  Depleted monolithic CMOS active pixel sensors (DMAPS) have been developed in
order to demonstrate their suitability as pixel detectors in the outer layers
of a toroidal LHC apparatus inner tracker (ATLAS ITk) pixel detector in the
high-luminosity large hadron collider (HL-LHC). Two prototypes have been
fabricated using 150 nm CMOS technology on high resistivity (> 2 k$\Omega$
$cm^2$) wafers. The chip size is equivalent to that of the current ATLAS pixel
detector readout chip. One of the prototypes is used for detailed
characterization of the sensor and the analog readout of the DMAPS. The other
is a fully monolithic DMAPS including fast readout digital logic that handles
the required hit rate. In order to yield a strong homogeneous electric field
within the sensor volume, thinning of the wafer was tested. The prototypes were
irradiated with X-ray up to a total ionization dose (TID) of 50 Mrad and with
neutrons up to non-ionizing energy loss (NIEL) of $10^{15}$ $n_{eq}/cm^2$. The
analog readout circuitry maintained its performance after TID irradiation, and
the hit-efficiency at > $10^7$ noise occupancy was as high as 98.9 % after NIEL
irradiation.
