A modular approach to tyre pressure monitoring systems
04 October 2011
Melexis has recently unveiled its second-generation solution for TPMS.
It combines the MLX91801 Pressure Sensor and MLX72013 RF Transmitter and can be associated to the MLX71122 Multi-Channel RF Receiver in order to build a complete highly integrated solution, compliant with existing Remote Keyless Entry (RKE) systems.
Tyre pressure monitoring is a proven safety enhancement to any vehicle, whether passenger car, light truck, heavy truck or bus. The challenges of meeting regional regulations, and OEM system compatibility, favour modular solutions for most vehicles.
A modular approach pairs the MLX91801, System in a Package (SIP) analogue pressure sensor and sensor interface micro-controller, with an optimised RF Transmitter, the MLX72013. Adding an external roll sensor and peripheral passive support components yields a complete, cost effective, TPMS solution.
The MLX91801 contains blocks for control of the sensor interface, communication interface and power management blocks supporting extremely low power consumption in standby mode. The device measures pressure, temperature and supply voltage. The pressure-sensing element is a MEMS-based absolute resistive bridge pressure sensor. The communication interface provides commands for receiving and sending data to the host system. A standard software library with low-level routines gives access to all the IC’s functions. Application examples provided by Melexis offer an introduction to the Melexis microcontroller programming and allow quick custom developments.
The MLX91801 pressure sensor block offers 1% Full Scale accuracy. The default pressure range is 100 – 800 kPa. Other ranges are available by request.
The MLX72013 ASK / FSK transmitter IC is designed for applications in the license-free 433 MHz ISM (Industrial-Scientific-Medical) band air interface for wireless communications, and 433 MHz is available for use worldwide. It has been designed to meet the latest evolution of the EN 300 220 telecommunications standard; but it can also be used in other countries with similar standards, e.g. FCC part 15.231.
The MLX71122 is a multi-channel receiver IC based on a double-conversion super-heterodyne architecture. It is designed to receive FSK and ASK modulated RF signals either in 8 predefined frequency channels or frequency programmable via a 3-wire serial programming interface (SPI).
Thanks to its highly linear RSSI (Received Signal Strength Indication), the MLX71122 allows for automatic wheel identification, providing users with further integration capabilities.
The block diagram shows the Melexis TPMS solution demo kit that is available. It uses the MLX91801 TPMS sensor, the MLX72013 RF Transmitter IC and the MLX71122 RF Receiver IC. The kit comes with an LF/RF transceiver and antenna, with USB connection to a computer and read out software.
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