LMX2325 datasheet(17/22 Pages) NSC

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Application Information (Continued)

Consider the following application examples

Example

KVCO e 20 MHzV

Kw e 5 mA (Note 1)

RFopt e 900 MHz

Fref e 200 kHz

N e RFopt fref e 4500

0p e 2q 20 kHz e 1256e5

wp e 45

ATTEN e 20 dB

T1 e

secwp b tanwp

329eb6

T3 e

010(2020)b1

(2q

200e3)2

2387eb6

0c e

(329eb6 a 2387eb6)

(329eb6 a 2387eb6)2 a 329eb6

2387eb6

01a(329eb6a2387eb6)

2 a 329eb6 2387eb6

(329eb6 a 2387eb6) 2

(

7045e4

T2 e

(7045e4)2

(329eb6 a 2387eb6)

3549eb5

C1 e

329eb6

3549eb5

(5eb3)

20e6

(7045e4)2

4500

1 a (7045e4)2

(3549eb5)2

1 a (7045e4)2

(329eb6)2 1 a (7045e4)2 (2387eb6)2

(

1085 nF

C2 e 1085 nF

355eb5

329eb6

J e106nF

R2 e

355eb5

106eb9

335 kX

if we choose R3 e 22k then C3 e

234eb6

22e3

106 pF

Converting to standard component values gives the follow-

ing filter values which are shown in

Figure 4

C1 e 1000 pF

R2 e 33 kX

C2 e 10 nF

R3 e 22 kX

C3 e 100 pF

Note 1

See related equation for Kw in Charge Pump Current Specification

Definitions For this example VP e 50V The value of Kw can then

be approximated using the curves in the Typical Peformance Char-

acteristics for Charge Pump Current vs Do Voltage The units for

Kw are in mA You may also use Kw e (5 mA2q rad) but in this

case you must convert KVCO to (radV) multiplying by 2q

TLW12339 – 46

FIGURE 4 E20 kHz Loop Filter

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