ADN2855

Data Sheet

Rev. B | Page 16 of 20

Transmission Lines

Use of 50 Ω transmission lines is required for all high frequency

input and output signals to minimize reflections: PIN, NIN,

CLKOUTP, CLKOUTN, DATxP, DATxN (also REFCLKP and

REFCLKN if a high frequency reference clock is used, such as

155.52 MHz). It is also necessary for the PIN/NIN input traces

to be matched in length, and the CLKOUTP/CLKOUTN and

DATxP/DATxN output traces to be matched in length to avoid

skew between the differential traces. All high speed LVDS outputs,

CLKOUTP/CLKOUTN and DATxP/DATxN, require a 100 Ω

differential termination at the differential input to the device

being driven by the ADN2855 outputs.

The high speed inputs, PIN and NIN, are internally terminated

with 50 Ω to an internal reference voltage.

As with any high speed mixed-signal design, take care to keep

all high speed digital traces away from sensitive analog nodes.

Soldering Guidelines for Chip Scale Package

The lands on the 32-lead LFCSP are rectangular. The PCB pad

for these should be 0.1 mm longer than the package land length

and 0.05 mm wider than the package land width. The land

should be centered on the pad to ensure that the solder joint

size is maximized. The bottom of the chip scale package has a

central exposed pad. The pad on the PCB should be at least as

large as this exposed pad. The user must connect the exposed

pad to VEE (GND) using plugged vias so that solder does not

leak through the vias during reflow. This ensures a solid

connection from the exposed pad to VEE.