3.2 Codec

The built-in codec has a high signal-to-noise ratio (SNR) performance and it consists of an Analog-to-Digital Converter (ADC), a Digital-to-Analog Converter (DAC), and an additional analog circuitry.

  • Interfaces
    • Two mono differential or single-ended microphone inputs
    • One stereo single-ended line input
    • One stereo single-ended line output
    • One stereo single-ended earphone output (capacitor-less connection)
  • Built-in circuit
    • Microphone bias (MICBIAS)
    • Reference and biasing circuitry
  • Optional digital High Pass Filter (HPF) on ADC path
  • Silence detection
    • Typically, used for Line-In inputs. For some applications, the Line-In input has high priority. After the Line-In input source is plugged in and before streaming out an audio, the Line-In noise cannot be ignored. So, the silence detection feature is used to mute this background noise.
  • Anti-pop function to reduce audible glitches
    • Pop reduction system
    • Soft Mute mode
    • Typically used when the codec analog gain is changed suddenly (for example, turning OFF the power or switching the volume dial very quickly), in which case the RCL circuits in the external audio amplifier would cause "pop" noise. The anti-pop function is used to lower or increase the gain in many small steps, 1- or 2-dB change for each step, rather than a single large gain decrease or increase.
  • ADC supports 8 kHz, 16 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz sampling rates.