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How Current-Limiting Power Switches Improve Reliability for Automotive Electronics

By: Wonsoo Moon, System Engineering Manager


Today’s vehicles are adding more and more electronic components, increasing the overall vehicle cost and exacerbating the growing challenge of protecting components against electrical damage while maintaining reliability.

All devices in a car, including all of the electronic control units (ECUs), draw their power from the car’s battery—making them susceptible to spikes or surges in current, including surges during turn on and off. This susceptibility creates the need to provide protections against electrical damage.

Another similar application is the protection of a vehicle’s USB ports to ensure that the power supplied meets the requirements of the USB standard, while protecting the consumer devices plugged into these ports.

Modern cars have an increasing number of USB ports distributed around the interior. They are required, by the USB specification, to deliver a nominal 5V DC, with the USB 2.0 standard supporting currents of up to 500mA, for 2.5W power.

USB 3.0, USB Type-C® (or USB-C®), and more recent variants provide higher-power versions as well. While USB-C ports are still a rarity in today’s cars, IHS Markit estimates that more than a quarter of vehicles will have them by 2025.


Protecting Against Power Problems

How should we meet the challenge of protecting USB ports and ECUs?

Diodes Incorporated has addressed this with the DIODES™ AP22653Q, an automotive-compliant and adjustable current-limiting power switch. With a tight accuracy margin of ±7% at high current levels, the AP22653Q limits the current to a safe level as it passes. The device’s current-limit threshold can be easily set with standard value external resistors to anywhere between 125mA and 1735mA (peak)—while enabling it to provide a continuous output of up to 1.5A.

To mitigate the effect of surges during turn on/off, the AP22653Q has well-controlled rise and fall times. In addition, its 5μs short-circuit response helps prevent unnecessary system shutdown or restart, improving reliability. The reverse-current protection integrated into the device safeguards against reverse currents when peripherals are being externally powered. Also included in the device are overtemperature protection and undervoltage lockout features.

As expected of a part targeting the automotive market, the AP22653Q power switch is qualified to AEC-Q100 Grade 1. It has an operational temperature range of -40°C to 125°C and is supplied in a space-saving SOT26 package, making it possible for use in tight spaces in the vehicle.

Another important characteristic of the AP22653Q is its low on-resistance of 55mΩ (typical). This significantly reduces power loss and voltage drop at high-load currents, and limits the power dissipation within the device—thus improving reliability as less heat is emitted in operation.

With the increasing complexity of vehicle electronics, efficient power switches such as the AP22653Q are becoming a must-have to protect against overcurrent and power spikes.


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