LMK04832-SP: HyperLynx Sim - Diff IBIS Model Outputs not as Expected

Tool/software:

Hello,

I'm new to HyperLynx and I'm getting unexpected results with a simple IBIS simulation using the lmk04832_sp.ibs model. I want to simulate the CLKout2/CLKout2* pair driving a typical FPGA SERDES REFCLK input. I setup the model as follows:

For CLKout2:

For CLKout2*:

The schematic looks like this:

The resulting waveform shows that the two output pins are very different in amplitude:

CLKout2 measures 295.7 mVpp at pin 15
CLKout2* measures 1.40 Vpp at pin 16

I can select either pin as inverted in the Assign Models Dialog box and the amplitudes at each pin remain unchanged.

I removed the AC coupling capacitors and I get a better result. The schematic looks like this:

The resulting waveform shows that the two output pins are very similar in amplitude:

CLKout2 measures 533.6 mVpp at pin 15
CLKout2* measures 533.6 mVpp at pin 16

This is closer to what I expect.

In trying to get to the bottom of this, I notice that the IBIS model doesn't have the [Diff Pin] section that I've seen in other IBIS models with differential outputs.

Question: Is this a model problem, or is the LMK04832-SP not suitable for driving an AC coupled load?

Thanks,

Rob