Designing With a Current Sense Resistor

The current sense resistor is an electronic component that converts the current in a circuit to a voltage that can be easily measured and monitored. Resistors for this purpose are available in a wide range of values and power ratings, from very low milliohms up to kilowatts.

These products are a vital tool for designers of high-current applications, from motors to electric vehicles and RF circuits. They are designed to be easy to use and allow a measuring device to place directly across the sensing terminals to get accurate readings without any disruption of the circuit.

There are a number of issues to consider when designing with a current sense resistor. These include the value, temperature coefficient, power rating and the layout of the circuit around the current sense resistor.

To begin with, the value of the current sense resistor must be carefully selected. This will have a big impact on the accuracy of the readings that can be taken from the circuit. In general, resistors with a low value will have lower heat dissipation and therefore reduce the potential for noise to interfere with the signal.

The power rating of the SEM Sensor should also be considered as it can have a major impact on the overall design, especially when high currents are present. This is a critical factor for motor applications, where the start and run currents can be very different, so it needs to be capable of handling these levels.

Using a current sense resistor involves careful design, as the resistance of the solder pad and copper tracks must be very precise to prevent inaccuracies in the current measurement. The track layout around the component must be carefully designed to ensure that there is no shared conductive path from the PCB tracks to the sensed current path (figure 1).

This is often a very difficult task and can require many iterations before a solution is achieved. This can be especially true of two-terminal resistors that implement the 4-wire Kelvin principle, as they employ additional leads for measuring current more accurately than a standard 2-pad component (figure 2).

Even though these components are relatively inexpensive, their performance can be highly sensitive to a wide range of factors including ohmic values, power losses, TCR, and even the way the resistor is mounted on the PCB. These issues can lead to problems with power integrity, SNR, and other aspects of the circuit.

Despite these challenges, the current sense resistor remains a popular choice for a variety of electronics and electrical designs. Because they can be used in so many applications, they are an excellent example of the trade-offs that must be made to ensure that an electronic circuit performs properly and over a broad range of expected operating conditions. Check out this post for more details related to this article: https://simple.wikipedia.org/wiki/Resistor.