EL4584 データシートの表示（PDF） - Renesas Electronics
部品番号
コンポーネント説明
一致するリスト
EL4584 Datasheet PDF : 15 Pages
| |||
EL4584
The resistance needed will depend on VCO design or VCXO
module selection.
Applications Information
Choosing External Components
1. To choose LC VCO components, first pick the desired
operating frequency. For our example, we will use
14.31818MHz, with an HSYNC frequency of 15.734kHz.
2. Choose a reasonable inductor value (10µH to 20µH
works well). We choose 15µH.
3. Calculate CT needed to produce FOSC, as shown in
Equations 1 and 2.
FOSC
=
----------1------------
2 LCT
(EQ. 1)
CT = 4--------2--1-F----2---L-- = 4--------2------1---4---.--3---1----8---e--1--6------2------1---5----e-----–-----6---- = 8.2pF
(EQ. 2)
4. From the varactor data sheet find CV @ 2.5V, the desired
lock voltage. CV = 23pF for our SMV1204-12, for
example.
5. C2 should be about 10CV, so we choose C2 = 220pF for
our example.
6. Calculate C1 using Equations 3 and 4. Since:
CT = ---C----1----C----2-------+-----C---C-1---1-C---C-2---V-C----V---+-------C----2----C----V-------
(EQ. 3)
then:
C1 = ---C-----2---C----V-------–---C---C--2--2-C--C---T--T--C----V-–-------C-----T---C-----V------
(EQ. 4)
For our example, C1 = 14pF (a trim capacitor may be used
for fine tuning). Examples for each frequency using the
internal divider follow.
Typical Application
Horizontal genlock provides clock for an analog to digital
converter, digitizing analog video.
FIGURE 12. TYPICAL LC VCO
TABLE 3. LC VCO COMPONENT VALUES (APPROXIMATE)
(NOTE)
FREQUENCY
L1
C1
C2
(MHZ)
(µH)
(pF)
(pF)
13.301
15
18
220
13.5
15
17
220
14.75
12
18
220
17.734
12
10
220
10.738
22
20
220
12.273
18
17
220
14.318
15
14
220
NOTE: Use shielded inductors for optimum performance.
FIGURE 11.
FN7174 Rev 3.00
May 9, 2008
FIGURE 13. TYPICAL XTAL VCO
TABLE 4. XTAL VCO COMPONENT VALUES
(APPROXIMATE)
FREQUENCY
R1
C1
(MHz)
(k)
(pF)
13.301
300
15
13.5
300
15
14.75
300
15
C2
(µF)
0.001
0.001
0.001
Page 9 of 15
Share Link: 