XR2212 Exar Corporation, XR2212 Datasheet - Page 11

• Manufacturer Part Number: XR2212
• Description: Precision Phase-Locked Loop
• Manufacturer: Exar Corporation

Design Instructions
The circuit of Figure 11 can be tailored to any FM
demodulation application by a choice of the external
components R
center frequency and frequency deviation, the choice of
these components can be calculated as follows, using the
design equations and definitions given on page 10.
a) Choose VCO center frequency f
b) Choose value of timing resistor R
c) Calculate value of C
Input
FM
FM carrier frequency.
of 10k
recommended value is R
of R
potentiometer, R
Figure 7 :
Rev. 2.01
0
0.1 F
is normally
2
4
to 100k . This choice is arbitrary. The
0
, R
1
, R
X
.
C
C
0
, R
0
from design equation (1) or from
= 1/R
fine-tuned with the series
5
F
, C
0
Figure 11. Circuit Connection for FM Demodulation
0
Detector
16
0
Phase
f
and C
0
20k . The final value
0
0
14
to be the same as
, to be in the range
1
. For a given FM
VCO
10
C
O
13
C
12
1
1
R
11
R
0
1
Rx Fine Tune
d) Choose R
e) Calculate C
0.1 F
V
CC
R
(see design equation 5). The tracking bandwidth, f,
should be set significantly wider than the maximum
input FM signal deviation,
tracking bandwidth to be “N” times larger than
Table 2. lists recommended values of N, for various
values of the maximum deviation of the input FM
signal.
equation 4). Normally,
Then, C
C
f
SM
9
7
, one can re-unite design equation 5 as:
11
R
1
f
F
0
= C
f
1
to determine the tracking bandwidth, f
1
0
R
R
/4 for
Reference
0
1
to set loop damping (see design
Internal
6
8
N
= 1/2.
f
f
0
SM
30pF
= 1/2 is recommended.
XR-2212
V
f
SM
CC
R
5K
. Assuming the
L
Demod
Output
0.1 F