
ICS844251-14
FEMTOCLOCK CRYSTAL-TO-LVDS CLOCK GENERATOR
IDT / ICS LVDS CLOCK GENERATOR
10
ICS844251BG-14 REV. A NOVEMBER 19, 2012
Schematic Example
Figure 5 shows an example of ICS844251-14 application
schematic. In this example, the device is operated at VDD = 3.3V.
The decoupling capacitor should be located as close as possible
to the power pin. The 18pF parallel resonant 25MHz crystal is
used. The C1 = 27pF and C2 = 27pF are recommended for
frequency accuracy. For different board layouts, the C1 and C2
may be slightly adjusted for optimizing frequency accuracy. For the
LVDS output drivers, place a 100
resistor as close to the receiver
as possible.
Figure 5. ICS844251-14 Schematic Example
C2
27pF
RD1
Not Install
U1
1
2
3
4
8
7
6
5
VDDA
GND
XTAL_OUT
XTAL_IN
VDD
Q
nQ
FREQ_SEL
R4
50
C3
0.1u
Zo = 50 Ohm
To Logic
Input
pins
FREQ_SEL
VDDA
C7
0.1uF
C1
27pF
RU1
1K
Set Logic
Input to
'0'
VDD
Alternate
LVDS
Termination
R3
50
VDD
Zo = 50 Ohm
VDD
+
-
Set Logic
Input to
'1'
VDD
+
-
Q
Zo = 50 Ohm
nQ
C4
10u
C5
0.01u
Logic Input Pin Examples
X1
25 MHz
nQ
RD2
1K
1 8 p F
RU2
Not Install
To Logic
Input
pins
R1
10
Q
R2
100