XR-2211A Datasheet, PDF (13/24 Pages) Exar Corporation – FSK Demodulator/ Tone Decoder

XR-2211A
Design Example:
1200 Baud FSK demodulator with mark and space frequencies of 1200/2200.
Step 1: Calculate f_O: from design instructions
(a) f_O + ^Ǹ1200·2200 =1624
Step 2: Calculate R₀ : R₀ =10K with a potentiometer of 10K. (See design instructions (b))
ǒ Ǔ _(b)
R_T + 10 )
10
2
+ 15K
Step 3: Calculate C₀ from design instructions
(c)
C_O
+
1
15000·1624
+ 39nF
Step 4: Calculate R₁ : from design instructions
(d)
R₁
+
20000·1624·2
(2200–1200)
+ 51, 000
Step 5: Calculate C₁ : from design instructions
(e)
C₁
+
1250·39nF
51000·0.5²
+ 3.9nF
Step 6: Calculate R_F : R_F should be at least five times R₁, R_F = 51,000⋅5 = 255 KW
Step 7: Calculate R_B : R_B should be at least five times R_F, R_B = 255,000⋅5 = 1.2 MW
Step 8: Calculate R_{SUM :}
R_SUM
+
(R_F ) R₁)·R_B
(R_F ) R₁ ) R_B)
+ 240KW
Step 9: Calculate C_{F :}
C_F
+
250
ǒ_RSUM·Baud
Rate^Ǔ
+ 1nF
Note: All values except R₀ can be rounded to nearest standard value.
Rev. 1.01
13