Renesas 8V19N49 Series, Manual

Page: 10 / 20

R31UH0005EU0100 Rev.1.0 Page 10
Jun 3, 2021
8V19N49x Hardware Design Guide
3.3.2 Loop Filter for VCO PLL
The 8V19N490 VCO phase lock loop diagram is displayed in Figure 11 . The Fvco frequency is 2.94912GHz. In
this example, the 2949.12MHz VCO is used. A 2
nd
order loop filter for the VCO is shown in Figure 12 .
Figure 11. VCO PLL Block Diagram
Figure 12. 2
nd
Order Loop Filter for the VCO
The board-level VCO 2nd order loop filter works in conjunction with the internal circuitries. A traditional loop filter
calculation method may not be accurate. After simulation and actual experiment, an example of external two-pole
loop filter value is provided in
Table 3 .
R3 51k Ohm 1.8k Ohm
C3 4.7nF 33nF
1. Other VCXO frequencies can also be used with proper loop filter and parameter setting. Below are examples of VCXO order information:
* 122.88MHz - Epson VG3225EFN 122.88M-CJHHBA
* 245.76MHz - Epson VG3225ENN 245.76M-CJHHMA
* 491.52MHz - Epson VG3225ENN 491.52M-CJGHSA
Table 2. Loop Filter Examples (Cont.)
Cz
Cp
Rz
LFF
LFFR