ICS556-03 Datasheet, PDF (3/8 Pages) Integrated Circuit Systems – QUAD LVDS OSCILLATOR/BUFFER

ICS556-03
Quad LVDS Oscillator/Buffer
Pin
Number
14
15
16
Pin
Name
D
EN3
Pin
Type
Output
Input
Pin Description
Differential clock output.
Enable pin for Outputs C and C. EN4 high enables C, C outputs.
EN3 low tri states C, C outputs.No Pull-Up resistor.
EN4
Input Enable pin for Outputs D and D. EN4 high enables D, D outputs.
EN4 low tri states D, D outputs.No Pull-Up resistor.
External Component Selection
The ICS556-03 requires a minimum number of external
components for proper operation.
Decoupling Capacitors
A decoupling capacitor of 0.01µF should be connected
between VDD and GND on pins 2 and 10 as close to
the ICS556-03 possible. For optimum device
performance, the decoupling capacitor should be
mounted on the component side of the PCB. Avoid the
use of vias in the decoupling circuit.
LVDS Driver Termination
A general LVDS interface is shown in Figure 2. In a 100
ohm differential transmission line environment, LVDS
drivers require a matched load termination of 100
across near the receiver input. For a multiple LVDS
outputs buffer, if only partial outputs are used, it is
recommended to terminate the un-used outputs.
Quartz Crystal
The ICS556-03, a quad 25 MHz LVDS Clock utilizes an
external crystal to generate 4 pairs of low phase noise
outputs. The crystal should be a fundamental mode,
parallel resonant. Crystal capacitors should be
connected from pins X1 to ground and X2 to ground to
optimize the initial accuracy. The value of these
capacitors is given by the following equation
Crystal Caps (pf)= (C_L-12)x2
In the equation, CL is the crystal Load capacitance. So
for the crystal with 16pF load capacitance, two 8
pF[(16-12)x2] capacitors should be used.
The external crystal must be connected as close to the
chip as possible and should be on the same side of the
PCB as the ICS556-03. There should be no via’s
between the crystal pins and the X1 and X2 device
pins. There should be no signal traces underneath or
close to the crystal.
2.5V
LVDS_Driver
R1
100 ohm
2.5V
+
-
100 Ohm Differential Transmission Line
Figure 2. Typical LVDS Driver
Termination
MDS 556-03 B
3
Revision 030204
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