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©2015 Integrated Device Technology, Inc.

Revision C, December 8, 2015

8545 Datasheet

Applications Information

Recommendations for Unused Input and Output Pins

Inputs:

CLK Inputs

For applications not requiring the use of a clock input, it can be left

floating. Though not required, but for additional protection, a 1k



resistor can be tied from the CLK input 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 1k

 resistor can be used.

Outputs:

LVDS Outputs

All unused LVDS output pairs can be either left floating or terminated

with 100

 across. If they are left floating, there should be no trace

attached.

LVDS Driver Termination

For a general LVDS interface, the recommended value for the

termination impedance (ZT) is between 90 and 132. 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

100

 parallel resistor at the receiver and a 100 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 2 can be used

with either type of output structure. Figure 3, 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.

Figure 2. Standard LVDS Termination

Figure 3. Optional LVDS Termination

LVDS

Driver

ZO  ZT

ZT

LVDS

Receiver

LVDS

Driver

ZO  ZT

LVDS

Receiver

C

ZT

2

ZT

2