Innovative use of MEMS for mid-range pressure sensing

October 21, 2016 // By Graham Prophet
Melexis' (Tessenderlo, Belgium) MLX90819 sensor IC is targeted at measuring mid pressure (10-50 bar) levels; it employs a compact, robust micro-machined solution with accurate sensor functionality, integrated signal processing and analogue or SENT outputs.

Melexis aims to “revolutionize the sector” with this design, applying its MEMS technology to an area that had not been previously adequately served by a fully integrated sensor solution, with system design benefits.

 

Available as a bare die, the MLX90819 runs off a standard 5V supply. It can be employed to accurately determine fluid pressure levels in wide variety of automotive and industrial focused applications. These include the monitoring of engine oil, transmission oil, engine coolant, vehicle fuel lines, air conditioning refrigerant and truck air brake pressures. The IC delivers a relative pressure value. It has a 1 msec response time, plus ±2.5% over life accuracy and ±0.2% linearity across its entire operational pressure range.

 

By using a more advanced process technology, the MLX90819 is able to use a microcontroller based architecture. This allows a much higher degree of sophistication to be incorporated onto the semiconductor die - with all digital processing, data conversion, temperature offset, gain compensation and filtering tasks being taken care of directly. A 16-bit analogue-to-digital converter, 12-bit digital-to-analogue and 16-bit processor core are embedded directly into each sensor IC. The cost and complexity implications of discrete MEMS solutions, as well as the space utilization and sealing wear-and-tear issues that can affect traditional non-MEMS solutions, can be avoided. The IC can deliver either an analogue signal or a single edge nibble transmission (SENT) output for applications requiring a digital output.

 

This robust IC is suited to both heavy duty industrial and automotive deployment, with full AECQ100 compliance and a specified temperature range of -40°C to 150°C. An automotive over-voltage protection mechanism is included in order to ensure ongoing reliability. An array of diagnostic features further support its long term operational integrity. These include analogue output clamping level and broken track detection, plus numerous distinctive diagnostic messages passed via the SENT protocol (such as internal temperature or pressure errors, external over-voltage/under-voltage conditions, etc.) The MLX90819