CVSD Codec
CMX639
1.4
External Components
Figure 2 Recommended External Connections
R1
C1
C2
C3
Note 1
Note 2
Note 2
Note 3
1M
Ω
33pF
33pF
1.0
µ
F
±
10%
±
20%
±
20%
±
20%
C4
C5
X1
Note 4
Note 5
Note 6, 7
1.0
µ
F
1.0
µ
F
1.024MHz
±
20%
±
20%
Table 1 Recommended External Components
Notes:
1. Oscillator inverter bias resister
2. Xtal circuit load capacitor
3. The drive source impedance connected to the coupling capacitor’s input node, rather than the CMX639
ENCODER INPUT pin node, should be should be less than 1k
Ω
. Output idle channel noise levels will
improve with even lower source impedances driving the coupling capacitor’s input node.
4. Bias decoupling capacitor
5. V
DD
decoupling capacitor
6. A 1.024MHz Xtal/Clock input will yield exactly 16kbps/32kbps/64kbps internally generated data clock rates
7. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at least
40% of V
DD
, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain crystal
oscillator design assistance, please consult your crystal manufacturer.
©
2000
Consumer Microcircuits Limited
6
CMX639/2
CMLMICRO [ CML MICROCIRCUITS ]
