  MiniCACTUS is a monolithic sensor prototype optimised for timing measurement
of charged particles. It has been designed in a standard 150 nm CMOS process
without dedicated amplification layer. It is intended as a demonstrator chip
for future large scale timing detectors, like upgrades of timing detectors at
LHC, or future high energy physics detector projects. The sensor features an
active array of 2 x 4 diodes, analog and digital Front-Ends (FEs), a slow
control interface, and bias circuitry programmable through internal DACs. The
sensing element is a deep n-well/p-substrate diode. Thanks to the optimized
guard-rings surrounding the whole chip, it is possible to apply safely more
than 450 V on the high-resistivity substrate allowing fast charge collection.
The baseline pixel dimensions are 1.0 mm x 1.0 mm and 0.5 mm x 1.0 mm. The
analog FEs and the discriminators for each pixel are implemented outside the
pixel, at the column level. The power consumption is approximately 300
mW/cm$\mathbf {^2}$, which is compatible with cooling infrastructure available
at LHC experiments, and making integration of this concept viable in future
high energy physics experiments. After fabrication, the sensors have been
thinned to 100 $\mu$m, 200 $\mu$m and 300 $\mu$m total thickness and then
post-processed for backside biasing. The time resolution of several sensors
with different thicknesses has been measured in 3 test-beam campaigns using
high energy muons (Minimum Ionizing Particles) at CERN SPS in 2021 and 2022. A
resolution of 65.3 ps has been measured with on-chip FE and discriminator. This
paper will focus on the results of these test-beam campaigns.
