I have some questions about the lock detect of HMC984. When I use this chip as a phase detector in a PLL ,
I find that the DTSTO is not show locked in some frequencies, But this frequencies is locked in the Spectrum Analyzer(Agilent UXA).
1： I read the register 0x10,0x11,0x12. I find the frequencies that is unlocked (DTSTO=0,but is locked from Spectrum Analyzer), the 0x12 =00. 0x11=0100002. 0x10=00000054
2： I find the frequencies that is locked(DTSTO=1), that have two conditions (a&b)
- 0x12=04, 0x11=0100004, 0x10=00000058
- 0x12=06, 0x11=0000076, 0x10=000001b1 (all Hexadecimal)
3: My register configurations is 0x03=CCC, 0x06=080007F, 0x07=441000， 0x08=C1
When the PFD is higher than 96MHz or lower than 17MHz, the lock detect will be unlock.
At the same time ,I watch the signal from spectrum analyzer, it is stable in 500Hz span.