ASIC provides comprehensive functions for automotive airbag system
ASIC provides comprehensive functions for automotive airbag system
Keywords Automotive,Safety
Allegro MicroSystems has developed an application-specific integrated circuit (ASIC) which provides all the monitoring and control functions required for a four-loop automotive airbag system.
The new QuADDS™ 2487 incorporates a password protected 16-bit serial interface for command and diagnostic status reporting. Buck and boost power converters generate 30V and 5V, respectively, and four current-controlled output drivers are provided for the pyrotechnic "squibs" which provide the air bag inflation and seat-belt retention functions (Plate 3).
Two additional output drivers, which can operate as high-side or low-side drivers, are included for bulb or relay control, and a further low-side driver is intended to trigger an alarm system such as a chime module.
The power-conversion scheme uses the boost converter, operating directly from the battery source, to charge an output energy storage capacitor and to provide a source for the 5V buck converter. This scheme allows operation at supply levels of below 5V.
Plate 3 The QuADDS 2487 automotive airbag control IC from Allegro MicroSystems
Both converters use on-chip switching transistors with an internal oscillator, using an inexpensive ceramic resonator, to achieve tightly controlled switching frequency as well as providing a timebase for the on-chip watchdog function.
The device provides a full set of diagnostic functions for monitoring system faults such as output short-circuits to supply and ground, detection of output boost converter level,and precise squib resistance measurement.
The system designer can utilise internally preset fault levels, reported via the SPI bus (digital mode),or can override them via the multiplexer interface to the system microcontroller's analogue/digital converter circuitry (analogue mode).
An analogue multiplexer provides interface capability for the diagnostic functions, as well as for other system components such as accelerometers and occupant detection sensors.
For further information contact Allegro MicroSystems Europe Ltd, Balfour House, Churchfield Road,Walton-on-Thames, Surrey KT12 2TD, UK. Web site: http://www.allegromicro.com
