I am unclear on the output polarity of LKDOP on the HMC1031 - I presumed active high indicates the PLL is locked, but now I am uncertain. Can you clarify?
That is correct. When LKDOP is high (3.3V) the part is locked. This part is susceptible to false out-of-lock indications (LKDOP=low but the part is actually locked) due to excessive leakage currents on the charge pump output pin. See the lock detector section on page 10 of the datasheet.
Thank you for the reply. I did some test to confirm this as well. I was confused because on pg. 6 Figure 4 seems to indicate that the output would be low when the "Lock" condition is true..