![](http://datasheet.mmic.net.cn/Exar-Corporation/XR2211ACDTR-F_datasheet_107233/XR2211ACDTR-F_17.png)
XR-2211A
17
Rev. 1.04
c)
Calculate R1 to set the bandwidth +Df (See design equation 5):
R
1
+
R
0fO2
Df
+
20, 0001, 0002
100
+ 400K
Note: The total detection bandwidth covers the frequency range of fO +Df
d) Calculate value of C0 for a given loop damping factor:
Normally,
j = 0.5 is recommended.
C
1
+
1250
C
0
R
1
j2
+ 12505010
–9
400, 0000.52
+ 6.25pF
Increasing C1 improves the out-of-band signal rejection, but increases the PLL capture time.
e) Calculate value of the filter capacitor CD . To avoid chatter at the logic output, with RD = 470KW, CD must be:
C
D
+ 16
Df w
16
200
w 80nF
Increasing CD slows down the logic output response time.
f)
Fine tune center frequency with 5K
W potentiometer, RX.
0.1
F
RF
100K
VCC
Loop
Phase
Detect
C1
11
R1
8
FSK
Comp
.
7
3
2
1
4
11
LM324
CF
Output
Demodulated
Internal
Reference
6
LDOQ
0.1
F
10
Lock
Detect
Comp.
VCO
14
13
12
R0
C0
2
0.1
F
Input
FM
Quad
Phase
Detect
5
LDOQN
Figure 13. Linear FM Detector Using XR-2211A and an External Op Amp.
(See Section on Design Equation for Component Values.)
VCC