The Tile Calorimeter (TileCal) is the hadronic calorimeter covering the central region of the
ATLAS experiment. The High-Luminosity phase of LHC, delivering five times the LHC nominal
instantaneous luminosity, is expected to start in 2029. TileCal will require new electronics to meet
the requirements of a 1 MHz trigger, higher ambient radiation, and to ensure better performance
under high pile-up conditions. Both the on- and off-detector TileCal electronics will be replaced
during the shutdown of 2026-2028. Approximately 10% of the PMTs, those reading out the most
exposed cells, will be replaced. PMT signals from every TileCal cell will be digitized and sent
directly to the back-end electronics, where the signals are reconstructed, stored, and sent to the first
level of trigger at a rate of 40MHz. This will provide better precision of the calorimeter signals
used by the trigger system and will allow the development of more complex trigger algorithms.
The modular front-end electronics feature radiation-tolerant components and redundant design to
minimize single points of failure. The timing, control and communication interface with the off
detector electronics is implemented with modern Field Programmable Gate Arrays (FPGAs) and
high speed fibre optic links running up to 9.6 Gb/s. The TileCal upgrade program has included
extensive R&D and test beam studies. A Demonstrator module equipped with the new electronics
but with reverse compatibility with the existing readout system was inserted in ATLAS in August
2019 for testing in actual detector conditions. The status of the various components and the results
of test-beam campaigns with the electronics prototypes will be discussed.