Datasheet

8 LMK00304EVM User’s Guide March 2012
9. Clock Outputs
By default, Bank A and Bank B outputs are configured for LVPECL mode, and are source-terminated with
160 ohm resistors and AC coupled to the SMA connectors labeled CLKoutA#+ / CLKoutA#- and 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.
9.1. 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.