ADVANCE INFORMATION
CRYSTAL-TO-MLVDS PCI EXPRESS™
ICS845204
CLOCK SYNTHESIZER W/SPREAD SPECTRUM
General Description
Features
The ICS845204 is a 4 output PCI Express clock
• Four differential spread spectrum clock outputs
S
IC
synthesizer optimized to generate low jitter PCI
Express™ reference clocks with or without spread
spectrum modulation and is a member of the
HiPerClockS™ family of high performance clock
• Each output can be individually disabled by separate
HiPerClockS™
output-enable inputs
• Crystal oscillator interface designed for 18pF,
25MHz parallel resonant crystal
solutions from IDT. Spread type and amount can be configured via
the SSC control pins. Using a 25MHz, 18pF parallel resonant
crystal, the device will generate M-LVDS clocks at either 25MHz,
100MHz, 125MHz or 250MHz. The ICS845204 uses a low jitter
VCO that easily meets PCI Express jitter requirements and is
packaged in a 32-pin VFQFN package.
• Supports the following output frequencies:
25MHz, 100MHz, 125MHz or 250MHz
• VCO range: 250MHz - 700MHz
• Supports SSC downspread at 0.05% and -0.75%, centerspread
at 0.25% and no spread options
• Cycle-to-cycle jitter: 50ps (maximum) design target
• Period jitter, RMS: TBD
Pin Assignment
• Full 3.3V output supply mode
• 0°C to 70°C ambient operating temperature
• Available in both standard (RoHS 5) and lead-free (RoHS 6)
packages
32 31 30 29 28 27 26 25
1
2
3
4
5
6
7
8
nc
OE0
24
23
22
21
20
nc
VDD
nQ3
Q3
GND
Q2
VDDO
nQ2
SSC1
nc
nc
FSEL0
nc
19
18
17
GND
9
10 11 12 13 14 15 16
Block Diagram
ICS845204
0 0 PLL Bypass
Q0
32 Lead VFQFN
5mm x 5mm x 0.925mm
package body
25MHz
nQ0
XTAL_IN
Pullup
Phase
Detector
VCO
250-700MHz
OE0
OSC
0 1 ÷5
1 0 ÷4
1 1 ÷2
K Package
Top View
Q1
XTAL_OUT
nQ1
OE1
Pullup
Feedback Divider
Q2
÷20
nQ2
OE2
Pullup
Pullup
2
2
Q3
Pullup:Pullup
Spread Spectrum
Control
SSC[1:0]
nQ3
OE3
Default = 100MHz
Pulldown:Pullup
FSEL[1:0]
The Advance Information presented herein represents a product that is developmental or prototype. The noted characteristics are design targets. Integrated
Device Technologies, Inc. (IDT) reserves the right to change any circuitry or specifications without notice.
IDT™ / ICS™ M-LVDS CLOCK SYNTHESIZER
1
ICS845204AK SEPTEMBER 25, 2007