DIFFERENTIAL-TO-LVDS/0.7V DIFFERENTIAL

PCI EXPRESS™ JITTER ATTENUATOR

ICS8741004

IDT™ / ICS™ PCI EXPRESS™ JITTER ATTENUATOR

1

ICS8741004AG REV. AAUGUST 3, 2007

General Description

The ICS8741004 is a high performance

Differential-to-LVDS/0.7V Differential 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 ICS8741004 has 3 PLL bandwidth modes: 200kHz,

600kHz and 2MHz. 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 600kHz provides an intermediate bandwidth that

can easily track triangular spread profiles, while providing good

jitter attenuation. The 2MHz 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

2.5Gb serdes have x20 multipliers while others have x25

multipliers, the ICS8741004 can be set for 1:1 mode or 5/4

multiplication mode (i.e. 100MHz input/125MHz output) using the

F_SEL pins.

PLL technology to achieve the lowest possible phase noise.

The device is packaged in a 24 Lead TSSOP package, making it

ideal for use in space constrained applications such as PCI

Express add-in cards.

PLL Bandwidth

Features

Bank A has two LVDS output pairs and

Bank B has two 0.7V differential output pairs

input levels: LVPECL, LVDS, LVHSTL, SSTL, HCSL

jitter attenuation/tracking skew design trade-offs

packages

Pin Assignment

ICS8741004

24-Lead TSSOP

4.4mm x 7.8mm x 0.925mm

package body

G Package

Top View

BW_SEL

0 = PLL Bandwidth: ~200kHz

Float = PLL Bandwidth: ~600kHz (default)

1 = PLL Bandwidth: ~2MHz

HiPerClockS™

ICS

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

QA1

QA1

QA0

QA0

MR

BW_SEL

nc

F_SELA

OEA

QB1

QB1

QB0

QB0

IREF

F_SELB

OEB

GND

GND

CLK

CLK