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ADF4001 Analog Lock Detect

Question asked by Mark_B on Jan 18, 2016
Latest reply on Jan 19, 2016 by Brigid.Duggan

I am using the ADF4001 to lock a 40 MHz VCXO to a 10 MHz reference (Vdd = 3.3 V). The PLL locks and the digital lock detect from the MUXOUT goes high. When I switch to the analog lock detect with a pullup of 10k, the lock detect signal is not a high with narrow low-going pulses as described in the datasheet. The signal is a sawtooth waveform that goes from 0.8 V to 1.0 V (the pullup resistor is going to a 2.5 V supply). Every other signal that comes from the MUXOUT looks correct (R-divider output, N-divider output). What is going on the the analog lock detect? Why is it not a high signal with narrow low-going pulses?