Thanks for the advice, i am now looking at the code, and i see the changes in charge pump current, that is what i was going to look at!
It actually appears that the config. (word B) goes to the PLL three
times throughout the routine, is that right? The current seems to be: 2.3 @ start up then 0.07 for the second two cycles. I have noticed though that SLA load match is set 'asynchronuos' then 'synchronous' then 'asyncronous', is that relevant?
I put a Opamp voltage follower on the output of the PLL, but unfortunately it also replicates the AC part of the signal (the 1KHz tone).
Can you please
tell me how you arrived at the values for the input/output of the output amplifier (the 4k7,10u tan, 10k and 0.47u)? In the datasheet it says 'Depends on tuner diode characteristics': Lots of the other designs out there have the same values, did you just use common values, or has everyone copied from you? The reason i ask is that I am using BB909 diodes and i was thinking about changing the output to form a low pass filter in an attempt to just pass the DC and filter off the HF AC tone, maybe a cutoff around 100hz? I have noticed that you can change the audible tone by playing with these values, i would like to get rid of it.
I have had my oscillscope on pins 1,2,3 of the device and see a clean wave at 1, then a distorted wave and highly distorted wave at 2 and 3. I have had some success playing around at TR, TCA and TCB; reducing the value of TR and decoupling TCB to gnd via a low value resistor, this seems to reduce the phase noise a bit.
I don't think
i have grounding/RF issues becasue i have payed around with layouts so much, i have a solid ground plane, the DC is fed through chokes and the supply is smooth and well decoupled.
I really appriciate your help and if i find the answers to this little problem i will let you know so you can post them (if you would like to).