HMC6832 rise time 170ps LVPECL

Hi,

we are using the HMC6832 in a new design and need the fast rise time to be around 50ps but we are surprised to find out that it is around 170ps (20/80) instead. Not sure what is going on. The amplitude at the output single ended is around 330mVpp. The signal at the input is differential with around 1000 mVppd. The buffer is configured to output LVPECL and has 150Ohm resistors on the output. the output signal is going to an SMPM connector and from there with a coax to the scope (86108A with 32GHz BW) where we are measuring 170ps risetime.

On the same board, there is another buffer LTC69555 with a fast rise time of about 50ps and this one is working fine.

The HMC6832 circuit is as below. Any hints?

Thanks,

Ralph