XR2211 Exar Corporation, XR2211 Datasheet - Page 17

• Manufacturer Part Number: XR2211
• Description: FSK Demodulator/ Tone Decoder
• Manufacturer: Exar Corporation

c) Calculate R
Note: The total detection bandwidth covers the frequency range of f
d) Calculate value of C
e) Calculate value of the filter capacitor C
f)
FM
Input
Normally,
Increasing C
Increasing C
Fine tune center frequency with 5K
Rev. 3.01
0.1 F
R
C
C
2
1
1
D
1
R
= 0.5 is recommended.
1250· C
16
1
D
to set the bandwidth + f (See design equation 5):
0
R
f
improves the out-of-band signal rejection, but increases the PLL capture time.
· f
slows down the logic output response time.
1
O
f
·
·2
2
Figure 13. Linear FM Detector Using XR-2211 and an External Op Amp.
Detect
Quad
Phase
Phase
Detect
0
200
Loop
16
0
for a given loop damping factor:
14
20, 000·1, 000·2
400, 000·0.5
1250·50·10
(See Section on Design Equation for Component Values.)
80 nF
VCO
11
100
C
0
13
C
1
12
– 9
2
potentiometer, R
D
. To avoid chatter at the logic output, with R
R
R
6.25 pF
1
0
400 K
V
0.1 F
CC
10
8
17
X
.
+
+
O
Lock
Detect
Comp.
+ f
Reference
Internal
Comp
.
FSK
7
6
5
LDOQ
LDOQN
100K
R
F
C
F
3
2
D
V
+
CC
= 470K , C
4
1 1
XR-2211
LM324
1
0.1 F
D
must be:
Demodulated
Output