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PDF CMX148 Data sheet ( Hoja de datos )
| Número de pieza | CMX148 | |
| Descripción | PMR Audio and Data Processor | |
| Fabricantes | Consumer Microcircuits Limited | |
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CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX148
PMR Audio and Data Processor
D/148/6 November 2010
Audio Processing, DTMF and FFSK/MSK Data Modem
with Auxiliary Functions for use in Analogue PMR Systems
Features
• Concurrent Audio/Signalling/Data Operations
• Complete Audio-band Processing:
o Selectable Audio Processing Order
o Pre and De-emphasis
o Selectable 2.55/3.0 kHz Filtering
o Selectable Audio HPF Cut-off
o Compandor
o Limiter
• Programmable Voice Scrambler
• MSK/FFSK Data Modem with Packet or Free-
format Modes with FEC, CRC, Interleaving and
Scrambling
• DTMF and Audio Tone Encoder/Decoder
• Routing to Support Host µController Signalling
• Sub-Audio Signalling Filters for CTCSS and DCS
• Dual Auxiliary ADC, 4 Multiplexed Inputs
• 4 x Auxiliary DACs
• Dual Programmable System Clock Outputs
• Tx Outputs for Single, Two-Point or I/Q
Modulation
• Microphone and Discriminator Analogue
Inputs
• Digital Gain Adjustment
• Default 3.6864MHz Xtal/Clock
• C-BUS Serial Interface to Host µController
• Flexible Powersave Modes
• Low-power 3.3V Operation
• Small VQFN and LQFP Packages
Host µC
Audio Out
Mic Input
Filtered Signal for Host Decoding
Host Generated Signalling
IRQ
C-BUS
Reference Clock
3.3V Supply
CMX148
PMR Voice and Data
Processor
Auxiliary
Multiplexed
ADC Inputs
Auxiliary
DACs
Modulator
Discriminator
Tx Enable
Rx Enable
System Clock 1
System Clock 2
RF
1. Brief Description
The CMX148 is a half-duplex, audio, signalling and data processing IC for use in PMR systems that utilise
the host µC to perform signalling, including CTCSS/DCS encoding/decoding. The device is intended for
use in general leisure and professional PMR terminals.
Comprehensive audio processing facilities include complete audio processing, filtering, companding, pre-
or de-emphasis and frequency inversion scrambling. The CMX148 features an FFSK/MSK data modem
for packetised or free-format data operations. Signal routing and filtering is included to assist host µC
based signal encoding/decoding applications.
A DTMF encoder/decoder, a full complement of auxiliary ADCs and DACs and dual synthesised clock
outputs are included in this low power PMR processor. The device also has flexible powersaving modes
and is available in 48-pin VQFN and LQFP packages.
© 2010 CML Microsystems Plc
1 page  
PMR Audio and Data Processor
CMX148
1.1. History
Version
6
5
2-4
1
Changes
•
• Removal of spurious notes 32 and 33, section 9.1.3
• Enhanced description of C-BUS latency time, just before Fig 4.
• Correction to Audio Tone ($CD) register, code 1100b, section 8.1.29.
• Correction to Program Block 4, registers P4.7, P4.10, P4.11, section 8.2.5.
• First documentation release
• Internal documentation updates
• Initial document created – based on 7031/7041FI-1.3 documentation
Date
25 Nov 10
09 Jul 09
11 Mar 09
02 Jul 08
© 2010 CML Microsystems Plc
5
D/148/6
5 Page 
PMR Audio and Data Processor
5. PCB Layout Guidelines and Power Supply Decoupling
C3
DVSS
C20+
C21
DVSS
DVSS
VDEC
DVDD
DVDD
C22
DVSS DVSS
DVSS
DVSS
1
2
3
4
5
6
7
8
9
10
11
12
AVDD
AVSS
C17+
C18 C19
AVSS
AVSS
AVSS
Analogue Ground Plane
C7
AVSS
CMX148 (Q3/L4)
36
35
34 AVSS
33
32
31
30
29
28
27
26 DVSS
25
AVSS
DVSS
CMX148
Digital Ground Plane
C24+ C23
DVSS
DVSS
Figure 3 Power Supply and Decoupling
Notes:
Component Values as per Figure 2.
It is important to protect the analogue pins from extraneous inband noise and to minimise the impedance
between the device and the supply and bias decoupling capacitors. The decoupling capacitors C3, C7,
C18, C19, C21, C22, C24 and C25 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 CMX148, 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.
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.
The single ended microphone input and audio output must be ac coupled (as shown), so that their return
paths can be connected to AVSS without introducing dc offsets. Further buffering of the audio output is
advised.
The crystal X1 may be replaced with an external clock source.
© 2010 CML Microsystems Plc
11
D/148/6
11 Page | ||
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