Automotive high side switch controller incorporates fuse protection

Silicone fuses help simplify vehicle wiring harnesses and reduce weight by eliminating user-accessible fuse boxes and associated wiring and installation. Weight saving helps improve vehicle performance, including extended range and reduced CO emissions2 emissions.

Intelligent fuse protection can prevent automotive circuit board traces, connectors and wiring harnesses from overheating, often without impacting load transients such as inrush currents. Such requirements can ensure that the insulation of wires and PCBs is subject to a limited temperature and time budget, less than the specified reliability values.

Failure to adhere to these specified limits may lead to a conductive path being formed by charring through the organic insulating materials and the local hot spot may lead to sparking and ignition of a fire.

STi2Fuse is a new family of smart fuses from STMicroelectronics aimed at replacing standard fuse fuses in automotive power distribution systems. I am ST2t fuse—i2t represents the ampere squared second, also known as the melting point in a fuse, is a defining characteristic of the STi2Family of fuse products. It provides fast acting, resettable and reliable overcurrent protection. The STi2The Fuse family consists of two types of devices: an integrated solution for low/medium power ranges and a door controller for high power ranges.

STMicro’s exclusive eFuse technology includes intelligent circuit cutoff to protect circuit board traces, connectors, and wire harnesses from overheating. According to the company, these devices reduce component and production costs, while extending the range of electric vehicles (EVs) and reducing the vehicles carbon footprint. Device monitoring, control and digital interface capabilities help automotive systems comply with ISO 26262 and associated Safety Integrity Levels (SILs).

Power protection

The VNF1048F The Automotive High Side Switch Controller combines system protection and diagnostic functions with eFuse functionality for implementing an overcurrent protection mechanism. The control IC is interfaced to a host microcontroller via a 3.3 and 5V CMOS compatible SPI interface and provides system protection and diagnostics.

As the first in ST’s new STi2Family of fuses with integrated I2For protection, the VNF1048F is compatible with 12, 24, and 48 V automotive power subsystems. Its flexibility is well suited to the latest automotive zonal electronic/electrical architectures that improve efficiency and reliability while supporting increased electrification.

The controller has a serial peripheral interface (SPI) for a host microcontroller to configure and monitor system protection and diagnostics. These include undervoltage and overtemperature protection, thermal protection for the external high-side MOSFET, desaturation shutdown, and I2t fuse settings. Precision digital current sensing is built in. Analog-to-digital converters (ADCs) for monitoring temperature-sensing thermistor voltage, output voltage, and MOSFET drain-source voltage are also built into the device.

When the current in the load is pulse width modulated, the eFuse function calculates the root mean square of the current. The root mean square of the current is also calculated when the power switch is turned on/off during normal operation or after a switch is turned off due to a short circuit/overload. So if, for example, the circuit is interrupted due to an overload and after a while the circuit is activated again, the eFuse keeps the previous condition in memory.

The VNF1048FTR is currently in production and available in the 32L 5×5mm, 32-pin QFN package starting at $1.77 for orders of 1,000 pieces.

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