The C-Media CM108B is a highly integrated single-chip USB audio solution designed for USB headsets, headphones, audio adapters, dongles and other embedded USB audio products. It complies with USB 2.0 Full-Speed operation and USB Audio Device Class 1.0, enabling standard USB audio connectivity.
CM108B integrates the major analog and digital functions required for a USB audio design, including a dual 16-bit DAC, headphone amplifier, 16-bit ADC, microphone booster, PLL, USB transceiver, voltage regulators and anti-pop circuitry. Its crystal-less architecture allows operation without an external crystal oscillator, helping reduce external component count and PCB complexity.
The device supports 44.1kHz and 48kHz sampling rates for both playback and recording. It also provides I2S connectivity for an external codec or audio DSP and supports stereo PCM output through S/PDIF, including AES/EBU and IEC60958 consumer formats.
Integrated HID-compatible control pins support volume up, volume down, playback mute and recording mute functions. An external EEPROM interface allows customization of USB VID/PID, product information and volume settings, while programmable GPIO pins provide additional control options for customized audio products.
The CM108B operates from an external 5V supply, with the official operating range specified as 4.5V to 5.5V. It is supplied in a 48-pin LQFP package measuring approximately 7 × 7 × 1.4 mm.
Typical applications include USB headsets, USB headphones, USB sound cards, audio dongles, VoIP devices, communication terminals, gaming audio equipment and embedded USB audio systems.
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