Development of binary readout CMOS monolithic sensors for MIP tracking

Recently, CMOS monolithic active pixels sensors (MAPS) have become strong candidates for pixel detectors used in high energy physics experiments. A very good spatial resolution can be obtained with these detectors (lower than 5 microns). A recent fast MAPS chip, designed on AMS CMOS 0.35 mum Opto process and called MIMOSA16 (HiMAPS2), was submitted to foundry in June 2006. The pixel array is addressed row-wise. The chip is a 128 times 32 pixels array where 8 columns have analog test outputs and 24 have their outputs connected to offset compensated discriminator stages. The array is divided in four blocks of pixels with different conversion factors and is controlled by a serially programmable sequencer. Discriminators have a common adjustable threshold. The sequencer operates as a pattern generator which delivers control signals both to the pixels and to the column-level discriminators. This chip is the basis of the final sensor of the EUDET-JRA1 beam telescope which will be installed at DESY in 2009. In this paper, laboratory tests results using a ⁵⁵Fe source together with beam tests results made at CERN using minimum ionizing particles (MIPs) are presented.