CMX639 Ver la hoja de datos (PDF) - MX-COM Inc

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CMX639

Consumer / Commercial CVSD Digital Voice CODEC

MX-COM Inc  

Consumer/Commercial CVSD Digital Voice CODEC

5

CMX639 Preliminary Information

Data Enable

1

0

1

Powersave

1

don't care

0

Encoder Output

Enable

High Z (open circuit)

VSS

Table 2: Encoder Output

Clock Mode 1

input

0

0

1

1

Clock Mode 2

input

0

1

0

1

Data/Sampling Clock Rate

(Xtal/clock = f)

External Clocks

Internally generated @ f/16

Internally generated @ f/32

Internally generated @ f/64

Example for f = 1.024MHz

External Clocks

Internally generated @ 64kbps

Internally generated @ 32kbps

Internally generated @ 16kbps

Table 3: Clock Modes and Pins

3 External Components

XTAL/CLOCK

C2 C1

X1

R1

XTAL

ENCODER DATA CLOCK

ENCODER OUTPUT

DATA ENABLE

BIAS

ENCODER INPUT

1

16

2

15

3

14

4 CMX639D4 13

5

12

6

11

7

10

C4

C3

8

VSS

9

VDD

CLOCK MODE 1

CLOCK MODE 2

ALGORITHM

DECODER DATA CLOCK

DECODER INPUT

POWERSAVE

DECODER OUTPUT

VDD

C5

Figure 2: Recommended External Components for Typical Application

R1 Note 1 1MΩ ±10%

C1 Note 2 33pF ±20%

C2 Note 2 33pF ±20%

C3 Note 3 1.0µF ±20%

C4 Note 4

1.0µF

±20%

C5 Note 5

1.0µF

±20%

X1 Note 6, 7 1.024MHz

Table 4: Recommended External Components for Typical Application

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 1kΩ. Output idle channel noise levels will

improve with even lower source impedances driving the coupling capacitor’s input node.

4. Bias decoupling capacitor

5. VDD 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 VDD, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain

crystal oscillator design assistance, please consult your crystal manufacturer.

2000 MX-COM, Inc.

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480209.006

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All Trademarks and service marks are held by their respective companies.

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