ST unveils e-fuse automotive smart switch for protection, power saving, and functional safety
STMicroelectronics’ VNF1248F automotive e-fuse MOSFET controller combines ST’s fast-acting, advanced e-fuse features for harness protection and enhanced flexibility, enabling power saving and advanced performance in automotive functional-safety systems. A new addition to the STi2Fuse family, the VNF1248F reacts within 100μs, which is faster than a conventional wire fuse and ensures flexible and robust protection to avoid fault propagation inside the vehicle
The VNF1248F integrates the new capacitive charging mode (CCM) functionality to ensure proper driving of large capacitive loads with high inrush current. In addition, an enhanced Standby-ON mode with current capability up to 600mA and current consumption lower than 75uA enhances the vehicle’s efficiency when in park mode, helping increase autonomy. An optional external supply pin for logic reduces power consumption by 0.4W in 48V systems and battery-undervoltage shutdown compatible with the automotive LV124 standard ensures system stability.
The chip facilitates reaching high safety-integrity levels (ASIL) in ISO 26262 functional-safety applications thanks comprehensive dedicated features like advanced fault detection and reaction, fail-safe mode and limp-home mode. There are also built-in self tests for automatic diagnosis and a dedicated pin for direct hardware control of the external MOSFET gate in case of a microcontroller fault
Suitable for 12V, 24V, and 48V boardnets, the VNF1248F handles power distribution in zonal vehicle electrical architectures and general fuse and relay replacement. Other uses include as an ECU main switch and active supply for always-on circuitry in parking mode.
Joining ST’s STi2Fuse family of smart switches for wire harness protection and dynamic power distribution, the VNF1248F has an SPI port to interact with a host microcontroller. Configuring the device using SPI saves conventional external programming components and allows flexible control of settings including hard short-circuit (HSC) latch-off, current-vs-time latch-off in fuse emulation, and MOSFET-desaturation shutdown. With non-volatile memory (NVM) also on-chip, the VNF1248F can additionally store an immutable default configuration to ensure consistent behavior in failsafe or locked states.
The associated EV-VNF1248F evaluation board, pre-assembled and ready to connect directly to the load, power supply, and microcontroller, simplifies integration of ST’s intelligent fuse protection into prototype circuitry. A software package, STSW-EV-VNF1248F, is also available and provides a graphical user interface and control firmware to configure and monitor the VNF1248F using an EV-SPC582B microcontroller board.
