Delta Modulation CODEC
6
MX629
3 External Components
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
Figure 2: Recommended External Components for Typical Application
R1
R2
C1
C2
Note 1
Note 2
Note 3
Note 3
C3
C4
C5
X1
Note 4
Note 5
1Mꢂ
Selectable
33pF
ꢃ10%
1.0ꢄF
1.0ꢄF
ꢃ20%
ꢃ20%
ꢃ20%
Note 6
ꢃ20%
ꢃ20%
1.0ꢄF
68pF
Note 7, 8
1.024MHz
Table 4: Recommended External Components for Typical Application
Notes:
1. Oscillator inverter bias resister.
2. Xtal Drive limiting resistor.
3. Xtal circuit load capacitor.
4. Encoder input coupling capacitor. The drive source impedance to this input should be less than 100ꢂ.
Output idle channel noise levels will improve with even lower source impedance.
5. Bias decoupling capacitor
6.
V
DD
decoupling capacitor
7. A 1.024MHz Xtal/Clock input will yield exactly 16/32/64kbps data clock rates. Xtal circuitry shown is in
accordance with MX-COM’s Xtal Oscillator Application Note.
8. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at
least 40% of V , peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain
DD
crystal oscillator design assistance, please consult you crystal manufacturer.
4 General Description
The MX629 is a Continuously Variable Slope Delta Modulation (CVSD) Codec designed for use in military
communications systems. This device is suitable for applications in military delta multiplexers, switches and
phones. The MX629 is designed to meet Mil-Std-188-113 specifications.
Encoder input and decoder output filters are incorporated on-chip. Sampling clock rates can be programmed
to 16, 32, or 64kbps from an internal clock generator or externally injected in the 8 to 64kbps range. The
sampling clock frequency is output for the synchronization of external circuits.
The encoder has an enable function for use in multiplexer applications. Encoder and Decoder forced idle
capabilities are provided forcing 10101010…pattern in encode and a V /2 bias in decode. The companding
DD
circuit may be operated with an externally selectable 3- or 4-bit algorithm. The device may be placed in
standby mode by selecting Powersave. A reference 1.024MHz oscillator uses an external clock or crystal.
ꢀ1998 MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480190.001
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
All Trademarks and service marks are held by their respective companies.
CMLMICRO [ CML MICROCIRCUITS ]
