Hi Marty,
I'm struggling a bit with the EVAL-HMC767LP6CE around the reference divider 'R' and the lock detect output.
In general, I find setting the R divider to 2 or anything other than 1 the charge pump output rails pushing the VCO to the lowest freq... I have even redesigned the loop filter for the appropriate phase detector comparison frequency. When I try to observe the reference divider output on the LD_SDO pin I only see an output when R=1 but setting it to other than 1 there is no output on the LD_SDO pin. I would like to work in integer mode with an R divider.
Putting that aside, in fractional mode, when I use a 10 MHz reference with R=1 I cannot get the lock detect to assert itself, even though the output looks to be locked. I have adjusted the loop filter accordingly.
As a side note, using the HMC PLL VCO Evaluation Software V3280 and selecting HMC767 fractional default register settings, register 07h looks different than what the Users Guide (140-00074-00 revA PLLs WITH INTEGRATED VCO - MICROWAVE APPLICATIONS PRODUCT & OPERATING GUIDE - COVERS HITTITE PART NUMBER HMC767LP6CE, HMC769LP6CE, HMC778LP6CE) calls for default values. For example [10:3] calls for 12d but the tool programs it to 11d when default values are loaded.
