SNAS605AS March 2013 – May 2020 LMK04821 , LMK04826 , LMK04828
PRODUCTION DATA.
Figure 30 shows the recommended resistor biasing configuration for the LVDS/HSDS format for both CLKout and OSCout pins. When connecting an HSDS output to a load, it should be AC-coupled. In cases where the common mode output voltage of the LMK0482x family LVDS matches the common mode input voltage of the LVDS receiver, DC coupling can be used; however, frequently LVDS is also AC-coupled to avoid any driver/receiver mismatch issues.
The LVDS/HSDS driver requires a DC path for current from CLKoutX to CLKoutX* and from OSCout to OSCout* on initial startup. If a DC path for current is not present on startup, LVDS/HSDS outputs may start up with lower amplitude than expected, and in some cases could generate runt pulses or fail to oscillate for some time after startup. Whenever AC-coupled LVDS or HSDS is used with external termination, the 100-Ω termination should be placed on the LMK0482x side of the AC-coupling capacitors as illustrated in Figure 30.
In cases where the termination is internal to the receiver, place 560 Ω close to the CLKoutX/X* or OSCout/OSCout* pins, to provide a DC path for the output on startup as illustrated in Figure 31.