
FEMTOCLOCKS– CRYSTAL-TO-
LVDS FREQUENCY SYNTHESIZER
ICS844002-01
IDT / ICS LVDS FREQUENCY SYNTHESIZER
1
ICS844002AG-01 REV. A SEPTEMBER 28, 2007
Description
The ICS844002-01 is a 2 output LVDS Synthesizer
optimized to generate Ethernet reference clock
frequencies and is a member of the HiPerClocksTM
family of high performance clock solutions from IDT.
Using a 25MHz, 18pF parallel resonant crystal, the
following frequencies can be generated based on the 2 frequency
select pins (F_SEL[1:0]): 156.25MHz, 125MHz and 62.5MHz. The
ICS844002-01 uses IDT’s 3rd generation low phase noise VCO
technology and can achieve <1ps typical rms phase jitter, easily
meeting Ethernet jitter requirements. The ICS844002-01 is
packaged in a small 20-pin TSSOP package.
Block Diagram
Features
Two differential LVDS outputs
Selectable crystal oscillator interface or
single-ended LVCMOS/LVTTL input
Supports the following output frequencies: 156.25MHz,
125MHz, 62.5MHz
VCO range: 560MHz – 680MHz
RMS phase jitter @ 156.25MHz, using a 25MHz crystal
(1.875MHz – 20MHz): 0.41ps (typical)
Full 3.3V and 2.5V supply modes
0°C to 70°C ambient operating temperature
Available in both standard (RoHS 5) and lead-free (RoHS 6)
packages
HiPerClockS
ICS
1
0
1
0
Phase
Detector
VCO
625MHz
(w/25MHz
Reference)
M = 25 (fixed)
F_SEL[1:0]
0 0
÷4
0 1
÷5
1 0
÷10
1 1
not used
2
OSC
F_SEL[1:0]
PLL_SEL
XTAL_SEL
MR
REF_CLK
XTAL_IN
XTAL_OUT
Q0
Q1
Pulldown
25MHz
ICS844002-01
20-Lead TSSOP
6.5mm x 4.4mm x 0.925mm
package body
G Package
Top View
Pin Assignment
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
F_SEL0
VDDA
nc
PLL_SEL
MR
Q0
VDDO
nc
VDD
VDDO
Q1
GND
nc
XTAL_SEL
REF_CLK
XTAL_IN
XTAL_OUT
F_SEL1