CMOS Schmitt – Inverter-Based Internal Reference Comparator Array for High Temperature Flash ADC

ABSTRACT

Localized data conversions for sensors placed under harsh environmental conditions often require Analog to Digital Converters (ADC) capable of working under wide operating temperature range. Even though the fastest analog to digital converter, flash ADC is omitted from the high temperature regime due to the requirements of reference voltage source, reference voltage divider and a comparator array capable of providing stable operation under wide operating temperatures. A CMOS Schmitt inverter-based internal reference comparator array for flash ADC which is efficient in terms of area and power consumption, capable of working under wide temperature range is presented in this paper. The proposed idea replaces the reference voltage source, resistive reference voltage divider and differential comparator array of a conventional flash ADC by an array of suitably sized Schmitt inverters. The circuit was simulated for static and dynamic characteristics with gpdk 180 nm library using cadence virtuoso simulation suite. The voltage transfer characteristic curve (VTC) of the proposed comparator array was found invariable when a temperature sweep in the range of −40 to 170 degree Celsius was performed. Each of the comparator in the proposed array consumes a silicon area of 40.68 ${\mathrm{u}\mathrm{m}}^2$ and the average dynamic power consumption per cycle is estimated as 103.1 uW.

KEYWORDS:

• Threshold inverter quantizer
• TIQ
• CMOS Schmitt inverter
• Thermal reliability
• Inverter threshold compensation
• High temperature circuit design
• Flash ADC

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

George M. Joseph

George M Joseph graduated in electronics and communication engineering from Bharathidasan University, Trichy, India, in 1998 and received post graduate degree in electronic design technology from National Institute of Technology Calicut, Kerala, India, in 2007. Since 2001, he has been a member of the faculty of the Department of Electronics and Communication Engineering, Sree Chitra Thirunal College of Engineering, Thiruvananthapuram, Kerala. Presently, he is doing research in the area of design and analysis of high performance data converters, under University of Kerala, India. He is a Member of IEEE. His areas of interests are analog and mixed signal design, low power electronics, data converters and high speed circuit design.

T. A. Shahul Hameed

Shahul Hameed T A received BTech (Electronics and Communication Engineering) from University of Kerala, India, MTech (Microelectronics and VLSI Design) from IIT Kharagpur, India and PhD (Electronics and Communication Engineering) from University of Kerala, India. He has 20 years of teaching experience and 8 years of industrial experience. He is currently the head of the Institution, TKM College of Engineering, Kollam, Kerala, India and also a professor in Electronics and Communication Engineering Department. He has authored more than twenty international journal and conference papers. His areas of interests are organic devices, quantum devices and device modelling. Email: [email protected]