ICS859S0424I Datasheet, PDF (16/24 Pages) Integrated Device Technology – Four programmable differential LVPECL or LVDS output pairs

ICS859S0424I Data Sheet
4:4 DIFFERENTIAL-TO-LVPECL/LVDS CLOCK MULTIPLEXER
Recommendations for Unused Input and Output Pins
Inputs:
PCLK/nPCLK Inputs
For applications not requiring the use of a differential input, both the
PCLK and nPCLK pins can be left floating. Though not required, but
for additional protection, a 1kΩ resistor can be tied from PCLK to
ground.
LVCMOS Control Pins
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional protection.
A 1kΩ resistor can be used.
Outputs:
LVPECL Outputs
All unused LVPECL outputs can be left floating. We recommend that
there is no trace attached. Both sides of the differential output pair
should either be left floating or terminated.
LVDS Outputs
All unused LVDS output pairs can be either left floating or terminated
with 100Ω across. If they are left floating, there should be no trace
attached.
Termination for 2.5V LVPECL Outputs
Figure 4A and Figure 4B show examples of termination for 2.5V
LVPECL driver. These terminations are equivalent to terminating
50Ω to V_CC – 2V. For V_CC = 2.5V, the V_CC – 2V is very close to ground
level. The R3 in Figure 4B can be eliminated and the termination is
shown in Figure 4C.
V_CC = 2.5V
50Ω
50Ω
2.5V LVPECL Driver
2.5V
R1
250Ω
R3
250Ω
2.5V
+
–
R2
62.5Ω
R4
62.5Ω
VCC = 2.5V
50Ω
50Ω
2.5V LVPECL Driver
2.5V
+
–
R1
R2
50Ω
50Ω
R3
18Ω
Figure 4A. 2.5V LVPECL Driver Termination Example
Figure 4B. 2.5V LVPECL Driver Termination Example
VCC = 2.5V
50Ω
50Ω
2.5V LVPECL Driver
2.5V
+
–
R1
R2
50Ω
50Ω
Figure 4C. 2.5V LVPECL Driver Termination Example
ICS859S0424BGI REVISION A OCTOBER 12, 2011
16
©2011 Integrated Device Technology, Inc.