ICS859S0424I Datasheet, PDF (18/24 Pages) Integrated Device Technology – Four programmable differential LVPECL or LVDS output pairs

ICS859S0424I Data Sheet
4:4 DIFFERENTIAL-TO-LVPECL/LVDS CLOCK MULTIPLEXER
LVDS Driver Termination
For a general LVDS interface, the recommended value for the
termination impedance (Z_T) is between 90Ω and 132Ω. The actual
value should be selected to match the differential impedance (Z₀) of
your transmission line. A typical point-to-point LVDS design uses a
100Ω parallel resistor at the receiver and a 100Ω differential
transmission-line environment. In order to avoid any
transmission-line reflection issues, the components should be
surface mounted and must be placed as close to the receiver as
possible. IDT offers a full line of LVDS compliant devices with two
types of output structures: current source and voltage source. The
standard termination schematic as shown in Figure 6A can be used
with either type of output structure. Figure 6B, which can also be
used with both output types, is an optional termination with center tap
capacitance to help filter common mode noise. The capacitor value
should be approximately 50pF. If using a non-standard termination, it
is recommended to contact IDT and confirm if the output structure is
current source or voltage source type. In addition, since these
outputs are LVDS compatible, the input receiver’s amplitude and
common-mode input range should be verified for compatibility with
the output.
LVDS
Driver
Z_O • Z_T
Figure 6A. Standard Termination
LVDS
Z_T
Receiver
LVDS
Driver
Z_O • Z_T
Figure 6B. Optional Termination
LVDS Termination
Z_T
2 _LVDS
C
Z_T Receiver
2
ICS859S0424BGI REVISION A OCTOBER 12, 2011
18
©2011 Integrated Device Technology, Inc.