XR2211 Exar Corporation, XR2211 Datasheet - Page 11

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

f)
V
g) Calculate Data Filter Capacitance, C
Note: All values except R
IN
minimum (peak) input voltage must exceed this value to be detected (equivalent to adjusting V threshold)
The input to the XR-2211 may sometimes be too sensitive to noise conditions on the input line. Figure 4 illustrates
a method of de-sensitizing the XR-2211 from such noisy line conditions by the use of a resistor, Rx, connected
from pin 2 to ground. The value of Rx is chosen by the equation and the desired minimum signal threshold level.
Rev. 3.01
V
IN
minimum ( peak )
R
C
sum
F
( R
( R
sum
( R
1
· Baud Rate )
F
0.25
0
R
can be rounded to nearest standard value.
R
F
1
)· R
V
R
Input
a
B
B
–V
)
Rx
b
Figure 4. Desensitizing Input Stage
V
REF
Î Î
Î Î
Î Î
F
V
Baud rate in
:
10
2
2.8 mV offset
Va
20K
seconds
11
1
V
REF
(20, 000
V
Vb
CC
20K
20, 000
To Phase
Detector
R
X
)
or R
X
20, 000
XR-2211
V
REF
V
– 1