I am now using 3 wire SPI with the ADF4372 so I can use the Mux out pin to output N/2. However I have discovered that the digital lock detect readback ( as determined by bit 0 of reg 7C) does not work unless the MUX select ( bits 7:4 of reg 20) is set to 0001 .
This is a real nuisance , as it means that I cannot use the Mux out to output N/2 or R/2 without losing the lock detect readback. I want to use the N/2 output to drive an external analog phase detector.
Could you please confirm this, and suggest any register settings that would avoid it.
A further question: The default settings disable the bleed current, however the notes suggest that the bleed should be on. Presumably the bleed current is only appropriate in fractional mode. Should I switch on the bleed in fractional modes, or use the default?
Also, what is the BLEED_GATE function.
Also, should I change the LPD vale ( reg 27) when changing from integer to fractional modes?