Renesas 8V19N49 Series Manual page 9

8V19N49x Hardware Design Guide
3.3.1.2 Third Order Loop Filter for the VCXO PLL
This section provides design guidelines for a 3rd order loop filter for the 8V19N490 VCXO PLL. A general 3
order loop filter is displayed in
The Rs, Cs, and Cp are chosen standard values from the 2
are Rs = 33KOhm, Cs = 1uF, and Cp = 27nF. The following equation can help determine the 3
R3 and C3.
1. Choose an R3 value. Suggest R3 ~ 1.5xRs to ~2.5xRs or greater (e.g, R3 = 51KHz is used in this example).
C3 can be calculated using the following equation:
2. Pick γ = 4 in this example.
C3 is calculated to be 4.37nF. A closest standard capacitor value can be used.
Table 2 shows some VCXO PLL Loop Filter examples for different VCXO frequencies. Other values can also be
used to meet other specific conditions and requirements.
[1]
VCXO Frequency
VCXO Made/Model Examples
Typical VCXO Gain, Kvco
Loop Bandwidth, Fc
PDF, Phase Detector Input Frequency
Feedback Divider (N or Mv)
Charge Pump Current Setting
(Can be slightly Adjusted to change
the loop band width)
Rs
Cs
Cp
R31UH0005EU0100 Rev.1.0
Jun 3, 2021
Figure 10.
LFV
Rs
Cs
Figure 10. Typical 3
Table 2. Loop Filter Examples
122.88MHz
Epson,VG4513CA/CB
Epson VG3225EFN*
Crystek CVPD922
Crystek CHPD950
Crystek CVPD-037
Rakon RVX7050M
Vectron
10k Hz/V
120kHz
33k Ohm
VCXO-VC
R3
Cp C3
rd
Order Loop Filter
nd
order loop filter. In this example, the chosen values
TXC
~40Hz
1024
800uA
1uF
27nF
rd
rd
order loop filter,
30.72MHz
Epson, TXC, Rakon
2.5k Hz/V
~40Hz
960kHz
32
800uA
1k Ohm
10uF
330nF
Page 9