1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Notes
Min.
Typ.
Max.
Units
Carrier Detect
3
Sensitivity
1, 7, 8
-
-
150
mVrms
Probabilty of CD being High after bit 16:
with SNR = 12dB
9
9
0.995
0.05
with 230mVrms Noise and No Signal
Transmitter Output
Tx Output Level
Output Level Variation for 1200/1800Hz
or 1200/2400Hz or 2400/4800Hz
1
-
775
-
-
mVrms
dB
0
+/-1.0
Output Distortion
3rd Harmonic Distortion
10
10
-
-
3.0
2.0
5.0
3.0
%
%
Isochronous Distortion
1200Hz - 1800Hz/1800Hz - 1200Hz
1200Hz - 2400Hz/2400Hz - 1200Hz
2400Hz - 4800Hz/4800Hz - 2400Hz
-
-
-
25.0
20.0
10.0
40.0
30.0
20.0
µs
µs
µs
Logic ‘1’ Carrier Frequency 1200 Baud
6
6
6
6
6
6
-
-
-
-
-
-
1200
1200
2400
1800
2400
4800
-
-
-
-
-
-
Hz
Hz
Hz
Hz
Hz
Hz
2400 Baud
4800 Baud
Logic ‘0’ Carrier Frequency 1200 Baud
2400 Baud
4800 Baud
Notes:
1. Measured at V = 5.0 volts. Signal levels and thresholds are proportional to V
DD
DD.
2. Excludes any current drawn by external components, but includes current drawn by the crystal
components.
3. See Figure 6 (Typical Variation of BER with Input Signal Level).
4. SNR = Signal-to-Noise Ratio in the Bit-Rate Bandwidth.
5. See Figure 7 (Typical Rx BER vs Signal-to-Noise Ratio).
6. Dependent upon Xtal tolerance.
7. With an alternating (1010...) pattern.
8. Measured with a 150mVrms input signal (no noise).
9. A signal level of 230mVrms is used in C.D. probability measurements. Noise bandwidth is 5kHz
(1200/2400 baud operation) or 8kHz (4800 baud operation). See Section 1.4, Note 2 for details
on optimising noise immunity.
10. For an unmodulated carrier.
ã 2001 Consumer Microcircuits Limited
12
D/469A/2
CMLMICRO [ CML MICROCIRCUITS ]
