DC/DC controllers with integrated active EMI filter

April 07, 2021 // By Jean-Pierre Joosting
DC/DC controllers with integrated active EMI filter
Latest buck controllers enable designers to optimize the size and EMI of the power supply in industrial and automotive electronics

Texas Instruments has introduced a new family of synchronous DC/DC buck controllers that enable engineers to shrink the size of the power-supply and lower its electromagnetic interference (EMI). Featuring an integrated active EMI filter (AEF) and dual-random spread-spectrum (DRSS) technology, the LM25149-Q1 and LM25149 enable engineers to cut the area of the external EMI filter in half, lower the conducted EMI of the power design by as much as 55 dBµV across multiple frequency bands, or achieve a combination of reduced filter size and low EMI.

Reducing EMI in the power supply is a growing design challenge, especially as electronic content increases in advanced driver assistance systems (ADAS), automotive infotainment and cluster, building automation, and aerospace and defense designs. A traditional way to ensure that a design meets conducted EMI specifications involves increasing the size of the external passive EMI filter, which in turn increases the overall power supply size. By integrating the AEF, the LM25149-Q1 and LM25149 buck controllers enable engineers to meet EMI standards while increasing their design's power density.

The most stringent industry requirements for low-EMI designs are Comité International Spécial des Perturbations Radioélectriques (CISPR) 25 Class 5 automotive EMI specifications. The LM25149-Q1 and LM25149 buck controllers help engineers meet those requirements by mitigating conducted EMI across multiple frequency bands. The integrated AEF helps detect and reduce conducted EMI in the low-frequency band of 150 kHz to 10 MHz, enabling engineers to attenuate EMI by up to 50 dBµV at a switching frequency of 440 kHz, relative to a design with the AEF disabled, or as much as 20 dBµV when compared to a design with a typical passive filter. In both design scenarios, the DRSS technology helps mitigate EMI by an additional 5 dBµV across low- and high-frequency bands.

To further reduce EMI, both buck controllers feature frequency synchronization to an external clock, helping engineers mitigate undesired beat frequencies in applications sensitive to EMI.

Maintaining low


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