  Depleted monolithic active pixel sensors (DMAPS), which exploit high voltage
and/or high resistivity add-ons of modern CMOS technologies to achieve
substantial depletion in the sensing volume, have proven to have high radiation
tolerance towards the requirements of ATLAS in the high-luminosity LHC era.
Depleted fully monolithic CMOS pixels with fast readout architectures are
currently being developed as promising candidates for the outer pixel layers of
the future ATLAS Inner Tracker, which will be installed during the phase II
upgrade of ATLAS around year 2025. In this work, two DMAPS prototype designs,
named LF-MonoPix and TJ-MonoPix, are presented. LF-MonoPix was designed and
fabricated in the LFoundry 150~nm CMOS technology, and TJ-MonoPix has been
designed in the TowerJazz 180~nm CMOS technology. Both chips employ the same
readout architecture, i.e. the column drain architecture, whereas different
sensor implementation concepts are pursued. The design of the two prototypes
will be described. First measurement results for LF-MonoPix will also be shown.
