Wireless Systems Design

Audio Codec Targets Digital Voice And Audio

The CMX649 compact, low-power, multimode audio-codec IC is now available to customers. Targeted specifically at the wireless digital-voice/audio-communications marketplace, this device offers full-duplex ADM (CVSD) and PCM (linear and A-law) modes. Consequently, it is ideal for a range of consumer-based applications, such as cordless headsets, cordless telephones, digital voice storage/playback, and telematics voice-recognition systems.

Drawing a mere 1.9 mA at 2.7 V, the CMX649 works to extend battery life. Integrated functions eliminate the need for external circuits. These circuits include a digital signal processor (DSP), audio gain, sidetone, microphone amplifier, audio filters, and phase-locked-loop (PLL) data clock recovery. With its serial interface, the CMX649 also reduces the cost, size, and design effort required to interface audio signals to digital wireless transceivers. Independent Tx and Rx "power-save" modes support lowest-power operation in all modes.

The various CMX649 operating modes and algorithms are user configured to select the best data rate and voice quality for each application. Robust ADM coding (e.g., CVSD) reduces host protocol and software burdens by eliminating forward error correction (FEC), framing protocols, and algorithm processing. Acceptance of the CVSD algorithm has been widely promoted by its inclusion in the Bluetooth standard. One CMX649 CVSD mode provides 64-kbps coding in support of Bluetooth-compatible customer designs.

CMX649 features include a programmable voice activity detector (VAD) with adjustable threshold level and attack/decay times. It also houses a transcoder and a selectable digital scrambler for coded signal privacy.

The CMX649 is now available. It comes in a 20-pin TSSOP package.

CML Microcircuits (USA), Inc.
4800 Bethania Station Rd., Winston-Salem, NC 27105; (336) 744-5050, FAX: (336) 744-5054, www.cmlmicro.com.

TAGS: Digital ICs
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