A 130nm ASIC prototype for the NA62 Gigatracker readout

Abstract

Abstract One of the most challenging detectors of the NA62 experiment is the silicon tracker, called Gigatracker. It consists of three hybrid silicon pixel stations, each one covering an area of 27 mm×60 mm. While the maximum pixel size is fairly large, 300 μ m × 300 μ m the system has to sustain a very high particle rate, 1.5 MHz/mm 2 , which corresponds to 800 MHz for each station. To obtain an efficient tracking with such a high rate the required track timing resolution is 150 ps (rms). Therefore the front-end ASIC should provide for each pixel a 200 ps time measurement capability, thus leading to the requirement of time walk compensation and very compact TDCs. Moreover, Single Event Upset protection has to be implemented in order to protect the digital circuitry. An ASIC prototype has been realized in CMOS 130 nm technology, containing three pixel columns. The chip performs the time walk compensation by a Constant Fraction Discriminator circuit, while the time measurement is performed by a Time to Amplitude Converter based TDC, both of them implemented on each pixel cell. The End of Column circuit containing only digital logic is responsible for the data readout from the pixel cell. The whole chip works with a system clock of 160 MHz and the digital logic is SEU protected by the use of Hamming codes. The detailed architecture of the ASIC prototype and test results are presented.