Reliable and safe vehicle USB power supply

With the E522.43 IC, Elmos is presenting a USB-2.0 compatible power supply with comprehensive protection functions for use in vehicles. Thanks to the extensive pin configuration options and automatic detection as well as dedicated BC1.2 charging ports and distance of the connected USB device, this component is particularly well suited for standalone applications without an external microcontroller. The integrated circuit supports all USB charging downstream loads in accordance with the "Battery Charging Specification Revision 1.2" and also emulates the currently known specific USB chargers. A current dependent increase in the BUS voltage (negative resistance) allows for an optimal charging process even for large currents with wire losses.

System setup is performed entirely via three configuration pins, each with a resistance divider for the internal power supply. Any combination of USB port, switching frequency, overcurrent handling and/or corresponding limit values as well as current-dependent BUS voltage increases can be configured. Various mechanisms for detection of resistor encoding errors (such as a parity check) prevent activation of the IC with characteristics which could threaten the system in the event of resistance changes or malfunctions.

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

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 via the interrupt output and many other specific protection settings.

The E522.43 is also fully qualified according to AEC-Q-100 and is supplied in a thermally efficient 20 pin QFN housing for ambient temperatures of up to 105°C.

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