High Accuracy, low-noise sigma delta DAC

Overview

The AXIOM_PULLFIRDAC is a high accuracy sigmadelta digital-to-analog converter. The low out-of-bandnoise (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_PULLFIRDAC is ideally suited for digitalto- analog conversion in front of (analog) class-D or class-AB amplifiers. In addition this IP is delivered together with up-sampling / 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.

Key Features

Dynamic range: 117 dB (20 - 20kHz)
Excellent THD performance: nTHD < -110 dBFS
Low out-of-band-noise (OOBN): -60 dBFS
Good matching properties
Robust against clock jitter
Insensitive to inter symbol interference (ISI)
Multi-bit advantages with a single bit modulator
Silicon proven in CMOS 0.14 um
Differential current outputs
High output compliance: no direct need for buffer
Area: 0.75 mm2 per channel

Block Diagram

Applications

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

Technical Specifications

Maturity

Silicon proven in CMOS 0.14 um

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