Marine VHF Audio and Signalling Processor
CMX885
9.1.4 Parametric Performance
For the following conditions unless otherwise specified:
External components as recommended in Figure 2.
Maximum load on digital outputs = 30pF.
Xtal Frequency = 3.6864MHz±0.003% (30ppm)§; Tamb = −40°C to +85°C.
AVDD = DVDD = 3.0V to 3.6V.
Reference Signal Level = 308mVrms at 1kHz with AVDD = 3.3V.
Signal levels track with supply voltage, so scale accordingly.
Signal to Noise Ratio (SNR) in bit rate bandwidth.
Input stage gain = 0dB, Output stage attenuation = 0dB.
AC Parameters
DSC Decoder
Notes
Min.
Typ.
Max.
Unit
Signal Input Dynamic Range
Bit Error Rate
Co-channel Rejection
Bit Rate Sync Time
81
81
100
–
–
–
<1
10
2
800
–
–
mVrms
10-2
dB
(SNR = 8dB)
–
–
edges
DTMF Decoder
Sensitivity
Response Time
De-response Time
Falsing Rate (per 30min voice input)
Frequency Tolerance
Twist
–
–
–
–
–
+3
–
45
–
–
+10
dB
ms
ms
−22
35
–
10
±2.5
–
%
dB
−10
NWR Decoder
Sensitivity
–
TBD
–
dB
Inband Tone Encoder
Frequency Range
288
–
−1.0
–
–
–
0
3000
±0.3
+1.0
4.0
Hz
%
dB
Tone Frequency Accuracy
Tone Amplitude Tolerance
Total Harmonic Distortion
83
82
2.0
%
DTMF Encoder
Output Signal Level
Output Level Variation
Output Distortion
84
–
–
–
775
± 0.5
–
–
–
5
mVrms
dB
%
DSC Encoder
Output Signal Level
Output Distortion
3rd Harmonic Distortion
Logic 1 Frequency
Logic 0 Frequency
Baud Rate
–
–
–
–
–
–
–
775
–
–
1300
2100
1200
6
–
5
3
–
–
–
–
mVrms
%
%
Hz
Hz
bps
dB
Pre-emphasis
(per octave)
§
81
To meet DSC specifications, a 30ppm xtal, or better, is required.
AVDD = 3.3V, for a “101010101 … 01” pattern measured at the input amplifier
Notes:
feedback pin. Signal level scales with AVDD
.
82
83
84
Measured at MOD1 or MOD2 output.
AVDD = 3.3V and Tx Audio Level set to 871mV p-p (308mVrms).
AVDD = 3.3V. Measured in single tone mode, P1.0 set to $2FFE.
© 2010 CML Microsystems Plc
65
D/885/3
CMLMICRO [ CML MICROCIRCUITS ]
