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Spread-spectrum EMI reducer targets USB 2.0 links

Posted: 03 Apr 2008 ?? ?Print Version ?Bookmark and Share

Keywords:USB 2.0? spread-spectrum approach? EMI suppression?

When faced with EMI problems, you can use various EMI reduction techniques, including carefully sized and placed passives (ferrites, capacitors, inductors) and active, spread-spectrum timing. The passive solution seems like the simpler approach, but it requires board space, usually takes numerous configuration iterations, is very layout (and PCB-revision) dependent, can degrade signal integrity and edge rise/fall time, and is prone to inadvertent defeat as a result of component substitution on the BOM by the assembly house.

PulseCore Semiconductor has introduced what it claims is the first spread-spectrum IC approach to radiated EMI reduction expressly designed for USB 2.0 links. Their PCS3P73UOOA Peak EMI Reduction IC embodies a patent-pending technique that implements a highly granular spread-spectrum algorithm, to meet the extremely tight timing and frequency-domain limits of the USB compliance standard. Rather than manage the system clocks directly, this IC is placed between the 48MHz clock source typically used in USB 2.0 designs and the physical-layer interface IC.

The active-suppression technique reduces radiated EMI by 3dB to 5dB, which is enough in many cases to meet compliance requirements. PulseCore says their active EMI-suppression IC preserves transmission distance, maintains critical clock edges and has no negative impact on signal integrity.

The 8-lead IC is appropriate for motherboards, peripherals, hubs and other USB 2.0 products. It operates from a single 3.2/2.5 V supply, and is available in TSSOP, SOIC and 2mm x 2mm TDFN COL packages.

Pricing is under $1 each, in quantities of at least 3,000 pieces. The device is currently sampling.

- Bill Schweber
Planet Analog

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