  The front-end electronics of silicon detectors are typically designed to
ensure optimal noise performance for the expected input charge. A combination
of preamplifiers and shaper circuits result in a nontrivial response of the
front-end to injected charge, and the magnitude of the response may be sizeable
in readout windows subsequent to that in which the charge was initially
injected. The modulation of the discriminator threshold due to the
superposition of the front-end response across multiple readout windows is
coined "threshold bounce".
  In this paper, we report a measurement of threshold bounce using silicon
modules built for the Phase-II Upgrade of the ATLAS detector at the Large
Hadron Collider. These modules utilize ATLAS Binary Chips for their hit
readout. The measurement was performed using a micro-focused 15 keV photon beam
at the Diamond Light Source synchrotron. The effect of the choice of photon
flux and discriminator threshold on the magnitude of the threshold bounce is
studied. A Monte Carlo simulation which accounts for the front-end behaviour of
the silicon modules is developed, and its predicted hit efficiency is found to
be in good agreement with the measured hit efficiency.
