This is the compact version of a simple carrier for Allegro’s ACS37030LMYATR-065B3 electrically isolated current sensor that uses two signal paths—Hall effect and inductive coil—to capture both low-frequency and high-frequency information. This allows for a DC through 5 MHz bandwidth and typical response times of 40 ns.

We are offering these breakout boards with support from Allegro Microsystems as an easy way to use or evaluate their ACS37030 DC to 5 MHz bandwidth, galvanically isolated, high-accuracy current sensors with reference output; we therefore recommend careful reading of the ACS37030 datasheet (2MB pdf) before using this product. The following list details some of the sensor’s key features:

• 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.
• High bandwidth (DC to 5 MHz) analog voltage output proportional to the current.
• 40 ns typical response time.
• Two current signal paths:
• Hall effect-based sensor for capturing DC and low-frequency current information
• Inductive coil for capturing high-frequency current information.
• 0.7 mΩ (LZ package) or 0.9 mΩ (MY package) primary current path resistance in the sensor IC, and 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.
• 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.
• Output is not ratiometric (i.e. the zero point and sensitivity are independent of the actual supply voltage), which provides immunity from noisy supplies.
• 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 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.
• ACS37030MY ICs have a higher isolation rating and creepage/clearance distance than the ACS37030LZ ICs and are on PCBs with routed slots for maximum benefit from that higher creepage.
• ACS37030MY carriers have optional connection points for convenient 4-wire measurement of the IC current path resistance.

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 #5696

                                                                        

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 3.0 V to 3.6 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 1.65 V and changes by 20.3 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage:

VOUT=1.65V+0.0203VA⋅IP

IP=VOUT–1.65V0.0203VA=(VOUT–1.65V)⋅49.3AV

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.

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 ACS37030MY compact carrier.

Isolation rating and board creepage considerations

The ACS37030LLZ and ACS37030LMY differ in their manufacturer-rated isolation voltages of 840 VRMS and 1000 VRMS, respectively. The PCB creepage on the ACS37030LLZ carriers is 4.1 mm, which is the same as the creepage on the LZ IC package itself. The MY IC package has a wider body with a creepage of 8.5 mm, and our ACS37030LMY compact carrier PCB has a routed slot under the IC that increases the PCB creepage to 11.7 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

Documents:

• downloadable PDF (649k 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 ACS37030 can measure up to ±65 A. However, the sensor chip can overheat at lower currents. In our tests, we found that our ACS37030MY compact carrier boards could conduct about 35 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 25 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.

Specifications:

• Typical operating voltage : 3.3 V
• Current sense : 20.3 mV/A
• Minimum logic voltage : 3.0 V
• Maximum logic voltage : 3.6 V
• Package : MY
• Working isolation voltage : 1000 VRMS1
• Supply current : 20 mA2
• Current range : -​65A to +65A (bidirectional 65A), 3.3V
• Current sensor :Allegro ACS37030LMYATR-065B3

Package Includes:

• 1 x Pololu 5696 ACS37030LMYATR-065B3 Current Sensor Compact Carrier -65A to +65A, 3.3V