The ICS874004 is a high performance Differentialto HCSL Jitter Attenuator designed for use in PCI HiPerClockSTM ExpressTM systems. In some PCI ExpressTM systems, such as those found in desktop PCs, the PCI ExpressTM clocks are generated from a low bandwidth, highphase noise PLL frequency synthesizer. In these systems, a jitter attenuator may be required to attenuate high frequency random and deterministic jitter components from the PLL synthesizer and from the system board. The ICS874004 has 3 PLL bandwidth modes: 200KHz, 400KHz, and 800KHz. 200KHz mode will provide maximum jitter attenuation, but with higher PLL tracking skew and spread spectrum modulation from the motherboard synthesizer may be attenuated. 400KHz provides an intermediate bandwidth that can easily track triangular spread profiles, while providing good jitter attenuation. 800KHz bandwidth provides the best tracking skew and will pass most spread profiles, but the jitter attenuation will not be as good as the lower bandwidth modes. Because some 2.5 Gb serdes have x20 multipliers while others have than x25 multipliers, the 874004 can be set for 1:1 mode or 5/4 multiplication mode (i.e. 100MHz input/125MHz output) using the F_SEL pin.