When designing subsystems for the automotive market, two overriding concerns are high reliability and minimum power, the latter becoming increasingly more important as a vehicle’s battery (or batteries for electric vehicles) must power more subsystems with each new generation of car. In general, the environments and operating conditions for OTP memory in automotive and industrial applications are harsher than those found for consumer products and require OTP technology that can be reliably and securely deployed in high temperature and high voltage environments. “Under the hood” subsystems (AEC-Q100 Grade 0) must be able to operate at temperatures as high as 150°C., since size restrictions and wiring cost mean ECUs are mounted close to the engine or to transmission components that operate at elevated temperatures. Finally, some electronic subsystems must operate at voltages higher than those found in consumer and mobile products to deal with a car’s battery system.
The number of automotive sensors in a single vehicle has been steadily rising over time. Each new automobile has 60-100 sensors on-board measuring a very broad range of parameters, including temperature, humidity, light, pressure, fluid levels, positioning, engine combustion/detonation, acceleration, speed, lamp status, oxygen flow and compass direction (geomagnetic). The type of sensor a vehicle uses for a specific application depends on the parameter being measured and a single car will use several different types.
All sensing elements have nonlinearities that include an intrinsic nonlinearity over sensing range along with offset and sensitivity nonlinearity variations over temperature. Variations in component and circuit characteristics along with chip processing and packaging operations result in deviations of analog circuits and sensors from their target specifications. To optimize the performance of the systems in which these components are placed, it is necessary to “trim” interface circuitry to match a specific analog circuit or sensor. A trimming operation, often accomplished with OTP memory, compensates for variations in the analog circuits and sensors due to manufacturing variances of these components.
Automotive electronics subsystems are used in engine electronics, transmission electronics, chassis electronics, active safety systems, driver assistance systems, passenger comfort and infotainment systems.