3.2 Codec

The built-in codec has a high SNR performance and it consists of an ADC, a DAC and an additional analog circuitry. The internal codec supports 20-bit resolution for DAC and 16-bit resolution for ADC.

  • Interfaces
    • Two mono differential or single-ended MIC inputs
    • One stereo single-ended line input
    • One stereo single-ended line output
    • One stereo single-ended headphone output (capacitor-less connection)
  • Built-in circuit
    • MIC bias
    • Reference and biasing circuitry
  • Optional digital High Pass Filter (HPF) on ADC path
  • Silence detection
    • To turn off the DSP and audio codec subsystem, if there is no Line-In data after UI configured time stamp.
  • Anti-pop function (pop reduction system to reduce audible glitches)
  • Sampling rates:
    • ADC/DAC/I2S: 8 kHz, 16 kHz, 44.1 kHz, and 48 kHz
Note: The sampling rates can be selected in the CODEC Setup tab of Config Tool.

DAC Performance

The audio graphs in this section are produced in the following conditions:
  • At room temperature
  • Using BM83 EVB platform with BM83 module mounted on BM83 Carrier Board
  • Input signal = 1 kHz sine tone, level sweep across -100 dBv to 6 dBv, frequency sweep across 20 Hz to 20 kHz at 1 Fs input level
  • Various termination loads (16Ω, 32Ω, 100 kΩ)
  • Analog gain = -3 dB; digital gain = 0 dB
  • A-weighting applied, 22K bandwidth.
The following figures illustrate the DAC performance.
Figure 3-4. Gain Vs. Input Level at Various Loads (Capless Mode)
Figure 3-5. Gain Vs. Input Level at Various Loads (Single-ended Mode)
Figure 3-6. Gain Vs. Frequency at Various Loads (Capless Mode)
Figure 3-7. Gain Vs. Frequency at Various Loads (Single-ended Mode)
Figure 3-8. Level Vs. Frequency at Various Loads (Capless Mode)
Figure 3-9. Level Vs. Frequency at Various Loads (Single-ended Mode)
Figure 3-10. THD Ratio (%) Vs. Input Level at Various Loads (Capless Mode)
Figure 3-11. THD Ratio (dB) Vs. Input Level at Various Loads (Capless Mode)
Figure 3-12. THD+N Ratio (%) Vs. Input Level at Various Loads (Capless Mode)
Figure 3-13. THD+N Ratio (dB) Vs. Input Level at Various Loads (Capless Mode)
Figure 3-14. THD+N Ratio (%) Vs. Input Level at Various Loads (Single-ended mode)
Figure 3-15. THD+N Ratio (dB) Vs. Input Level at Various Loads (Single-ended mode)
Figure 3-16. THD+N Ratio (%) Vs. Output Level at Various Loads (Capless Mode)
Figure 3-17. THD+N Ratio (dB) Vs. Output Level at Various Loads (Capless Mode)
Figure 3-18. THD+N Ratio (%) Vs. Output Level at Various Loads (Single-ended mode)
Figure 3-19. THD+N Ratio (dB) Vs. Output Level at Various Loads (Single-ended mode)

ADC Performance

The audio graphs in this section were produced in the following conditions:
  • At room temperature
  • Using BM83 EVB platform with BM83 module mounted on BM83 Carrier Board
  • Input signal = 1 kHz sine tone, level sweep across -100 dBv to 6 dBv, frequency sweep across 20 Hz to 20 kHz at 1 Fs input level
  • Analog gain = -3 dB; digital gain = 0 dB
  • A-weighting applied, 22K bandwidth
The following figures illustrate the ADC performance.
Figure 3-20. Gain Vs. Input Level
Figure 3-21. Gain Vs. Frequency
Figure 3-22. Output Level Vs. Input Level
Figure 3-23. Level Vs. Frequency
Figure 3-24. THD+N Ratio (%) Vs. Input Level
Figure 3-25. THD+N Ratio (dB) Vs. Input Level
Figure 3-26. THD+N Ratio (%) Vs. Output Level
Figure 3-27. THD+N Ratio (dB) Vs. Output Level
Figure 3-28. THD+N Ratio (%) Vs. Frequency
Figure 3-29. THD+N Ratio (dB) Vs. Frequency