DS_S1D2502A01 Datasheet, PDF (50/57 Pages) Samsung semiconductor – VIDEO AMP MERGED OSD PROCESSOR FOR MONITORS

Preliminary
VIDEO AMP MERGED OSD PROCESSOR FOR MONITORS
S1D2502A01
TUNNING FACTORS OF THE S1D2502A01 PLL
• PLL External Circuit
You may follow the recommendations for PCB art work and input/output signal characteristic improvement in
recommendation.
The external circuit that has the most influence on S1D2502A01 PLL block operation is pin 3 (VCO_IN) and pin
4 (CP_OUT)'s surrounding circuit. Refer to OSD PLL block.
3
4
C1
R1
R3
R2
(option)
Figure 24. PLL External Circuit
Because the PLL circuit is basically a feedback circuit, there are many components that influence the
characteristics. C1, R1, R2, and R3 do not have a localized effect.
As you can see, they are connected to the PLL control bits and influence the characteristics through their
complicated relationships. The main functions of the time canstant and their reference values are as follows.
Table 14. Main Function of Time Constant in PLL External Circuit
Time Canstant
Recommended Value
Main Function
C1
562 (or 103, 223)
Influences the damping ratio and controls the PLL
response time
R1
5.6KΩ(7.5KΩ)
Same as C1
R2
27KΩ (or 33KΩ)
Charge pump current adjustment
R3 (Option)
30MΩ (or 20MΩ)
Extend frequency range
49