9©2015 Integrated Device Technology, Inc. Revision C, September 20, 2016
87946I-01 Datasheet
Application Information
Recommendations for Unused Input and Output Pins
Inputs:
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 1k resistor can be used.
Outputs:
LVCMOS Outputs
All unused LVCMOS output can be left floating. There should be no
trace attached.
Wiring the Differential Input to Accept Single Ended Levels
Figure 1 shows how the differential input can be wired to accept
single ended levels. The reference voltage V_REF = V
DD
/2 is
generated by the bias resistors R1, R2 and C1. This bias circuit
should be located as close as possible to the input pin. The ratio of
R1 and R2 might need to be adjusted to position the V_REF in the
center of the input voltage swing. For example, if the input clock
swing is only 2.5V and V
DD
= 3.3V, V_REF should be 1.25V and
R2/R1 = 0.609.
Figure 1. Single-Ended Signal Driving Differential Input
Single Ended Clock Input
V
DD
PCLK
nPCLK
R1
C1
0.1u R2
1K
1K
V_REF
