EL4584CS datasheet(9/16 Pages) ELANTEC

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EL4584C

Horizontal Genlock 4 FSC

Applications Information

Choosing External Components

1 To choose LC VCO components first pick the

desired operating frequency For our example

we will use 1431818 MHz with an H-sync fre-

quency of 15734 kHz

2 Choose a reasonable inductor value (10 – 20

works well) We choose 15

3 Calculate CT needed to produce FOSC

FOSC e

0LCT

CTe

q2F2L

q2(14318e6)2(15e b 6)

82 pF

4 From the varactor data sheet find CV

25V

the desired lock voltage CVe23 pF for our

SMV1204-12 for example

5 C2 should be about 10CV

so we choose

C2e220 pF for our example

6 Calculate C1 Since

CT e

C1C2CV

(C1C2) a (C1CV) a (C2CV)

then

C1 e

C2CTCV

(C2CV) b (C2CT) b (CTCV)

For our example C1e14 pF (A trim cap may be

used for fine tuning) Examples for each frequen-

cy using the internal divider follow

Typical Application

Horizontal genlock provides clock for an analog

to digital converter digitizing analog video

Typical LC VCO

4584 – 10

Figure 10

LC VCO Component Values (Approximate)

Frequency

(MHz)

(mH)

(pF)

13301

220

135

220

1475

220

17734

220

10738

220

12273

220

14318

220

Note Use shielded inductors for optimum performance

Typical Xtal VCO

4584 – 11

Figure 11

4584 – 18

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