CM108B Datasheet, PDF (4/24 Pages) C-Media Electronics – A Highly Integrated USB Audio Single Chip

CM108B
USB Audio Single Chip
1 Description and overview
The CM108B is a highly integrated single-chip USB audio solution. All essential analog modules are embedded in the
CM108B, including dual DAC and earphone driver, ADC, microphone booster, PLL, regulator and USB transceiver
modules. It is perfectly suited to USB headset, USB earphone or USB audio-interface box applications. As well, many
features are programmable with jumper pins or by external EEPROM.
The CM108B can connect to an external codec or audio DSP via I2S pins for further processing. Plus, 3 GPIO pins can
be accessed with customer application software for additional value-adding applications. In addition, audio
adjustments can be easily controlled via specific HID compliant volume control pins. Many features are
programmable with jumper pins or external EEPROM. Vendors can customize unique USB VID/PID/Product
String/Manufacture String and max/min/initial volumes to EEPROM. The CM108B also comes with an anti-pop noise
circuits design and internal oscillator which can operate without an external crystal oscillator.
2 Ordering information
Model No.
CM108B
Package
48-pin LQFP, 7mm × 7mm × 1.4mm
(plastic)
Operating Ambient
Temperature
-20°C to +70°C
Supply Range
DVdd = 5V, AVdd = 5V
3 Features
 Supports USB 2.0 full speed operation
 Compliant with USB audio device class specification 1.0
 Supports USB suspend/resume modes and remote wakeup with volume control pins
 On-chip oscillator that provides reference sources for PLL and embedded USB transceiver
 Support Xear^TM audio driver for multimedia sound effects in Windows OS, for further information please refer to
CM108B Xear^TM Audio Center Driver User’s Manual
 Jumper pin for speaker mode (playback only) or headset mode (playback plus recording)
 For headset mode, USB audio function topology has 2 input terminals, 2 output terminals, 1 mixer unit, 1 selector
unit and 3 feature units
 Jumper pin allows for mixer unit enable/disable when in headset mode
 For speaker mode, the USB audio topology has 1 input terminal, 1 output terminal and 1 feature unit
 Supports one control endpoint, one isochroous OUT endpoint, one isochroous IN endpoint, and one interrupt IN
endpoint
 Alternate zero bandwidth setting for releasing playback bandwidth on USB Bus when device is inactive
 Anti-pop noise design for device plugged and vice-versa, while A-A path is off
 Supports AES/EBU, IEC60958, S/PDIF consumer formats for stereo PCM data at S/PDIF output
 Volume up, volume down, and playback mute pins support USB HID for host control synchronization
 Record mute pin with LED indicator for record mute status
 Includes external EEPROM Interface for Vendor Specific USB VID, PID, Product String, Manufacture String, and
max/min/initial volumes
 3 GPIO pins with read/write via HID interface
 Jumper pin to set the power mode (100mA or 500mA, Bus-powered or self-powered)
 Isochronous transfer uses adaptive mode with internal PLL for synchronization
 48K/44.1KHz sampling rate for both playback and recording
 Soft mute function
Datasheet Revision: 1.11
Page 4 / 24
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