Complex Mixed-signal Circuits Research Articles

The Evolution of Integrated Interfaces for MEMS Microphones.

Over the last decade, MEMS microphones have become the leading solution for implementing the audio module in most portable devices. One of the main drivers for the success of the MEMS microphone has been the continuous improvement of the corresponding integrated interface circuit performance in terms of both dynamic range and power consumption, which enabled the introduction in mobile devices of additional functionalities, such as Hi-Fi audio recording or voice commands. As a result, MEMS microphone interface circuits evolved from just simple amplification stages to complex mixed-signal circuits, including A/D converters, with ever improving performance. This paper provides an overview of such evolution based on actual design examples, focusing, finally, on the latest cutting-edge solutions.

VHDL-AMS Modeling of Total Ionizing Dose Radiation Effects on CMOS Mixed Signal Circuits

A hierarchical method for total dose effects simulation of large mixed signal circuits using VHDL-AMS is described. Simplified behavioral models (or macro-models) of small sub-circuits replace SPICE-level circuits. The behavioral models describe the electrical circuit behavior and its dependence on the radiation dose. The behavioral models of sub-circuits can be assembled into complex mixed signal circuits. As a result, the computational cost is reduced significantly compared to conventional SPICE-based methods. The VHDL-AMS method also allows bias-dependent total dose degradation to be coupled to the circuit and operational conditions. Simulation accuracy remains sufficient to determine critical performance metrics of the circuit as the circuit performance degrades with dose.

Modelling tools built upon the hardware description language foundation

Hardware description languages (HDLs), mainly Verilog and VHDL including their analogue/mixed-signal (AMS) extensions, represent a significant investment by the electronic design automation community. HDL technology promises productivity advances, such as a medium for intellectual property exchange, model portability, model productivity, improved design collaboration, top-down design for AMS, AMS synthesis and rich mixed-level, mixed-signal simulation for improved simulation throughput. Modelling tools represent a step towards completion of the dwelling electronic design automation community's seek to build upon the HDL foundation. One such environment of tools described here is Paragon. Paragon is described and demonstrated on both behavioural models using multiple HDLs and compact device modelling applications. The various processes and modelling methodologies that are useful in designing and modelling complex mixed-signal circuits and systems are explored. The model creation processes of mixed-signal and mixed-technology systems at various levels of abstraction and hierarchy are described. Creation of compact behavioural models at a more abstract and language-independent level using these modelling methodologies is illustrated.