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PDF CMX138A Data sheet ( Hoja de datos )
| Número de pieza | CMX138A | |
| Descripción | Audio Scrambler and Sub-Audio Signalling Processor | |
| Fabricantes | Consumer Microcircuits Limited | |
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CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX138A
Audio Scrambler and
Sub-Audio Signalling
Processor
D/138A/4 October 2014
CMX138A: Audio Scrambler and Sub-Audio Signalling Processor with Auxiliary
System Clock, ADC and DAC for use in Analogue Radio Systems
Features
Programmable Audio Scrambler
Concurrent Audio/Signalling Operations
Full Audio-band Processing:
Pre and De-emphasis, Compandor,
Scrambler and Selectable 2.55/3 kHz Filters
Auxiliary ADC and Auxiliary DAC
Selectable Audio Processing Order
Sub-audio Signalling: CTCSS, DCS
Auxiliary System Clock Output
Tx Output for Single-point Modulation
Low-power (3.0V to 3.6V) Operation
Flexible Powersave Modes
C-BUS Serial Interface to Host µController
Available in 28-pin TSSOP Package
Two Analogue Inputs (Mic or Discriminator)
DAC Output
ADC Input
3.0V to 3.6V
Modulator
Discriminator
RF
GPIO
CMX138A
Audio Scrambler
and
Sub-Audio Processor
Built on FirmASIC® technology
C-BUS
Host
µC
System Clock 1
Reference Clock
1 Brief Description
The CMX138A is a half-duplex, audio scrambler and sub-audio signalling processor IC for Analogue Two-
way Radio applications. This makes it a suitable device for the leisure radio markets (FRS, MURS,
PMR446 and GMRS).
This device provides a user programmable frequency inversion audio scrambler, companding and pre/de-
emphasis – performing simultaneous processing of Sub-audio and In-band signalling.
Other features include an auxiliary ADC channel and an auxiliary DAC interface (with optional RAMDAC,
to facilitate transmitter power ramping).
The device has flexible powersaving modes and is available in a 28-pin (E1) TSSOP package.
2014 CML Microsystems Plc
1 page  
Audio Scrambler and Sub-Audio Signalling Processor
CMX138A
2 History
Version
4
3
2
1
Changes
Updated CTCSS detector response times, following product characterisation.
Added note 74 about statistical processes.
Added description of fine attenuation settings to $CD and P4.2, P4.3
Note that it is possible to alter standard CTCSS settings when in Tx mode, but
not custom settings or DCS settings
Update MOD and AUDIO output drive parameters, after characterisation
Correct minor typos and change document status to full issue.
Enhanced description of C-BUS latency time, just before Fig 4.
Correction to Audio Tone ($CD) register, code 1100b, section 9.1.19.
Correction to Program Block 4, registers P4.10 and P4.11, section 9.2.5.
First Issue of CMX138A
Date
Oct 2014
Dec 2012
Nov 2010
Jun 2010
2014 CML Microsystems Plc
Page 5
D/138A/4
5 Page 
Audio Scrambler and Sub-Audio Signalling Processor
5.1 PCB Layout Guidelines and Power Supply Decoupling
CMX138A
1
VDEC 2
C14 C15
3
DVss
DVss Ground
Plane
4
5
6
7
DVDD
8
9
C13 C12 C11
10
DVss
DVSS
11
12
13
14
CMX138A
28
27
26 DVSS
DVSS
25
24 AVSS
AVSS
23
22
AVSS Ground
21 Plane
20
19 VBIAS
C2
18
17 AVDD
AVSS
16
C5 C3 C4
15 AVSS
Figure 3 CMX138A Power Supply Connections and De-coupling
Notes:
1. It is important to protect the analogue pins from extraneous in-band noise and to minimise the
impedance between the device and the supply and bias de-coupling capacitors. The de-coupling
capacitors should be as close as possible to the device. It is therefore recommended that the printed
circuit board is laid out with separate ground planes for the AVSS, and DVSS supplies in the area of the
CMX138A, with provision to make links between them, close to the device. Use of a multi-layer printed
circuit board will facilitate the provision of ground planes on separate layers.
2. VBIAS is used as an internal reference for detecting and generating the various analogue signals. It
must be carefully decoupled, to ensure its integrity, so apart from the decoupling capacitor shown, no
other loads should be connected. If VBIAS needs to be used to set the discriminator mid-point
reference, it must be buffered with a high input-impedance buffer.
2014 CML Microsystems Plc
Page 11
D/138A/4
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet CMX138A.PDF ] | |
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