LED Technology
interface. It is ASIL compliant (ISO 26262) and supports system integration up to ASIL B, meeting the functional safety requirements of EV charging ports.
With its smart microcontroller unit (MCU) plus embedded flash memory, the MLX81118 offers flexible system design and convenient function updates. The primary role of the IC is to function as an LED driver, offering programmable current sources with up to 60mA per channel low side (max 1A LED current) and a 16-bit PWM (500 Hz) for brightness control. The system provides support for static lighting and basic LED animation. Additionally, each LED is fully diagnosable, and its temperature can be determined by measuring the LED threshold voltage (refer to Figure 2).
Where the functionality differentiates from existing offerings is in the product’s versatility. It offers 24 channels capable of driving an RGB and/or single-colour LED – more than most typical automotive LED drivers designed for charging ports. Additionally, these channels can also be configured as general-purpose input/output (GPIO) channels. The GPIO functionality includes features such as 5V supply output at 20mA, support for SPI/I2C communication, external wake-up capability, and the ability to configure the GPIOs with the integrated analog-to-digital converter (ADC). The presence of this facility permits a more extensive range of applications with advanced functionality and localized control capabilities, surpassing the conventional functionality of an LED IC.
Developing smarter charging ports Within a vehicle, Melexis’ MLX81118’s flexibility can be leveraged by engineers to build smarter charging ports, without significantly expanding the Bill of Materials (BoM) component count.
In a charging point installation, the integrated 10-bit ADC can be configured to the GPIOs, for example, to measure the temperature of sensors at one or more of the high-voltage connectors of the charge port. In a functional safety environment, it is imperative to be aware of the temperature of the charging connectors. Furthermore, the IC driver is equipped with an internal temperature sensor to complement any external measurement and offers precise information regarding the ambient temperature of the charge port. In this configuration, the MLX81118 can precisely monitor information for external temperature sensors and relay this information. For example, in the event of an over-temperature error, the IC’s smart programming can be utilized to alert the
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Figure 3: Melexis MLX81118 charging port lighting, the example circuit with temperature sensors and flap monitoring (Source: Melexis)
driver of excessive heat in the port, potentially through the use of red flashing LEDs in the vicinity. At the same time, this information can be output back to other wider components and controllers via the LIN interface, or GPIO channels configured as an SPI or I2C interface. Beyond temperature-related functionality, the flexibility of the MLX81118 can aid designs to improve other areas of the charging ports’ safety as well as the end user’s experience (Figure 3).
A convenient approach for monitoring the open or closed status of the charge flap is the incorporation of a Hall sensor with a magnet. For example, Melexis’ MLX92292 Hall effect latch and switch sensor could be used. The Hall sensor IC’s output connects to the GPIOs of the MLX81118, allowing the flap position to be monitored by a vehicle body domain controller (BDC) through the LED driver’s LIN interface. This smart integration can help to reduce the number of connections to the vehicle’s BDCs, as well as allow changes in
the flap position to trigger the LEDs directly. This smart integration and direct connection between the flap position and LED driver can also be used to implement functionality, which elevates the end-user experience. For example, in dark conditions, the MLX81118 could be configured so that once the flap is opened and a circuit change is detected due to the MLX92292 switching state, the controlled LEDs around the charging port illuminate. Equally, designers have the option to incorporate additional intelligent functionalities, such as flashing the port LEDs in a distinguishable manner when the charging port flap remains open after disconnecting the charger, thus minimizing the likelihood of damage while driving. Another possibility is to convey the charging status through varying numbers of illuminated LEDs or colour changes. Compared to conventional installations needed to implement such functionality,
with the MLX81118, the logic and control is all managed at the charging point components, reducing the processing load on central or zonal vehicle control systems.
Conclusion
Automotive designers are always looking for intelligent solutions that can make localised decisions and perform safety- critical tasks without significantly increasing component count or processing load. LEDs have also become an important aspect of automotive design, allowing OEMs to make their models visually distinct and relay important information to the user. The MLX81118 is in line with these trends, offering an innovative new approach to LED installations in EV charging ports and beyond, with the solution’s flexibility also beneficial to other areas of vehicle design and wider markets.
https://www.melexis.com/ Components in Electronics February 2024 43
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