Frequency Lock Loop "FLL" technique

I'm working on a new FLL (Frequency Lock Loop) technique. This technique uses Digital Processing thecnique instead of Phase Lock (PLL) technique. I need to biuild a frequency synthesizer to see the perfomance compare with the PLL techniaue. The hardwares required to build this synthesizer are DAC, VCO and two counters. The rest of digital processing can be implemented with either software or hardware. I have chosen a VCO that has a range from 100Mhz~200Mhz. This VCO requires a voltage range from 0v~12.5v. Any recommendation for a 12~14 bit DAC plus an Op Amp (if DAC does not have a 0~12.5v swing) for this application? Thank you.