Another unique feature of the sensor interface is its ability to enable programmable clamping at low- and high-output levels. Enabling clamping ensures the sensor’s ability to detect minimum and maximum output levels and the ability of the ECU to check whether the sensor’s output is within an acceptable range.
Furthermore, the MLX90320 sensor interface in our example integrates fault detection, making it suitable for a range of automotive applications. Capable of detecting internal and external faults, this allows for the detection of a poor sensing-element connection.
If the chip receives an incorrect input level from the sensor, in the arenas of lower than 1.5 V or higher than 3.5 V, possibly the result of a short circuit to ground or to supply, the IC will then generate an output level outside of the clamping-level range. In turn, the ECU detects the event.
Also of interest, this particular interface can program the sensor interface through the actual connector. The module containing the sensing element and the interface are integrated into one housing with only the application pins connected to the outside of the module. It isn’t necessary to add additional communication lines since the output pin acts as both an analog output pin and as a communication pin.
Through short-circuit detection, the IC knows that the user is requesting the pin for communication. To guarantee that no changes to memory parameters occur via a short circuit, a specific timing forms the basis of this detection. Furthermore, the interface chip includes an option to lock the EEPROM to avoid accidentally changing a calibrated device. In essence, by using the output of the interface we can communicate with the chip and calibrate the parameters in EEPROM with user-defined characteristics.
Evaluation boards are available for calibrating the interface. These boards include all the hardware necessary for communicating with the interface, accompanying software, and production software. The production software can control all necessary production equipment and communicate with the device to quickly calibrate hundreds of samples.
APPLICATIONS
Sensor interfaces are ubiquitous in cars. They translate sensor signals into readable language and simultaneously filter out disturbing external elements to ensure the correct message gets sent.
We find sensors of various types in common rail, suspension, and transmission systems as well as in HVAC applications, fuel and gas injection systems, engine control (fuel, oil boost), anti-lock braking systems, and many other areas of the vehicle. They are so widely used that people tend to forget them. Understanding their capabilities will foster the use of these irreplaceable workhorses in an ever-increasing number of applications.
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