PLL loop filter selection

bandpass

As we know, the number 1 LPF in schematic is the well known circuit.
- \/ f8 \& U+ H. N( U! X
2 Y8 B) T% L! f$ {) ~3 f8 W   But some application is like the number 2 LPF in schematic. Any commetions about it ?

   Any discussion is appreciated.

circuitman5566

thank you so much! thank you so much! thank you so much!