An application-specific integrated circuit (ASIC) that combines analog and digital circuits distinguishes between an adult and a rear-facing infant seat on the passenger side of vehicles. AMS (formerly austriamicrosystems), Raleigh, N.C., developed the ASIC as the primary controller for Tokyo-Based Takata Corp.’s CS3 (Child Seat Suppression System). CS3 prevents the passenger air bag from deploying if a child seat is present.
Current passenger air-bag shutoff devices use a weight switch to detect someone sitting in the seat. However, the weight of a child in a safety seat may be enough to trigger the sensor, letting the air bag deploy in a crash. The explosively inflating air bag can severely injure children in safety seats.
In contrast, CS3 uses an electric field that measures the capacitive coupling between the sensing electrode in the seat, the occupant, and vehicle ground. The mass and position of the seat occupant affects the magnitude of the signal detected, clearly distinguishing between children and adults.
The AMS’s ASIC works despite high electromagnetic disturbances such as the those generated when operating mobile phones in a car.