New Current-Sensor ICs Check the Pulse of Power Electronics

Oct. 13, 2023

Can current-sensor ICs win out against the shunt resistor and other passive components? Check out some of the latest offerings on the market in this Products of the Week gallery.

James Morra

Related To: Electronic Design

Current-Sensor IC Carefully Handles High Currents in EVs

At high power levels, it’s increasingly not ideal to use shunt resistors paired with op amps or other passive components for current sensing. The fundamental problem with any shunt resistor is that it’s a resistor and thus experiences larger power losses as the current traveling through it rises. Such devices can also be impacted by parasitic inductance when the resistance is reduced, causing delays in turn-on and turn-off and raising the risk of voltage spikes.

As a result, Hall-effect and other “non-contact” current-sensor ICs are becoming more widely used. Hall-based current sensors take advantage of the fact that the copper wires on a circuit board, and any other conductor with current cascading through it, has a proportional magnetic field produced around it. By measuring the magnetic field, the current that generated it—up to thousands of amps of AC or DC current—can be measured. And unlike shunt resistors, the impact on the current being measured is minimal.

Hall-based current-sensor ICs can be placed directly in the path of the load, measuring the current as it passes through the IC package. They can also be placed above the conductor and sense current through proximity.

On that front, the ACS37601 is the latest programmable linear Hall-effect current sensor IC from Allegro Microsystems. Rated for ASIL C functional safety, it’s designed to deliver the high precision required for EV traction and auxiliary power inverters as well as battery-management systems (BMS). Relatively high operating bandwidth of up to 240 kHz and fast response times (200 ns) help it detect transient events and handle high-frequency switching.

The core-based current-sensor IC can accurately measure current traveling through EV power subsystems that operate at more than 200 A to within 0.8% over the automotive temperature range of −40 to 150°C, while offering output voltage offset of under 5 mV. The programmable overtemperature and overcurrent pin give the ultra-thin four-pin package additional protection against short circuits. According to Allegro, other improvements under the hood result in a 30% reduction in noise relative to existing current sensors.

While a dedicated bias power supply is required for these types of current-monitoring ICs, Allegro said the ACS37601 supports 3.3- or 5-V input voltages, enabling the use of the most advanced microprocessors.

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For any electronic control system, current sensing is one of the most important forms of performance feedback. Whether the current measurements are used for real-time protection (against short circuits and other surges of current), control loops (e.g., peak-current mode or average-current mode control in power electronics), or power management (e.g., charging and discharging high-voltage battery packs), understanding the ins and outs of the current traveling to loads is vital.

A wide range of current-sensing technologies exist, each one with a long list of pros and cons that must be considered in the context of the overall system and the environmental conditions it is operating in.

But the most common method for measuring current is to put a shunt resistor—also called a current-sense resistor—in the path of the load. Depending on the resistance value, the device outputs a voltage signal that’s proportional to the current traveling through it. Using Ohm's Law, where the relationship of voltage equals current times the resistance (V = I × R), and assuming a stable resistance, the voltage signal can be used—once it’s sufficiently gained and conditioned—to interpret the current.

Shunt-based current sensors are so widespread thanks to their ease-of-use and ability to accurately measure AC and DC currents from milliamps to several hundred amps. While they come with a wide range of form factors and resistance values, shunts can struggle to handle large amounts of power and aren’t galvanically isolated. Thus, they’re not the best fit for every situation. But current transformers and other passive components can fill in for them in many cases.

As power levels continue to rise in everything from electric vehicles (EVs) to solar and other renewable-energy systems to new power-hungry AI processors inside vast data centers, semiconductor companies think they can do better. Allegro Microsystems, ROHM Semiconductor, Texas Instruments, and many others are rolling out current-sensor ICs that they say bring more to the table than traditional passives. In this product roundup, we will review some of the latest offerings to hit the market.

Check out the previous Products of the Week gallery here.

You can also visit the Products of the Week archives here.

About the Author

James Morra | Senior Editor

James Morra is a senior editor for Electronic Design, covering the semiconductor industry and new technology trends, with a focus on power electronics and power management. He also reports on the business behind electrical engineering, including the electronics supply chain. He joined Electronic Design in 2015 and is based in Chicago, Illinois.