CVSD Codec
CMX639
Dynamic Values
Encoder:
Notes
Min.
Typ.
Max.
Units
Analog Signal Input Levels
VDD = 3.0V
7
7
-37
-33
6
dB
dB
Hz
Hz
ms
VDD = 5.0V
10
Principal Integrator Frequency
Encoder Passband
Compand Time Constant
Decoder:
160
3240
5
4
Analog Signal Output Levels
VDD = 3.0V
7
7
4
-37
-33
6
dB
dB
Hz
VDD = 5.0V
10
Decoder Passband
Encoder Decoder (Full Codec):
Passband
3200
4
300
6
3400
10
Hz
kHz
dB
Stopband
Stopband Attenuation
Passband Gain
60
0
dB
Passband Ripple
-3.0
3.0
dB
Output Noise (Input Short Circuit)
Perfect Idle Channel Noise
(Encode Forced)
8
-60
-63
dBm0p
8, 9
5
dBm0p
Group Delay Distortion
(1000Hz - 2600Hz)
(600Hz - 2800Hz)
(500Hz - 3000Hz)
Xtal/Clock Frequency
450
750
ms
ms
1500
2.048
ms
MHz
10, 11
0.500
1.024
Notes:
1. All logic inputs except Encoder and Decoder Data clocks.
2. The source impedance driving the coupling capacitor should be less than 1kW. A lower driving source
impedance will reduce encoder output channel noise levels.
3. For an Encoder/Decoder combination.
4. See Figure 5.
5. Group Delay Distortion for the full codec is relative to the delay with an 820Hz, -20dB signal at the encoder
input.
6. Not including any current drawn from the device pins by external circuits.
7. Recommended values.
8. dBm0p units are measured after the application of a psophometrically weighted filter that is commonly
applied in voice communication applications per CCITT Recommendation G.223.
9. Forced idle encode/decode control not available on D4 (16-pin SOIC) package.
10. Some applications may benefit from the use of an Xtal/Clock frequency other than 1.024MHz.
Note: Codec time constants and filter response curves are effectively proportional to Xtal/Clock frequency
ã 2000 Consumer Microcircuits Limited
10
CMX639/2
CMLMICRO [ CML MICROCIRCUITS ]
