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By Giusy Gambino, STMicroelectronics Automotive power distribution is becoming an active part of the vehicle’s electrical and electronic system rather than a passive switching layer. In conventional, hybrid, and battery electric vehicles, each supply channel may need to maintain retained functions, recover rapidly at wake up, protect wiring and connectors, and provide diagnostic information within increasingly distributed E/E architectures.

The design challenges extend beyond selecting a switch with sufficient current rating. The
architecture must combine low standby consumption, controlled activation, predictable
thermal behavior, fault containment, and bounded energy release across the operating
envelope.
During extended parking, selected loads may remain powered for remote diagnostics, over-the-
air updates, security, telemetry, or keyless entry, while their combined current stays within
the battery budget. At wake up, the same channel must support higher current without
excessive voltage drop or disturbance of downstream loads.
The standby to active transition also challenges protection. Capacitive inrush and a short
circuit can produce similar initial current signatures, while inductive loads can generate fast
transients. Protection must tolerate valid events, interrupt sustained overloads before
harness damage, and remain active during MCU reset, communication delay, undervoltage,
or invalid configuration.