Cmedia CM6631A is a USB2.0 true high-speed audio processor that can support the latest  USB Audio Class 2.0 and high-definition audio processing capability up to 192KHz/32bit. CM6631A provides the industrial standard I2S and HDA audio interface and also integrates 192KHz/24bit S/PDIF transmitter/receiver and MIDI I/O device. It’s suitable for versatile, high-profile, typical 2-channel I/O audio applications.

Furthermore, CM6631A has an embedded 8051 microprocessor that can enhance the best flexibility and functionality with external upgradeable F/W codes. CM6631A would be the most high-fidelity and powerful audio core for high-value USB Audio Class 2.0 products.


USB Compliance

  • USB Spec. Rev.2.0 high-speed/full-speed mode compatible
  • Latest USB Audio Device Class Definition Release v.2.0/1.0 compatible
  • USB Human Interface Device (HID) Class Definition Release 1.1 compliant
  • Supports USB suspend/resume/reset functions
  • Supports control, interrupt, bulk, and isochronous data transfers

Audio Engine

  • Max. 3 Independent Playback Streams:
    -Default Sample Rates: 44.1K/48K/88.2K/96K/176.4K/192KHz (192K/176.4KHz are available only in USB Audio Class 2.0/High-speed mode)
    -Supported Bit Length: 16/24/32 bit
    -PDMA#A and C engines support 2-channel data to I2S/HDA output
    -PDMA#B supports S/PDIF output
  • Max. 3 Independent Capture Streams:
    -Default Sample Rates: 44.1K/48K/96K/192KHz (192K/176.4KHz are available only in USB Audio Class 2.0/High-speed mode)
    -Supported Bit Length: 16/24/32 bit
    -RDMA#A and B support 2-channel data from I2S/HDA input
    -RDMA#C supports S/PDIF input (192KHz is supported only with Crystal and PLL clock source) 
    Digital mixing/routing engine to mix input streams to output streams

Audio I/O

  • 2 pairs I2S or Left-Justified serial audio output interface
  • 2 pairs I2S or Left-Justified serial audio input interface
  • Built-in 192K/176.4K/96K/88.2K/48K/44.1KHz and 16/24-bit S/PDIF transmitter
  • Integrated 192K/176.4K/96K/88.2K/48K/44.1K and 16/24-bit S/PDIF receiver
  • Supports S/PDIF IN-to-OUT loop-back path for signal transforming between TOSLINK and RCA connections

Integrated 8051 Micro-processor

  • Embedded 8051 micro-processor to handle the comment/protocol transactions
  • Connects to an external parallel Flash/EEPROM memory (Max. 64KB, 55ns access time is required) for firmware codes
  • HID interrupts can be implemented via firmware codes
  • Provides maximum HW configuration flexibility with firmware code upgrade
  • VID/PID/Product String can be customized via firmware code programming

Control Interface

  • Master I2C control interface for external audio devices or EEPROM access
  • Slave I2C control interface and interrupt pin for external MCU/device communication
  • 9 GPIO pins and 6 GPI pins
  • External device power-down control and reset pins


  • Embedded USB2.0 transceiver (up to 480MB bandwidth)
  • Auto detection for high-speed/full-speed
  • GPIO pin for USB Audio Class 2.0 and 1.0 application mode configuration
  • Provides Self-power or Bus-power mode selection pin
  • Only single 12MHz crystal input is required (embedded PLL function) or optional oscillator inputs for 49.152 or 24.576MHz (for x48KHz) and 45.158 or 22.5792MHz (for x44.1KHz)
  • Single 3.3V power supply (embedded 3.3V to 2.5V regulator for digital core)
  • 3.3V digital I/O pads with 5V tolerance
  • Industrial standard LQFP-100 package (16x16mm)
  • Supports USB Audio Class 2.0 and high-speed mode with Cmedia vendor drivers
  • USB Audio class 1.0 with full-speed/high-speed modes compatible with Windows®  UAA driver, Mac OS X and Linux embedded USB audio drivers
  • For Windows, Cmedia drivers provide the following Key Features:

             -Playback feedback endpoints to control the data transmission accuracy and to maximize the audio quality 
             -Xear™ Pro 
             -Supports ASIO2.2 driver

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