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High Accuracy DAC

The AXIOM FIRDAC is a high accuracy sigma-delta digital-to-analog converter. The low out-of-band-noise (OOBN) down to -60dBFS makes the converter ideally suited for application with strict OOBN requirements. The PWM modulator is a special type of 1-bit sigma-delta modulator that produces a pulse width modulated (PWM) signal with a fixed repetition frequency. A fixed repetition rate makes the output signal insensitive to non-linear inter symbol interference (ISI).

The semi-digital FIR filter topology of the FIRDAC makes the FIRDAC behave as a multi-bit DAC. This gives the converter its excellent OOBN and makes the system robust against clock jitter and other error sources typically associated with 1-bit converters while maintaining excellent THD and good matching properties.

The AXIOM_FIRDAC is ideally suited for digital-to-analog conversion in front of (analog) class-D or class-AB amplifiers. Additionally this IP can be delivered together with up-sampling and interpolation filters as signal pre-processing. The design and layout of the FIRDAC is a highly automated process, easy to scale and good portable to several CMOS technologies.


  • Excellent THD performance: THD < -110 dBFS
  • Low out-of-band-noise (OOBN): -60 dBFS
  • Dynamic range: 114 dB (20 - 20kHz)
  • Good matching properties
  • Robust against clock jitter
  • Insensitive to inter symbol interference (ISI)
  • Multi-bit advantages with a single bit modulator
  • Silicon proven in in CMOS 0.14 um
  • Multiple configurations:
    • Push-Pull or Pull
    • Single-ended or differential
  • High output compliance: no direct need for buffer
  • Area: 0.5 mm2 per channel


  • High accuracy digital-to-analog conversion with low OOBN
  • Signal generation for class-D and class-AB amplifiers
  • Audio subsystem
  • Makes a complete audio front-end system in combination with up-sampling filters and digital audio interface

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