  The Short Baseline Near Detector (SBND) is one of three liquid argon (LAr)
neutrino detectors sitting in the Booster Neutrino Beam (BNB) at Fermilab as
part of the Short Baseline Neutrino (SBN) program. The detector is in a
cryostat holding 260-ton of LAr and consists of four 2.5 m (L) $\times$ 4 m (W)
Anode Plane Assembles (APAs) and two Cathode Plane Assemblies (CPAs), which
leads to 11,264 Time Projection Chamber (TPC) readout channels and two separate
2 m long drift regions. As an enabling technology, Cold Electronics (CE)
developed for cryogenic temperature operation makes possible an optimum balance
among various design and performance requirements for such large sized
detectors. Brookhaven National Laboratory (BNL) has been leading the R&D and
implementation of the entire front-end CE system for LAr TPC readout in
collaboration with other SBND institutes. The front-end readout electronics
system includes the cold front-end electronics placed close to the wire
electrodes, which detects and digitizes the charge signal in LAr, as well as
the warm interface electronics placed on the signal feed-through flange outside
of the cryostat, which further organizes and transmits the digitized signal to
the DAQ system. An extensive study of electronics suitable for 77 K - 300 K,
including the custom designed front-end ASIC and commercial components, e.g.
ADC and FPGA, has been made to meet requirements such as low noise, low power
consumption, high reliability and long lifetime. Furthermore, an integral
design concept of APA, CE, feed-through, warm interface electronics with local
diagnostics, grounding and isolation rules has been practiced with vertical
slice test stands to make projection of the CE performance in the SBND
detector.
