  Within the ATTRACT FASTPIX project, a monolithic pixel sensor demonstrator
chip has been developed in a modified 180 nm CMOS imaging process technology,
targeting sub-nanosecond timing precision for single ionising particles. It
features a small collection electrode design on a 25 micrometers-thick
epitaxial layer and contains 32 mini matrices of 68 hexagonal pixels each, with
pixel pitches ranging from 8.66 to 20 micrometers. Four pixels are transmitting
an analog output signal and 64 are transmitting binary hit information. Various
design variations are explored, aiming at accelerating the charge collection
and making the timing of the charge collection more uniform over the pixel
area. Signal treatment of the analog waveforms, as well as reconstruction of
digital position, time and charge information, is carried out off-chip. This
contribution introduces the design of the sensor and readout system and
presents performance results for various pixel designs achieved in recent test
beam measurements with external tracking and timing reference detectors. A time
resolution below 150 ps is obtained at full efficiency for all pixel pitches.
