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PDF CMX618 Data sheet ( Hoja de datos )
| Número de pieza | CMX618 | |
| Descripción | RALCWI Vocoders | |
| Fabricantes | Consumer Microcircuits Limited | |
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CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX608/CMX618/
CMX638
RALCWI Vocoders
D/608_18_38/11 September 2014
Features
Near Toll Quality RALCWI Coding Algorithm
Multiple Bit Rate Modes:
2400 or 2750 bps
3600 bps with FEC Enabled
4-bit Viterbi Soft Decision Decoding
Integrated Audio CODEC (CMX618/CMX638 only)
Integrated Input and Output Channel Filters
20ms, 40ms, 60ms and 80ms Packet Lengths
No Licensing or Royalty Payments
Ancillary Audio Functions:
Voice Activity Detector
Comfort Noise Generator
DTMF and Single Tone Regeneration
1.8V Low Power Operation, 3.3V Tolerant I/O
Small 48-pin LQFP and VQFN Packages
Provisional Issue
Applications
Digital PMR, LMR, Voice Radio
Digital Trunking
DMR TDMA
DMR FDMA, dPMR
Digital Voice Scrambling and Encryption
Digital WLL
Voice Storage and Playback Systems
Regenerative Digital Voice Repeaters
Messaging Systems
VoIP Systems
Voice Pagers
Half-Duplex Vocoding (CMX608/CMX618)
Full-Duplex Vocoding (CMX638 only)
1. Brief Description
The CMX608/CMX618/CMX638 are flexible, high integration, high performance, RALCWI (Robust
Advanced Low Complexity Waveform Interpolation) Vocoders, offering near toll quality voice at very low bit
rates. A Forward Error Correction (FEC) engine provides optimum performance in real life applications.
The RALCWI Vocoder comprises four independent functions which are selectable by the host: Voice
Encoder, FEC Encoder, Voice Decoder and FEC Decoder. The CMX608 and CMX618 are half-duplex
Vocoders and the CMX638 is a full-duplex Vocoder with integrated voice CODEC.The CMX618 includes
an integrated voice CODEC, offering a complete analogue voice to low bit rate vocoded data function, with
integrated channel filters removing the need for external components, whereas the CMX608 requires an
external voice CODEC.
CMX608/CMX618/CMX638 operate from a dual power supply (1.8V and 3.3V) and are available in both
48-pin LQFP (L4) and 48-pin VQFN (Q3) packages.
Continued overleaf .....
2014 CML Microsystems Plc
1 page  
RALCWI Vocoder
2. Block Diagram
CMX608/CMX618/CMX638
Figure 1 Block Diagram
2014 CML Microsystems Plc
5
D/608_18_38/11
5 Page 
RALCWI Vocoder
4.1. PCB Layout Guidelines and Power Supply Decoupling
CMX608/CMX618/CMX638
Figure 4 CMX618/CMX638 Power Supply and De-coupling
Notes:
Component Values as per Figure 3.
It is important to protect the analogue pins from extraneous inband noise and to minimise the impedance
between the CMX618/CMX638 and the power supply and bias de-coupling capacitors. The de-coupling
capacitors C4, C6, C7, C8, C9, C10, C12, C13 and C14 should be as close as possible to the
CMX618/CMX638. It is therefore recommended that the printed circuit board is laid out with separate
ground planes for the AVSS and (digital) VSS supplies in the area of the CMX618/CMX638, with provision
to make links between them close to the CMX618/CMX638. The use of a multi-layer printed circuit board
will facilitate the provision of ground planes on separate layers. The layout of a CMX608 printed circuit
board should make use of a single ground plane covering the whole chip area shown above.
On CMX618/CMX638, 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 an external mid-
point reference, it must be buffered with a high input impedance buffer.
2014 CML Microsystems Plc
11
D/608_18_38/11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet CMX618.PDF ] | |
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