What does the CLKOUTx driver look like in LVPECL mode and HSDS mode.
What is the circuit difference between HSDS 6ma and 8ma.
I have a part that need 6ma through 100 ohm but the common mode is at very low level. (.9Vcmos and needs to be DC coupled)
I want to spice my propose circuit and I would like to put the driver in , as close to the real driver as possible.
Hello Kim,
I think you should use LCPECL instead, LCPECL is intended for DC-coupling to very low voltage systems. By increasing Rs with respect to Rb, LCPECL common mode voltage and swing can be reduced for 0.9V systems.
We do not have SPICE models of the LMK04832 output drivers. We do have IBIS models of the LMK04832 circuit, which can help with signal integrity simulations. I strongly recommend using the IBIS models if possible, as these output formats have frequency dependencies that are not going to be well-modeled by any approximation. Varying the values of Rs and Rb to set the common-mode voltage will also be much easier if you can use the IBIS model. Unfortunately, at this time I cannot provide an equation to set Rs or Rb; without using the IBIS model, some experimentation will be required.
If you still need some insight into the internals of the LVPECL/HSDS, please let me know. Any information I can provide will be very limited, and probably will not extend past the datasheet guidelines. Based on what you are trying to do, I think you will not be able to use HSDS as the common mode voltage for this signal is much higher (1.4V to 1.6V). Likewise, you could use LVPECL, but LCPECL is essentially the same driver with lower common-mode voltage.
Regards,
