  The next generation of space-based mm-wave telescopes, such as JAXA's
LiteBIRD mission, require focal planes with thousands of detectors in order to
achieve their science goals. Digital frequency-domain multiplexing (dfmux)
techniques allow detector counts to scale without a linear growth in wire
harnessing, sub-Kelvin refrigerator loads, and other scaling problems. In this
paper, we introduce Technology Readiness Level 5 (TRL5) electronics suitable
for biasing and readout of LiteBIRD's Transition Edge Sensor (TES) bolometers
using dfmux techniques. These electronics sit between the spacecraft's payload
computer and the cryogenic focal plane, and provide detector biasing, tuning,
and readout interfaces between these detectors and the spacecraft's on-board
storage. We describe the overall architecture of the electronics, including
functional decomposition into modules, the numerology and interconnection of
these modules, and their internal and external interfaces. We describe
performance measurements to date, including power consumption, thermal
performance, and mass, volume, and reliability estimates. This paper is a
companion piece to a description of the electronics' on-board
Field-Programmable Gate Array (FPGA) firmware.
