GENERAL DESCRIPTION

The 874003 is a high performance Differential-to-LVDS Jitter

Attenuator designed for use in PCI Express systems. In some

PCI Express systems, such as those found in desktop PCs, the

PCI Express clocks are generated from a low bandwidth, high

phase 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 874003 has 3 PLL bandwidth

modes: 200kHz, 400kHz, and 800kHz. The 200kHz mode will

provide maximum jitter attenuation, but with higher PLL tracking

skew and spread spectrum modulation from the motherboard

synthesizer may be attenuated. The 400kHz provides an

intermediate bandwidth that can easily track triangular spread

profi les, while providing good jitter attenuation. The 800kHz

bandwidth provides the best tracking skew and will pass most

spread profi les, but the jitter attenuation will not be as good

as the lower bandwidth modes. Because some 2.5Gb serdes

have x20 multipliers while others have than x25 multipliers, the

874003 can be set for 1:1 mode or 5/4 multiplication mode (i.e.

100MHz input/125MHz output) using the FSEL pins.

The 874003 uses IDT’s 3rd Generation FemtoClock®

PLL technology to achive the lowest possible phase noise.

The device is packaged in a 20 Lead TSSOP package, making

it ideal for use in space constrained applications such as PCI

Express add-in cards.

FEATURES

• Three Differential LVDS output pairs

• One Differential clock input

• CLK and nCLK supports the following input types:

LVPECL, LVDS, LVHSTL, SSTL, HCSL

• Output frequency range: 98MHz - 160MHz

• Input frequency range: 98MHz - 128MHz

• VCO range: 490MHz - 640MHz

• Cycle-to-cycle jitter: 35ps (maximum)

• 3.3V operating supply

• Three bandwidth modes allow the system designer to make

jitter attenuation/tracking skew design trade-offs

• 0°C to 70°C ambient operating temperature

• Available in lead-free RoHS compliant package