XR2211 Exar Corporation, XR2211 Datasheet - Page 16

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

Design Instructions:
The circuit of Figure 12 can be optimized for any tone detection application by the choice of the 5 key circuit components:
R
(All resistance in
a) Choose value of timing resistor R
b) Calculate value of C
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
Design Examples:
Tone detector with a detection band of + 100Hz:
a) Choose value of timing resistor R
b) Calculate value of C
XR-2211
0
, R
current that the internal voltage reference can deliver. The recommended value is R
is normally fine-tuned with the series potentiometer, R
Normally, = 0.5 is recommended.
Increasing C
Increasing C
current that the internal voltage reference can deliver. The recommended value is R
is normally fine-tuned with the series potentiometer, R
Rev. 3.01
1
, C
0
C
R
C
C
C
, C
O
1
1
D
0
1
and C
1
R
1250· C
R
16
R
1
D
to set the bandwidth + f (See design equation 5):
0
R
0
1
0
f
1
improves the out-of-band signal rejection, but increases the PLL capture time.
· f
slows down the logic output response time.
· f
’s, all frequency in Hz and all capacitance in farads, unless otherwise specified)
· fs
1
f
0
S
·
·2
D
C in F
2
. For a given input, the tone frequency, f
0
0
1
0
20, 000·1, 000
from design equation (1) or from Figure 7 f
for a given loop damping factor:
from design equation (1) or from Figure 6 f
1
0
0
to be in the range of 10K
to be in the range of 10K
D
50 nF
. To avoid chatter at the logic output, with R
16
X
X
.
.
O
S
, these parameters are calculated as follows:
+ f
to 50K . This choice is dictated by the max./min.
to 50K . This choice is dictated by the max./min.
S
S
= f
= f
O
O
:
:
0
0
= 20 K . The final value of R
= 20K . The final value of R
D
= 470K , C
D
must be:
0
0