STW81100 STMicroelectronics, STW81100 Datasheet - Page 11

• Manufacturer Part Number: STW81100
• Description: MULTI-BAND RF FREQUENCY SYNTHESIZER
• Manufacturer: STMicroelectronics

www.DataSheet4U.com
where:
For a correct work of the VCO divider, B must be strictly higher than A. A can take any value ranging from
0 to 63. The range of the N number can vary from 4096 to 32767.
Figure 13. VCO Divider Diagram
7.5 Phase frequency detector (PFD)
The PFD takes inputs from the reference and the VCO dividers and produces an output proportional to
the phase error. The PFD includes a delay gate that controls the width of the anti-backlash pulse. This
pulse ensures that there is no dead zone in the PFD transfer function.
Figure 6 is a simplified schematic of the PFD.
Figure 14. PDF Diagram
– FVCO: output frequency of VCO.
– P: modulus of dual modulus prescaler.
– B: division ratio of the main counter.
– A: division ratio of the swallow counter.
– Fref: input reference frequency.
– R: division ratio of reference counter.
– N: division ratio of PLL
VCOBUF+
VCOBUF+
VCOBUF-
VCOBUF-
VDD
VDD
Fref
Fref
VDD
VDD
Fref
Fref
A counter
A counter
Prescaler
Prescaler
64/65
64/65
6 bit
6 bit
D FF
D FF
D FF
D FF
R
R
modulus
modulus
R
R
Delay
Delay
ABL
ABL
Down
Down
Up
Up
B counter
B counter
9 bit
9 bit
To PFD
To PFD
STW81100
11/23