What is an automotive eFuse? Differences from fuses and I²t wire protection | Infineon PROFET™ Wire Guard

In automotive power supply design, where the trend towards EVs and zone architectures is progressing, the increasing length of wiring, the rise in short-circuit energy, and the sophistication of diagnostic requirements mean that conventional fuses are increasingly unable to meet the demands in terms of interruption accuracy, reproducibility, and diagnostic capabilities.

This article explains, from an engineer 's perspective, the fundamental technical differences between automotive eFuses and fuses, the concept of wire thermal protection based on I²t, and the specific design benefits that Infineon's PROFET ™ Wire Guard brings to automotive power supply designs.

What is eFuse?

eFuse (Electronic Fuse) is a device that uses semiconductor switches and protection logic to detect abnormalities such as overcurrent, short circuits, and overheating (within the IC), and controls the output to protect loads and wiring. Unlike conventional fuses, which provide passive protection through "blown-out," eFuse features functions such as current monitoring, current limiting (method varies depending on the product), short-circuit interruption, re-closing (retry), and diagnostic output, making it easier to design and understand the interruption conditions and status.

Particularly in the automotive sector, the increasing complexity of power distribution due to zone architectures and the shift to electric vehicles, coupled with the growing demand for diagnostics and fault detection from a functional safety perspective, and the need for remote diagnostics and improved serviceability, are driving the shift towards power distribution protection using eFuses.

The difference between a fuse and an eFuse

Conventional fuses are passive components that protect circuits by physically melting when an overcurrent flows through them, due to the heat generated by their internal element. While they have the advantages of a simple structure and low cost, they need to be replaced once they melt, and it is not possible to precisely control the current or energy until the circuit is interrupted.

On the other hand, eFuse (electronic fuse) uses semiconductor devices to monitor current and actively limits current or performs rapid interruption when it detects overcurrent or short circuits. Its major features include the ability to be reset, control current values and energy (I²t), and output diagnostic information.

item	Conventional fuses	eFuse
Protection method	Thermal cutting	Electronic control
Response time	ms order	μs order
Reset	✖	✔
diagnosis	✖	✔
Changing the overcurrent threshold	✖	✔
Changes to ^I2t characteristics	✖	✔
merit	low cost Simple configuration Years of experience	High-speed protection Diagnostic and reset function Energy control is possible.
Demerit	Replacement is needed Diagnosis impossible Wire optimization is difficult.	Circuit design is required. The cost of the parts is on the higher side.

As summarized in the simple comparison table, the essential difference is that fuses provide passive protection by "melting" to protect, while eFuses provide active protection by "monitoring and controlling."

Infineon is leveraging its long-standing expertise in IPD development and track record to expand its product lineup with the eFuse PROFET™ Wire Guard series.

Features of PROFET™ Wire Guard

PROFET™ Wire Guard is an intelligent eFuse that combines I²t-based wire protection with adjustable overcurrent protection for high-precision protection of wire harnesses.

1. I²t wire protection function selectable with external resistor.

This device features six selectable I²t protection curves via external resistors, enabling protection control that simulates thermal characteristics based on wire diameter. This allows for accurate monitoring of thermal stress applied to the wire and automatically shuts off the switch when a preset critical threshold is reached.

Furthermore, because it can be reactivated in response to a decrease in wire temperature, it eliminates the need for physical replacement like a fuse.

In addition, since the protection function operates in hardware, it can be used without the control of a microcontroller (µC), contributing to reduced development and verification workload, as well as lighter and more cost-effective wire harnesses.

2. Automatic IDLE mode with low power consumption

PROFET™ Wire Guard automatically switches to IDLE mode when the load current meets certain conditions, reducing current consumption to approximately 50µA (typical). Even in this mode, the output remains active, continuing power supply and protection. When the load current increases, it automatically returns to normal mode and notifies the microcontroller of its status via the IDL pin, making it suitable for low-power operation such as parking.

3. Advanced monitoring through sequential diagnostics

The sequential diagnostic function allows you to read the status of various devices through a single analog current sense output.

It can acquire information such as current values, fault conditions, I²t settings and status, and overcurrent settings, supporting advanced power management and system monitoring, thereby supporting power distribution optimization and safety design in fail-operational architectures.

4. Adjustable overcurrent protection via external resistor.

The overcurrent threshold (OCT) can be set using an external resistor and adjusted from the nominal current to the maximum overcurrent level. This allows for flexible overcurrent protection design tailored to system requirements. Furthermore, it protects the power system from high fault currents through rapid fault detection and quick fault isolation from the power line.

5. Capacitive Load Switching (CLS) function

Capacitive Load Switching (CLS) mode allows for safe startup of loads with large input capacitors without triggering overcurrent protection due to inrush current. Because it can charge the capacitor while suppressing inrush current, it reduces stress on the system power supply and eliminates the need for an external pre-charge circuit, contributing to a reduction in component count and PCB area.

Product lineup

The PROFET™ Wire Guard series offers six different product lines. By standardizing the packaging of some products, you can consider upgrading or downgrading the specifications while maintaining pin compatibility.

Products	IL Nominal Current @Ta=85°C [A]	I²t Protection (A)	RDS(on)	Infineon Package name
BTG70008A-1ESW	36.5A	5 - 20A	0.9mΩ	PG-TSDSO-24
BTG70013A-1ESW	26.6A	5 - 20A	1.5mΩ	PG-TSDSO-24
BTG70020A-1ESW	21.5A	14.1 - 23.9A	2.2mΩ	PG-TSDSO-24
BTG7003A-1EPW	15.7A	10.3 - 17.4A	3.6mΩ	PG-TSDSO-14
BTG7007A-1EPW	10.3A	6.7 - 11.4A	8.0mΩ	PG-TSDSO-14
BTG7016A-1EPW	6.8A	4.4 - 7.5A	18.0mΩ	PG-TSDSO-14

Development environment

Infineonoffers evaluation boards that allow you to quickly verify the performance of each product.

Motherboard

Daughterboard

μIO-Stick

Summary

While conventional fuses are passive components selected based on "current value," PROFET™ Wire Guard is an active control device that protects based on "energy." In modern vehicles, where zone ECUs, EVs, and high functionality are advancing, protective devices also need to evolve.

As zone architectures, EV adoption, and functional safety requirements increase, power distribution protection also needs to evolve. PROFET™ Wire Guard is a next-generation wire protection solution that simultaneously achieves weight reduction, advanced diagnostics, simplified safety design, and improved serviceability. Please consider PROFET™ Wire Guard.

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Infineon's automotive lineup

Among Infineon's wide-ranging portfolio of products, we have compiled a lineup of only automotive-grade products that have been certified to AEC-Q100/AEC-Q101.
We have many products that can be considered for a variety of applications, including microcontrollers, power semiconductors, memory, and sensors, so please take a look.