I used HMC704's integrated mode in my project. I changed the output frequency from 7500MHz to 7000MHz. I tested the SCLK pin, SEN pin and VTrun of VCO using oscilloscope and found there is a delay about 50uS between finished writing registers and charge pump outputting(the delay is shown in blow picture). now my question is why there is delay? Dose HMC704 indeed has that delay or I made a mistake in wiriting registers? I tested HMC704 in fractional mode, there is not delay.
Program Reg0Ah = 1800h. If it is left at its default value (2005h), the VCO Auto-calibration feature is enabled and will be triggered every time a frequency is programmed. This feature is only used on HMC PLLVCO products that use the same PLL die as the HMC704. This feature serves no useful function in the HMC704 and it should be disabled (by programming Reg0Ah = 1800h).