  The DESY II Test Beam Facility is a key infrastructure for modern high energy
physics detector development, providing particles with a small momentum spread
in a range from 1 to 6 GeV to user groups e.g. from the LHC experiments and
Belle II as well as generic detector R&D. Beam telescopes are provided in all
three test beam areas as precise tracking reference without time stamping, with
triggered readout and a readout time of > 115 $\mu$s. If the highest available
rates are used, multiple particles are traversing the telescopes within one
readout frame, thus creating ambiguities that cannot be resolved without
additional timing layers. Several upgrades are currently investigated and
tested: Firstly, a fast monolithic pixel sensor, the TelePix, to provide
precise track timing and triggering on a region of interest is proposed to
overcome this limitation. The TelePix is a 180 nm HV-CMOS sensor that has been
developed jointly by DESY, KIT and the University of Heidelberg and designed at
KIT. In this publication, the performance evaluation is presented: The
difference between two amplifier designs is evaluated. A high hit detection
efficiency of above 99.9 % combined with a time resolution of below 4 ns at
negligible pixel noise rates is determined. Finally, the digital hit output to
provide region of interest triggering is evaluated and shows a short absolute
delay with respect to a traditional trigger scintillator as well as an
excellent time resolution. Secondly, a fast LGAD plane has been proposed to
provide a time resolution of a few 10 ps, which is foreseen to drastically
improve the timing performance of the telescope. Time resolutions of below 70
ps have been determined in collaboration with the University of California,
Santa Barbara.
