ATLASPix3 serial powering and multi-chip module studies for future HV-CMOS tracker

High voltage CMOS pixel sensors are proposed in many future particle physics experiments such as the HL-LHC upgrades and future circular colliders. The ATLASPix3 chip consists of 49104 pixels of dimension 50 μm × 150 μm, realised in 180 nm HVCMOS technology. It is the first full reticle size monolithic HVCMOS sensor suitable for construction of multi-chip modules and supporting serial powering through Shunt-Low-Dropout regulators. The readout architecture supports both triggered and triggerless readout with zero-suppression. With the ability to be operated in a multi-chip setting, a 4-layer telescope made with ATLASPix3 was developed, using a readout system made at KIT. To demonstrate the multi-chip capability and for its characterisation, a beam test was conducted at DESY using 3–6 GeV positron beams with the chips operated in triggerless readout mode with zero-suppression. Detailed electrical characterisations of the regulators are presented as well as multi-chip (quad module) readout and serial powering prototyping.