3.5.2 Differential Output Terminations
LVDS Driver Termination
For a general LVDS interface, the recommended value for the differential termination impedance (Z
T
) is between 90 Ω and 132
Ω. The actual value should be selected to match the differential impedance (Z0) of the transmission line. A typical point-to-point
LVDS design uses a 100 Ω parallel resistor at the receiver and a 100 Ω 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. The standard LVDS termination schematic as shown in
Figure 3.5 Standard LVDS Termination on page 12
can be used with
either type of output structure.
Figure 3.6 Optional LVDS Termination on page 12
, 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
0.01 to 0.1 μF. If using a non-standard termination, please contact Skyworks to 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.
Si5332
LVDS Output
Driver
Zo = Z
T
/2
+
-
LVDS
Receiver
Z
T
Zo = Z
T
/2
Figure 3.5. Standard LVDS Termination
+
-
LVDS
Receiver
Z
T
/2
Z
T
/2
C
Zo = Z
T
/2
Zo = Z
T
/2
Si5332
LVDS Output
Driver
Figure 3.6. Optional LVDS Termination
Termination for 3.3 V LVPECL Outputs
The clock layout topology shown below is a typical termination for LVPECL outputs. The two different layouts mentioned are recom-
mended only as guidelines. The differential outputs generate ECL/LVPECL compatible outputs. Therefore, terminating resistors (DC
current path to ground) or current sources must be used for functionality. These outputs are designed to drive 50 Ω transmission
lines. Matched impedance techniques should be used to maximize operating frequency and minimize signal distortion.
LVPECL Output Termination, Option 1 on page 13
Figure 3.8 3.3 V LVPECL Output Termination, Option 2 on page 13
different layouts. Other suitable clock layouts may exist, and it would be recommended that the board designers simulate to guarantee
compatibility across all printed circuit and clock component process variations.
Si5332 Data Sheet • Functional Description
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • November 16, 2021
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