Delta Modulation CODEC
7
MX629
5 Application
Due to the very low levels of a signal idle channel noise specified for military applications, a noisy or badly
regulated power supply could cause instability, putting the overall system performance out of specification.
Adherence to the points listed below will assist in minimizing this problem.
1. Care should be taken in the design and layout of the printed circuit board.
2. All external components (as recommended in Figure 2) should be kept close to the package.
3. Tracks should be kept short, particularly the Encoder Input capacitor and the V
BIAS
capacitor.
4. Xtal/Clock tracks should be kept well away from analog inputs and outputs.
5. Inputs and outputs should be screened whenever possible.
6. A ‘ground plane’ connected to V
SS
will assist in eliminating external pick-up on the input and output pins.
7. It is recommended that the power supply rails have less that 1mV
RMS
of noise allowed.
8. The source impedance to the Encoder Input pin must be less that 100W; output idle channel, noise levels
will improve with even power source impedances.
5.1
CODEC Integration
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Figure 3: System Configuration using the MX629
5.2
Digital to Analog Performance
Bit Sequence at Decoder Input
11011011010010010010
1101101101010100100100100100101010110110
1111101101000010010
1111110110101010000100000010010101011110
‘Run of Threes’ (%)
0
0
30
30
Output level (dBm0)
-29.22
-30.02
01
01
Sample Rate
16kbps
32kbps
16kbps
32kbps
Table 5: Bit Sequence Test and Results
1998
MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
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Doc. # 20480190.001
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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CMLMICRO [ CML MICROCIRCUITS ]
