How is the VCO frequency determined in the MAX2223?

When using the MAX2223, note that the VCO frequency is not the same as the LO frequency. For LO frequencies below 1125 MHz, the VCO runs at 4×LO due to a divide-by-4 output. For example, at 950 MHz LO, the VCO is at 3800 MHz. At 925 MHz LO, it’s 3700 MHz; at 1124 MHz, it’s 4496 MHz. At 1125 MHz and above, the divide-by-2 is used, so the VCO is 2250 MHz at 1125 MHz LO and 4350 MHz at 2175 MHz LO. This gives a VCO tuning range of 2250–4496 MHz. Some margin should be assumed at both ends, and overlapping bands likely ensure smooth transitions.

MAX2120/2112/2120 Fast Lock Time Ap Note. Does this application note also apply to MAX2223, and what are the VCO band frequencies?

The application note for faster lock time configuration( https://www.analog.com/en/resources/design-notes/tuner-configuration-for-faster-lock-time.html) also applies to the MAX2223. Use the VCO band frequencies from the MAX2121 as specified in the application note. The MAX2223 is essentially the MAX2121 without the baseband filter, and the MAX2121 is derived from the MAX2112. Therefore, the techniques described in the application note are applicable to both the MAX2223 and MAX2121.