New Industry Products

Littelfuse Offers Current Sensing Resistors for Automotive and Consumer Applications

July 30, 2023 by Jake Hertz

This article will examine current sensing resistors, potential applications, and the new release from Littelfuse, which the company hopes will enable overcurrent protection and current monitoring in critical electronics. 

One of the most ubiquitous and powerful components in all electronics is the current sense resistor. A simple, low-resistance device meant to provide a straightforward means of detecting current in a system, current sense resistors have found applications in many verticals. 


Circuit board components with lines representing the flow of electrical signals

Circuit board components with lines representing the flow of electrical signals. Image used courtesy of Adobe Stock


Littelfuse recently released new sense resistors particularly optimized for automotive and consumer applications. 


What Are Current Sensing Resistors?

Current-sensing resistors, or shunt resistors, are specific resistor types designed to gauge the quantity of current passing through an electrical circuit. They’ve become a fundamental element in numerous electronic devices, offering a straightforward, immediate, and highly precise technique for current measurement.

The operation of a current-sensing resistor is based on Ohm's Law, which asserts that the current flowing between two points in a conductor is directly proportional to the voltage across these points. When it comes to a current-sensing resistor, the voltage drop across the resistor is recorded, and the current is determined by dividing this voltage by the resistance (I=V/R).


Current sense resistors leverage Ohm’s Law to determine current

Current sense resistors leverage Ohm’s Law to determine current. EE Power image


In practice, this measurement is usually made by connecting one or both terminals of the sense resistor to an amplifier, the output of which goes to a microcontroller’s ADC pin. After converting the analog voltage value to the digital domain and knowing the resistance of the sense resistor, the microcontroller can calculate the current.

To this end, current-sensing resistors typically have a very low resistance value of less than an ohm. With a low resistance, these devices can minimize their impact on the rest of the system during measurement.


Consumer and Automotive Applications

Such simple and effective components, current sensing and current sense resistors have applications in many fields.

In automotive, these components are essential for vehicle operation and safety of EVs. Current sensing can be used to track the power flowing from the battery to the electric motor, for example. This data is crucial for managing the battery's charge and discharge process, controlling the motor's speed, and ensuring the vehicle's overall efficiency and safety.


Current-sensing amplifiers in an EV charger

Current-sensing amplifiers in an EV charger. Image used courtesy of Texas Instruments


Current sensing resistors can also be used in other automotive electronics, such as infotainment systems, advanced driver-assistance systems (ADAS), and lighting systems. They monitor and regulate the current flow, helping to prevent potential damage from overcurrent situations.

The same goes for consumer electronics, where current-sensing resistors can be found in everything from household appliances to personal electronics. Here, current sensing can monitor the battery charging process, regulate the power supplied to various components, and ensure optimal performance and battery longevity.


Littelfuse’s New Offerings

Recently, Littelfuse announced the launch of a family of current sense resistors.

The family has eight new resistor options in different packages made from metal foil, metal strips, and metal plates. Common among all the options is that the devices are designed specifically for measuring circuit currents thanks to a low resistance rating and high manufacturing precision.

Littelfuse automotive-qualified current sense resistors

Littelfuse automotive-qualified current sense resistors. Image used courtesy of Littelfuse


Within this, the company states that the new products are ideal for sectors like automotive and consumer electronics, where monitoring currents is necessary for power management, battery charging, and motor control. Currently, the devices are being sold in quantities of 5000.