  ALDO2 is a multi-function, adjustable, low dropout linear regulator designed
in onsemi I3T80 0.35~$\mu$m HV CMOS technology for use in HEP detectors that
adopt silicon photomultipliers (SiPMs). The chip features four independent
regulators, two low voltage channels (max 3.3 V) used to filter and stabilize
the power supply of front-end chips, and two HV channels (max 70 V),
specifically designed to provide the bias voltage to arrays of SiPMs. Each
regulator can be independently shut down and is protected for over-current and
over-temperature. The HV regulators also implement a circuit to monitor the
bias current of the SiPM arrays, allowing to perform I-V curves and thus to
fine-tune the working point of the SiPM arrays during the detector lifetime.
The chip adopts radiation hardening techniques and has been fully qualified up
to a TID of 20 Mrad, a 1-MeV-equivalent neutron fluence of $10^{15}$ cm$^{-2}$,
and with heavy ions up to 40 MeV cm$^2$ mg$^{-1}$ LET and $10^{10}$ cm$^{-2}$
cumulative fluence. The chip will be installed in two CMS detectors in the
HL-LHC phase, the Barrel Timing Detector (BTL) and the High Granularity
Calorimeter (HGCAL).
