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.
The specifications and measurement results are based on a silicon implementation of the IP. Specifications can be modified to meet customer requirements. Porting to several technologies is possible in a contract development project.
High accuracy sigma-delta digital-to-analog converter
Overview
Key Features
- 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, Single-ended or differential
- High output compliance: no direct need for buffer
- Area: 0.5 mm2 per channel
Benefits
- Low out-of-band noise (OOBN) without the need of a separate low-pass filter.
- Robust against clock jitter and other error sources which are typically associated bit 1-bit converters.
- The special type of PWM modulator makes the system insensitive to inter symbol interference (ISI).
- Excellent THD and good matching properties.
- The FIRDAC inherently has a “chopping-like” behavior resulting low 1/f noise.
- Since both differential input signal and bias signal are controlled by the FIRDAC, pop-free start-up can be simplified driving an audio amplifier.
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
Deliverables
- GDS file
- Behavioral model
- Netlist
- Datasheet
- Integration documentation
Technical Specifications
Foundry, Node
180nm CMOS
Maturity
The design has been silicon proven in several technologies
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