Digital-to-analog Converter - DAC Figures of Merit

DAC Figures of Merit

  • Static performance:
    • Differential nonlinearity (DNL) shows how much two adjacent code analog values deviate from the ideal 1 LSB step.
    • Integral nonlinearity (INL) shows how much the DAC transfer characteristic deviates from an ideal one. That is, the ideal characteristic is usually a straight line; INL shows how much the actual voltage at a given code value differs from that line, in LSBs (1 LSB steps).
    • Gain
    • Offset
    • Noise is ultimately limited by the thermal noise generated by passive components such as resistors. For audio applications and in room temperatures, such noise is usually a little less than 1 μV (microvolt) of white noise. This limits performance to less than 20~21 bits even in 24-bit DACs.
  • Frequency domain performance
    • Spurious-free dynamic range (SFDR) indicates in dB the ratio between the powers of the converted main signal and the greatest undesired spur.
    • Signal-to-noise and distortion ratio (SNDR) indicates in dB the ratio between the powers of the converted main signal and the sum of the noise and the generated harmonic spurs
    • i-th harmonic distortion (HDi) indicates the power of the i-th harmonic of the converted main signal
    • Total harmonic distortion (THD) is the sum of the powers of all HDi
    • If the maximum DNL error is less than 1 LSB, then the D/A converter is guaranteed to be monotonic. However, many monotonic converters may have a maximum DNL greater than 1 LSB.
  • Time domain performance:
    • Glitch impulse area (glitch energy)
    • Response uncertainty
    • Time nonlinearity (TNL)

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