High-linearity low-resolution DACs for multi-bit oversampling - and pipelined ADCs

DACs - EC-US044

Keywords: digital to analogue conversion, analogue to digital conversion, analog-digital interfacing, high performance signal digitalisation

Start Date: 1 January 95 / Status: finished / Duration: 24 months

[ participants / contact]

Objectivies and Approach

The aim of this project is to investigate new high-precision calibration systems which can lead to a more efficient implementation of a high-linearity low-resolution DAC (digital to analogue conversion) than current solutions provide, and which can also be readily applied to such different ADC (analogue to digital conversion) architectures as oversampling multi-bit Sigma-Delta and pipeline systems. These systems should measure the absolute conversion code voltages of the main DAC, rather than the capacitance values or intercode transitions of its capacitor-array, employ a simple, robust calibration reference DAC rather than the array of capacitors as is used for conversion, and employ a sub-binary, rather than binary, code error digitisation and a corresponding code error correction to minimise silicon area.

European links: ESPRIT projects ADCIS (2196), AD2000 (5056) and MEDCHIP (7307).

Progress and Results

Low-resolution DACs with very high linearity conversion characteristics: a prototype chip has been realised in a 1.2 µm CMOS technology from Austria MikroSysteme.

High-resolution pipeline CMOS ADCs for high-speed applications: The previously devised generalised system solution has been customised for the specific architectural needs of multi-bit pipelined ADCs. A pipeline ADC with a target specification of 15 bit resolution and 5 MHz conversion frequency has been designed. The first most critical front-end stages of the pipelined ADC were designed and submitted for fabrication in a 1.0 µm CMOS technology. The complete ADC has been designed and is currently being fabricated in 0.8 m CMOS technology.

Multi-bit Sigma-Delta modulators for high-resolution DACs: A multi-bit oversampling Sigma-Delta-based DAC with a conversion resolution of 16 bits and conversion frequency of 50 MHz has been considered. The D/A converter was designed for the 1.2 µm ORBIT technology. The prototype chip is currently in fabrication at ORBIT (USA).

Information Dissemination Activities and/or Exploitation

Results obtained so far have been presented at international conferences and workshops and have been published in international journals. The list of 8 publications made within DACs may be requested from the coordinator.


Instituto Superior Tecnico
Integrated Circuits and Systems Group
Av. Rovisco Pais, 1
1096 Lisboa Codex - Portugal, P

EU Partners

Instituto Superior Tecnico, P

Non-EU Partners

Oregon State University, USA


Prof. Jose E. Franca
Tel: +351 1 841 76 75
Fax: +351 1 841 76 75
E-mail: franca@ecsm4.ist.utl.pt

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DACs - EC-US044, May 1997

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html version of synopsis by Nick Cook