measuring an average continuous current greater than 40 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.

Dimensions:

• Size : 0.8″ × 1.1″
• Weight : 2.1 g

Specifications

• Typical operating voltage : 5 V
• Current sense : 20 mV/A
• Minimum logic voltage : 4.5 V
• Maximum logic voltage : 5.5 V
• Supply current : 20 mA1
• Current range : -100A to +100A (bidirectional 100A), 5V
• Current sensor : Allegro ACS37200LLXTR-100B5

Documentation:

• downloadable PDF (358k pdf).

Package Includes:

• 1 x Pololu 5783 ACS37200LLXTR-100B5 Current Sensor Compact Carrier -100A to +100A, 5V