ADRF6602 - Should the duty cycle of Lock Detect seen on MUXOUT be 50% when locked?
The Lock Detect signa which is the default output on MUXOUT, l is an active-high static signal. If the PLL is not locked (e.g. no reference present), it will stay low. If you are locked, it will idle high. If you switch from one frequency to another, you will see a number of low pulses on Lock Detect before it returns to the high state when the PLL locks to the new frequency.