TRU050, VCXO Based PLL

Vectron International, 267 Lowell Rd, Hudson NH 03051-4916

Tel: 1-88-VECTRON-1

Page 8 of 14

Rev: 26Aug2008

Figure 7. SPICE Model

*****TRU050 ac Loop model

vi 1 0 ac 1

ri 1 0 1K

*****Phase Detector

e1 2 0 1 0 1

(for closed loop response use: e1 2 0 1 12 1)

r2 2 3 30K

c1 2 0 60p

*****Phase Detector Gain=0.53 x Data Density (Data Density=1 for clocks) for 5 volt

operation and = 0.35 * Data Density for 3.3 volt operation

e2 4 0 3 0 .35

*****Loop filter

r1 4 5 60K

c2 5 0 10p

rf 5 6 90K

cf 6 7 1.0u

e3 7 0 5 0 –10000

***** VCXO, Input Bandwidth=50kHz

r5 7 8 160K

c4 8 0 20p

*****VCXO Gain x 2pi (Example, use OUT1 x 100ppm x 2 x pi)

e4 9 0 8 0 12214

*****1/S model

r6 9 10 1000

c5 10 11 0.001

e5 11 0 10 0 –1e6

****Divide by N

e6 12 0 11 0 1

r8 12 0 1K

The bold numbers are user selectable R/C, data density, VCXO frequency and divide-

by values, and are from figure 11.

Vi

Ri

E1 R2 C1

E2 R1

C2

Rf

Cf

E3

R5 C4

E4

R6 C5

E5

E6

R7

12

3

4

5

6

7

8

9

10

11

12