Abstract

For low-noise medical imaging applications, reducing the effects of electromagnetic interference (EMI) becomes an increasingly critical system design consideration. Designing for low EMI can save you significant development cycle time while also reducing board area and design cost. Though component selection makes huge difference in reducing EMI, optimized layout plays a significant role in reducing EMI as well.

This application note discusses the improvements in conducted and radiated emissions of four latest buck devices from TI. Using the example of two buck converters (TPS543820 and TPS543A22) and two buck converter modules (TPSM843620 and TPSM843A22), the effects of PCB layout and input filtering are observed. Note that these converters and modules are related: the TPSM843A22 is the module version of the TPS543A22 converter, and the TPSM843620 is the 6A module version of the TPS543820 converter.

New EMI-friendly layouts are designed to test the effects of improved layout on EMI performance. Consequently, the boards were all tested with and without a 2nd order input pi filter to test the effects on EMI performance. In the redesigned PCBs optimized for EMI performance, layout techniques such as via stitching, minimized high di/dt current loops, and improved power density were used to minimize noise.

By the end of this article, the reader can have an idea of the extent to which PCB layout and proper input filtering can affect EMI performance of buck converter designs.