STs VNF1248F Automotive E-Fuse Controller Targeting 48V Power Distribution

STMicroelectronics has recently introduced the VNF1248F automotive e-fuse controller, expanding its STi²Fuse family. This innovative device is designed to protect wire harnesses and manage power distribution in 12 V, 24 V, and 48 V boardnets. The VNF1248F offers fast electronic protection and flexible configuration to support zonal architectures and relay replacement in modern vehicles.

For engineers and designers in the automotive industry, the emergence of 48 V boardnets and electrified powertrains is driving the need for solid-state protection solutions. The VNF1248F addresses this demand by providing tunable, monitorable, and integrable electronic protection, moving away from traditional fixed wire fuses.

Enhanced Protection for 48 V Architectures

ST highlights that the VNF1248F boasts a rapid reaction time of 100 µs, outperforming conventional wire fuses. This quick response can help contain fault propagation in the harness during short circuits or overloads. Additionally, the device features a capacitive charging mode (CCM) to manage high inrush currents from large capacitive loads commonly found in 48 V zones.

In scenarios where the vehicle is parked or in low-power modes, the controller offers an enhanced Standby-ON mode with a current capability of up to 600 mA while maintaining low consumption below 75 µA. This feature enables support for always-on loads without significantly draining the battery. An optional external logic-supply pin can reduce power consumption by approximately 0.4 W in 48 V systems, and an LV124-compliant battery undervoltage shutdown function ensures consistent system behavior during supply dips.

The VNF1248F is positioned by ST for various applications including power distribution in zonal vehicle electrical architectures, fuse and relay replacement, ECU main switching, and powering "always-on" circuitry. The device comes in a compact 5 mm x 5 mm QFN-32 package and is currently in production, with indicative pricing starting at $2.63 for 1,000-piece quantities.

Functional Safety, Configurability, and Tools

Designed to align with ISO 26262 functional-safety standards, the VNF1248F integrates fault-detection and reaction mechanisms such as fail-safe and limp-home modes. The device incorporates dedicated diagnostics, built-in self-tests, and a hardware pin for direct control of the external MOSFET gate in case of microcontroller failure, aiding in achieving higher ASIL targets in critical control domains.

Configuration of the VNF1248F is facilitated through an SPI interface to a host microcontroller, allowing software-based adjustment of parameters like hard short-circuit latch-off behavior, current-versus-time fuse emulation, and MOSFET desaturation shutdown. The on-chip non-volatile memory stores an immutable default configuration, ensuring the e-fuse can revert to a predefined state in failsafe or locked conditions without relying on software initialization.

For evaluation purposes, ST offers the EV-VNF1248F board, which comes pre-assembled for easy connection to load, supply, and microcontroller. Additionally, the STSW-EV-VNF1248F software package provides a graphical user interface and firmware running on an EV-SPC582B board to configure and monitor the VNF1248F. This comprehensive toolset can streamline the assessment of solid-state fuse strategies in 48 V and multi-voltage automotive platforms, potentially accelerating development for engineering teams.