Large Area SiPM Readout and Signal Processing for nEXO*

nEXO is a proposed 5 tonne liquid xenon time projection chamber to search for neutrinoless double beta decay of ¹³⁶Xe. The central detector will implement several improvements over the previous generation experiment, EXO-200. One such improvement is the usage of silicon photomultipliers (SiPMs) instead of avalanche photodiodes (APDs) as scintillation light detectors. In this presentation, I will discuss the electronics readout of large area FBK UV sensitive SiPMs at liquid xenon temperatures, the digital processing of SiPM waveforms, and some of the challenges that are common to large area readout. We tested the SiPMs in both parallel and series configurations and demonstrated that up to 6 cm² of SiPMs can be read out by a single front end channel  while maintaining nEXO requirements specified in the pre-conceptual report.