Achieve Precise High Current Monitoring Using Standard Surface-Mount Resistors

by Viktor Vogman, Power Conversion Consulting, Olympia, Washington, How2Power Today, May 16 2018

Focus:
In low-voltage, high-current applications, designers are required to use very low (sub- milliohm) resistance sensors for current sensing. High-power-rated sub-milliohm sensors often come with Kelvin connect terminals, which simplify layout, but take up PCB space, and are less accurate and more expensive than standard precision surface-mount (SM) parts. When connected in parallel, conventional SM two-terminal parts can support the sub-milliohm resistance range of the sensor. With proper PCB trace routing and summing signals of paralleled sensors a much better (1%) current signal monitoring accuracy can be achieved even without calibration. The specifics of achieving optimal sensing accuracy and paralleled sensor signal routing are discussed in this article. Discussion includes use of equal current path lengths, Kelvin connections, and summing resistors. The impact of the number of sensors paralleled on accuracy is also discussed.

What you’ll learn:

• How to achieve accurate current sensing when paralleling standard surface-mount resistors

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