I am programming the part with a microcontroller on a new synthesizer PCB and notice that usually the PLL locks up with a significant number of close-in spurs (+/- 22KHz and their harmonics). Occasionally it will lock without those spurs if I keep reprogramming with the identical settings. The output frequency is 6200.0 MHz (integer) using a 10 MHz fosc with the reference doubler. After programming, I clear the FCAL_EN bit, then immediately set it. I'm also not using any calibration assistance. Apparently the PLL locks differently each time.
If you can provide any assistance, it would be greatly appreciated. The spectrum analyzer screen shots are below.
Bad lock:
Good lock:
Regards,
Stan
