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This paper presents the first flash Analog-to-Digital Converter (ADC) in standard CMOS technology that functions from 300 K (room temperature) down to 4.2 K. It has been designed to operate in cryogenic sensor systems as they are cooled from room temperature to their final cryogenic operating temperature. In order to preserve the circuit's performance over this wide temperature range, even in the presence of temperature-induced transistor anomalies, dedicated architecture and switching schemes are employed. SPICE models for adequate circuit simulation at 4.2 K have been extracted. A first prototype of the chosen architecture, an 8-bit ADC in a standard 0.7 mum CMOS technology, achieves a differential nonlinearity (DNL) of 0.5 LSB at room temperature and 1 LSB at 4.2 K at a sampling frequency of 12.5 kHz.
Date of Publication: July 2009