Reducing EMI with PhaseLink’s Spread Spectrum Technology Revised Sep. 2001 EMI - Electro-Magnetic Interference • Electromagnetic waves generated by electric signals – Particularly: frequency generators, clock chips... – Depending on source: • different frequency spectrum • different energy level • Interfere with proper functioning of other components • May be harmful to the metabolism EMI reduction with PhaseLink's SST technology author: Li Lei Tsien EMI must be limited by Law • Peak EMI: – Highest energy level at any given frequency – Must be limited by law • limits may vary for different applications • It is the peak emission at any given frequency that must be limited, not the average emissions over the complete frequency spectrum EMI reduction with PhaseLink's SST technology author: Li Lei Tsien Better to reduce the EMI at the source • Two methods to reduce EMI – Enclosing the EMI (traditional): • additional shielding • special coating • filtering equipment – At the source (Spread Spectrum): • choosing the right components • Reducing at the source will generate savings – Game consoles: up to 10$ per unit EMI reduction with PhaseLink's SST technology author: Li Lei Tsien What is SST? (Spread Spectrum Technology) • Modifies electromagnetic wave forms at the source – “Spreads” the frequency spectrum • to lower and higher frequencies – Without increasing the total energy emitted • same average energy level Energy level • Energy level No spread Spread Spectrum Frequency spectrum Frequency spectrum Therefore: reduces peak emissions EMI reduction with PhaseLink's SST technology author: Li Lei Tsien Impact on clock generation • Slight cyclical variation of the output frequency – Frequency (F) goes up and down very slowly • sweep rate (~30-60kHz) – Maximum F not exceeding 4% • typical 0.5% to 1.5% • Center spread: nominal F at center of F variations • average F = nominal F • Down spread: nominal F is also maximum F • avoids over-clocking • average F < nominal F EMI reduction with PhaseLink's SST technology author: Li Lei Tsien More specifically: in the Frequency Domain Spread Spectrum Spread Spectrum EMI reduction at 9th harmonic - Center Spread of +/-0.5% EMI reduction at 9th harmonic - Down Spread of - 1% -10 -10 dB -50 dB > 18 dB reduction -30 > 18 dB reduction -30 -50 -70 -70 -90 -90 -110 -110 F 0 - 0.5% F0 Frequency F 0 + 0.5% F 0 - 1% Fc F0 Frequency EMI reduction with PhaseLink's SST technology author: Li Lei Tsien More Specifically: Measurements from Spectrum Analyzer 18 dB EMI reduction (9th harmonic - center spread +/- 1%) - P L L 7 0 1 -10 EMI reduction with PhaseLink's SST technology author: Li Lei Tsien More Specifically: Modulation Profile in the Time Domain • PhaseLink’s proprietary SST modulation uses a TRIANGULAR modulation profile frequency Fmax F center time Fmin SST Modulation Period (modulation frequency 30-60kHz) EMI reduction with PhaseLink's SST technology author: Li Lei Tsien PhaseLink’s advantages • Proprietary SST • Selectable max. frequency deviation – From 0.25% to 4% • Selectable sweep rate • EMI reduction up to 20dB EMI reduction with PhaseLink's SST technology author: Li Lei Tsien PhaseLink’s Low EMI product families PC Motherboards Cons. Electr. & General Purpose LAN and Networking PLL202-xx FTGs for Intel based chipsets PLL203-xx Intel Solano i815 Chipsets FTGs PLL205-xx FTGs for AMD based chipsets PLL701-xx Multiple output clock multiplier with Low EMI functionality PLL702-xx General purpose FTGs with Low EMI functionality PLL701-xx Multiple output clock multiplier with Low EMI functionality EMI reduction with PhaseLink's SST technology author: Li Lei Tsien