Datasheet

8 LMK00306EVM User’s Guide March 2012
8. Clock Outputs
By default, Bank A outputs are configured for LVPECL mode, source-terminated with 160 ohm resistors, and
AC coupled to the SMA connectors labeled CLKoutA#+ / CLKoutA#-. Bank B outputs are configured for
LVDS and AC coupled to SMA connectors labeled CLKoutB#+ / CLKoutB#-. To modify the output interface
for a different output mode, refer to the modifications noted in the Schematics section.
REFout is a LVCMOS output and is AC coupled to its SMA connector.
As noted before, active output traces should be properly terminated; otherwise any unused output pin can be
disconnected from the output trace by removing the 0-ohm series resistor.
8.1. LVPECL and LVCMOS with 2.5 V Vcco
The LVPECL and LVCMOS output levels depend on the output driver’s respective Vcco supply as specified
in the datasheet.
When an output bank is configured for LVPECL and its Vcco supply is 2.5 V, it is suggested to replace the
160-ohm -termination resistor to ground with a lower value, such as 91 ohms, to maintain proper DC
bias current on each output.