HMC747 the rising edge

When I was using the HMC747 evaluation board, I found that as long as the D terminal of the HMC747 changes, the Q terminal changes immediately. There is no need to wait for the rising edge of the C terminal. I don't know what is going on?
My DP port is connected to a 1KHZ square wave, the high level is 3.3V, the low level is 2V, and the DN port is suspended.