Delta Modulation CODEC
7
MX619
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
MX619 PARAMETERS
MEASURED HERE
REGULATED
POWER SUPPLY
MX619 PARAMETERS
MEASURED HERE
SYSTEM
INPUT
ANALOG
INPUT
INTERFACE
(BALUN &
BUFFER)
MX619
ENCODER
MX619
DECODER
ANALOG
OUTPUT
INTERFACE
(BALUN &
BUFFER)
SYSTEM
OUTPUT
DATA
CLOCKS
CLOCK MODE
16/32/64 KB/S
DATA
CLOCKS
1.024MHz
1.024MHz
SYNCHRONOUS CLOCK
AND DATA SYSTEM
Figure 3: System Configuration using the MX619
5.2
Digital to Analog Performance
Test
Sample
Rate
16kbps
32kbps
16kbps
32kbps
16kbps
32kbps
16kbps
32kbps
16kbps
32kbps
16kbps
32kbps
16kbps
32kbps
Bit Sequence at Decoder Input
MLA
Duty Cycle
0
0
0.05
0.05
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
0.5
0.5
Typical
Output
Level
-41.5dBmO
–42.5dBmO
-25.0dBmO
–25.0dBmO
-19.0dBmO
-18.5dBmO
-11.0dBmO
–11.5dBmO
-6.5dBmO
–6.5dBmO
-3.0dBmO
–3.0dBmO
0dBmO
0dBmO
a
b
c
d
e
f
g
10110100100100101101
1011011010101001001001001001010101101101
11011001001001001101
1011011010101001001000100100101011011011
10110101000100101011
1101101101010010001000100100101011011101
11011001000010011011
1101110110010100010000100010011010111011
11011010000010010111
111011101100100010000001001001101110111
11011010000001001111
1111011101010001000000001000101011101111
111010100000001011
1111101110100010000000000100010111011111
Table 5: Bit Sequence Test
2000
MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480189.002
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by their respective companies.
CMLMICRO [ CML MICROCIRCUITS ]
