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IC supports USB power supply for vehicles

23 Sep 2014

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Elmos introduced E522.41, an integrated circuit for a USB-2.0 compatible power supply with comprehensive protection functions for use in vehicles.

The IC supports all USB charging downstream loads in accordance with the "Battery Charging Specification Revision 1.2" and emulates the currently known specific USB chargers. In addition, a configurable encoding network is available for future custom solutions. A current dependent increase in the BUS voltage (negative resistance) allows for an optimal charging process even for large currents with wire losses.

An I2C interface allows for real-time system setup and diagnostics via an external microcontroller. The momentary USB voltage and application current values in particular can be read in order to implement effective monitoring. Three different I2C bus system addresses are decoded by the ADR pin. As an alternative for low cost applications, the E522.41 can also be operated in a variety of stand-alone configurations.

The internal switched mode power supply (SMPS) efficiently provides a USB supply voltage of 5V plus-minus 3 per cent at a maximum output current of 2.5A. The allowable input voltage range is between 6V and 32V with brief peaks of up to 42V. The switching frequency can be programmed to the following four centre frequencies: 250kHz, 500kHz, 1MHz, or 2MHz. In master-slave configurations with other devices, these can also be synchronised by an additional plus-minus 25 per cent through an internal PLL (Frequency Parking). The EMC behaviour can be improved considerably through activation of the light load detection and spread spectrum modes.

Particular attention during development was placed on the robustness requirements in automotive environments. This is apparent in light of the following features, among others: ISO7637 pulse immunity at the input, short circuit protection for the USB interface (BUS and/or data lines) to VBAT/GND, over and under voltage monitoring of the USB supply, monitoring of the internal reference voltage and overheating protection, signalling of fault states or warnings via the interrupt output and many other specific protection settings.

The E522.41 is also fully qualified according to AEC-Q-100 and is supplied in a thermally efficient 20pin QFN housing for ambient temperatures of up to 105°C.

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