how to design ring osc testing buffer ?

Dear all:
Now I design differential Ring OSC 170Mhz,
but I don't know how to design buffer to pad .
I try to use Inverter for testing buffer , but when add package model
it will ringing , so somebody can help me ?

Thanks .

This is probably the capacitive load of the pad that is causing this. Use a bigger inverter or buffer for this purpose. In practice this will result in a trade-in of current consumption against load drive abilities.