If you put the divider bewteen the PFD nad VCO, the output of VCO is sine which will input thedivider, then you insert a circuit to make sine to square. Eg.the circuit is a OPA,and the OPA can cut the sine to square,--you may set input dc highly and load resistor(or other active load) small, so the output means square, then add buffers(inverters) to make the outout of OPA to be a ideal square.