The CM6635 is a USB 2.0 high speed audio controller that complaints with USB Audio Device Class 2.0. The CM6635 provides standard I2S and S/PDIF digital audio interface. The maximum outputs are 6 channels with 4 channels I2S and 2 channels S/PDIF and the maximum inputs are 6 channels with 4 channels I2S and 2 channels S/PDIF. The first I2S interface can be used to transfer PCM and DSD audio data. Moreover, the CM6635 supports I2C, SPI and GPIOs to communicate with external device.
The CM6635 is embedded with 8051 MCU and 512KB flash makes it is very flexible to change the USB topology or communicate with external device by changing internal flash code.

USB Compliance

  • Compliant with USB 2.0 high-speed
  • Compliant with USB Audio Device Class 2.0/1.0
  • Compliant with USB Human Interface Device (HID) Class 1.1
  • Supports USB suspend/resume/reset functions
  • Supports control, interrupt, bulk, and isochronous data transfers
  • USB audio is asynchronous synchronization to reduce clock jitter

Integrated 8051 Micro Processor

  • Embedded 8051 micro-processor handles the USB transfers(control, isochronous, interrupt, and bulk)
  • Communicate with external peripheral devices(I2C, I2S, SPI, GPIO, etc.)
  • The MCU speed is programmable from 3.072 ~65.536 MHz
  • HID interrupts can be implemented via firmware codes
  • Provides maximum HW configuration flexibility with a firmware code upgrade
  • VID/PID/product string can be customized via firmware code programming

Control Interface

  • 1 Master I2C control interface to communicate with external devices or EEPROM, the master I2C speed supports standard mode(100KHz) and fast mode(400KHz)
  • 1 Slave I2C control interface for external MCU communication, the slave I2C speed supports standard mode(100KHz) and fast mode(400KHz)
  • 1 SPI master, supports speed from 32.768M ~ 0.3695Mb/s
  • 1 UART
  • 18 GPIOs(programmable multi functions I/O), 6 XDs(can be GPIO or other functions)
  • 6 PWM LED driver output


  • Embedded USB 2.0 transceiver and power-on reset circuit.
  • Bus-power and self-power options
  • Single 12MHz crystal input is required (embedded PLL function), or optional oscillator inputs for 49.152 or 24.576MHz (for x48KHz audio format) and 45.158 or 22.5792MHz (for x44.1KHz audio format)
  • 12 MHz clock output for external devices.
  • Single 5V power supply with embedded 5V to 3.3V regulator.
  • Auto detection for high-speed/full-speed
  • 3.3V digital I/O pads with 5V tolerance
  • Compliant with USB IF certification requirements.
  • QFN-64 package (7.5 x 7.5 mm)

Optional Value-added Software Features

  • Xear™ Pro- ASIO2.2 driver
  • Native DSD by ASIO