
FEMTOCLOCKS CRYSTAL-TO-LVDS
CLOCK GENERATOR
ICS844001
IDT / ICS FEMTOCLOCKS CLOCK GENERATOR
1
ICS844001 REV A NOVEMBER 2, 2012
GENERAL DESCRIPTION
The ICS844001 is a Fibre Channel Clock Generator. The
ICS844001 uses an 18pF parallel resonant crystal over the
range of 20.4MHz - 28.3MHz. For Fibre Channel applications, a
26.5625MHz crystal is used. The frequency select pin allows
the device to generate either 106.25MHz or 212.5MHz from a
26.5625MHz crystal. To generate 187.5MHz for 12Gb Ethernet,
a 23.4375MHz crystal is used. The ICS844001 uses IDT’s
3rd generation low phase noise VCO technology and can achieve
<1ps typical rms phase jitter, easily meeting Fibre Channel and
Ethernet jitter requirements. The ICS844001 is packaged in a
small 8-pin TSSOP, making it ideal for use in systems with limited
board space.
NOTE: It is not recommended to overdrive the crystal input with
an external clock.
FEATURES
One Differential LVDS output
Crystal oscillator interface, 18pF parallel resonant crystal
(20.4MHz - 28.3MHz)
Output frequency range: 81.66MHz - 226.66MHz
VCO range: 490MHz - 680MHz
RMS phase jitter @ 106.25MHz, using a 26.5625MHz crystal
(637kHz - 10MHz): 0.74ps (typical)
3.3V or 2.5V operating supply
0°C to 70°C ambient operating temperature
Available in both standard (RoHS 5) and lead-free (RoHS 6)
packages
VDDA
GND
XTAL_OUT
XTAL_IN
1
2
3
4
VDD
Q
nQ
FREQ_SEL
8
7
6
5
BLOCK DIAGRAM
OSC
Phase
Detector
VCO
490MHz - 680MHz
M = ÷24 (fixed)
÷3
÷6
0
1
XTAL_IN
XTAL_OUT
Q
nQ
COMMON CONFIGURATION TABLE - FIBRE CHANNEL, 12Gb ETHERNET
PIN ASSIGNMENT
FREQ_SEL Pullup
s
t
u
p
n
I
y
c
n
e
u
q
e
r
F
t
u
p
t
u
O
)
z
H
M
(
)
z
H
M
(
y
c
n
e
u
q
e
r
F
l
a
t
s
y
r
CL
E
S
_
Q
E
R
FM
N
n
o
i
t
a
c
i
l
p
i
t
l
u
M
N
/
M
e
u
l
a
V
5
2
6
5
.
6
21
4
26
4
5
2
.
6
0
1
5
2
6
5
.
6
20
4
23
8
5
.
2
1
2
5
7
3
4
.
3
20
4
23
8
5
.
7
8
1
ICS844001
8-Lead TSSOP
4.40mm x 3.0mm x 0.925mm
package body
G Package
Top View