Miniature Wireless ADM Voice Codec from CML Offers Low Power Consumption and Quality Voice Reproduction

The distinguishing features of the CMX649 are the advanced error tolerant voice coding and industry leading low power consumption (drawing an operational 1.9mA at 2.7V), with advanced power-saving options to further battery life conservation in miniature cordless applications, such as ‘in-ear’ hands-free headsets.



The CMX649 offers full-duplex ADM, Continuously Variable Slope Delta Modulation (CVSD) and PCM (linear, A‑law, µ(mu)‑law and linear) operating modes. Operating modes and algorithms are user-configurable, so as 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 the need for forward-error-correction, framing protocols and algorithm processing. Acceptance of the CVSD algorithm has been widely promoted by its inclusion in the Bluetooth™ standard. One particular CMX649 CVSD mode provides 64kb/s coding to support Bluetooth™‑ compatible designs.



Independent Tx and Rx powersave modes also support lowest power operation in all modes. The product’s ability to ‘tune’ the majority of on-chip sections, provides reduced power consumption allowing product design engineers to develop optimal power-requirement strategies tailored to specific applications.



Integrated on-chip functions eliminate the need for external circuits, including DSP, audio-gain, sidetone, mic-gain, audio filtering and PLL data clock recovery. With its popular C-BUS serial interface, the CMX649 reduces the cost, size and design effort required to interface analogue ‘voice’ signals to digital wireless transceivers.



Additional CMX649 features include a programmable voice activity detector (VAD) with adjustable threshold level and attack/decay times, a transcoder to convert between different voice coding schemes and a selectable digital scrambler for coded signal privacy and efficiency in modulation.



The CMX649 is available in compact 20-pin plastic SOIC and TSSOP packages, and an evaluation kit is available (DE6491 Wireless Voice Link Demonstration Kit).