I would like to use integermode with HMC832.

I would like to change the frequency that uses VCO Autocalibration.

When Autocalibration is used, the VCO output frequency doesn't settle occasionally.

The setting of the register of VCO when not settling was confirmed.

In that case, VCO SUB-BAND SELECT is not appropriate.Near SUB-BAND had been selected.

Therefore, VCO cannot oscillate in my set frequency.

Therefore, it is thought that the VCO output frequency is not settled.

The probability of the problem decreases when the tcal time is lengthened.

The probability is about 1ppm for n=7 and tcal=20.16uS.

I think that this is issue in the fEER frequency.

Is there a thing that VCO doesn't settle because of the frequency error of tEER?

Is this problem happen as long as VCO Autocalibration is used?

Please disregard the power supply noise and the temperature changes in this case.

Thank you.

We recommend autocal runs for enough time such that Ferror on the final selection is less than 800KHz. The relationship between Ferror and Autocal time (Tcal) is given by Eq 8 on Page 18 in the datasheet. I've attached a spreadsheet you can use to get the calibration time and Ferror for a given reference frequency and Reg 0x0A configuration.

What is your reference frequency and Register 0x0A setting? With 50MHz reference and recommended Register 0x0A setting of 0x2046 (n=7) I get Tcal=36us and Ferror=195KHz.