I have a receiving circuit built for 262KHz. Antenna, filters and amplifier stages all work great, however my PLL center frequency can drift by as much as ~4KHz. The frequency is drifting due to temperature variations. I can blow on the circuit and it moves +/- 900Hz.
I use a PLL chip that requires an RC network to produce a frequency at 2x the desired 'lock' frequency (262KHz = 524KHz), since this PLL chip has a (x/2) divider network inside.
Resistor is a tunable Pot and the Capacitor is fixed value. I already changed out the Pot for one with better thermal tolerance, and it helped, but there's still an issue.
I guess my initial question is; How much PLL drift is 'average'?
Secondary question; Should I consider a more reliable oscillator for the PLL, such as a crystal?
Thanks in advance.
PLL: http://www.ti.com/lit/ds/symlink/lmc568.pdf
I use a PLL chip that requires an RC network to produce a frequency at 2x the desired 'lock' frequency (262KHz = 524KHz), since this PLL chip has a (x/2) divider network inside.
Resistor is a tunable Pot and the Capacitor is fixed value. I already changed out the Pot for one with better thermal tolerance, and it helped, but there's still an issue.
I guess my initial question is; How much PLL drift is 'average'?
Secondary question; Should I consider a more reliable oscillator for the PLL, such as a crystal?
Thanks in advance.
PLL: http://www.ti.com/lit/ds/symlink/lmc568.pdf