Hello,
We need to be able to reliably detect presence of a 13kHz rectangular signal in the input, so we decided to try LMC567 part for that. It works but the detector triggers also for near frequencies, we get at least occasional 0 output (meaning the PLL is locked) for the frequence range from 12.1kHz to 13.9kHz.
What we need is to lower this detection width to 1kHz, i.e. to detect signals from 12.5kHz to 13.5kHz. We tried using different capacitance on the PLL feedback pin (pin 2) but the band didn't get any significantly narrower, only the intervals where the IC output is oscillating got wider.
This oscillogram measured on central frequency (13.0 kHz).
We would be grateful for any suggestions, thank you in advance.
