raja.cedt wrote on Jul 17th, 2010, 3:08am:i have a basic question on PLL,
1.is it really locking phase locking or frequency locking. i feel it is making phase difference between ref and fb clock is constant at some value (normally it is zero), so frequency locking is happening. If so why Frequency Lock loop.
2. In loop filter we have RC series branch, in that r is doing phase lock and c is doing frequency locking, is this correct?
Thanks,
Rajasekhar.
1.) Of course, it depends on the kind of PD you are using.
In any case, when frequencies are different, it's a kind of frequency locking (pull-in process); if this is completed, phase locking takes over until the differece beween both phases is roughly constant (not always zero, dpends on PD).
2.) I don't understand the question. The rc combination is afilter which must attenuate unwanted products out of the PD.