AN ULTRA WIDE TEMPERATURE RANGE R-2R BASED 8 BIT D/A CONVERTER FOR 90NM CMOS TECHNOLOGY
Muhammet Burak Baran
Electronics Engineering, MSc. Thesis, 2012
Prof. Dr. Yaşar Gürbüz (Thesis Supervisor), Assoc. Prof. Meriç Özcan, Asst. Prof. Cem Öztürk, Asst. Prof. Volkan Özgüz, Asst. Prof. Hüsnü Yenigün
Date & Time: August 6th 2012 – 13:00
Place: FENS L055
Keywords: DAC, cryogenic circuits, UWT, CMOS D/A converter, R-2R
Digital-to-analog converters have a wide range of applications from converting stored digital/audio signals to data processing and to data acquisition systems. Another application area could be a supporting building block in either cooled or un-cooled Read-out integrated circuits (ROICs). For this aspect, the capability of ultra wide temperature range operation may prove useful providing freedom to the designer and the consumer.
In this thesis, design of an 8-bit, fully binary R-2R based digital-to-analog converter is realized with 90nm CMOS technology to operate in a wide temperature range (-200◦C to 120◦C) to be used in an ongoing Digital Read-out Integrated Circuit (DROIC) project. UWT range of operation is obtained via a temperature compensated voltage reference generator circuit consisting of only MOSFETs. In order to aid the matching of the resistors, a common-centroid layout technique is applied to the resistor core of the circuit which eliminates the process gradients. TSMC’s 90nm 1 poly, 9 metal Mixed – Signal RF technology and a power supply of 1.2V are used for this design. For accuracy, best performance is obtained at the room temperature where the fastest operation is possible at cryogenic temperatures at the expense of precision. It has a DNL and INL of ±0.3LSB only at room temperature and ±0.45LSB at 120◦C. The DAC can operate up to 20MHz. The circuit dissipates only 0.43mW in full scale range at cryogenic temperatures where only 1.1mW at room. It occupies a chip area of only 0.015mm2.